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FM 4-115
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Lifcut. Colonel. Tn'rrqtrr
WAR DEPARTMENT
COAST ARTILLERY
FIELD MANUAL
ANTIAIRCRAFT ARTILLERY
OPERATION OF MATERIEL
AND EMPLOYMENT OF PERSONNEL,
ANTIAIRCRAFT SEARCHLIGHT UNITS
FM 4-115
COAST ARTILLERY
FIELD MANUAL
ANTIAIRCRAFT ARTILLERY
OPERATION OF MATERIEL
AND EMPLOYMENT OF PERSONNEL,
ANTIAIRCRAFT SEARCHLIGHT UNITS
PREPARED UNDER DIRECTION OF THE
CHIEF OF COAST ARTILLERY
UNITED STATES
GOVERNMENT PRINTING OFFICE
WASHINGTON : 1940
For sale by the Superintendent of Documents. Washington, D. C. - Price 35 centf*
WAR DEPARTMENT,
Washington, June 20, 1940.
FM 4-115, Coast Artillery Field Manual, Antiaircraft Ar-
tillery, Operation of Materiel and Employment of Personnel,
Antiaircraft Searchlight Units, is published for the informa-
tion and guidance of all concerned.
[A. G. 062.11 (5-1-40).]
By order of the Secretary of War :
G. C. MARSHALL,
Chief of Staff.
Official :
E. S. ADAMS,
Major General,
The Adjutant General.
ii
TABLE OF CONTENTS
Paragraphs Page
Chapter 1. General.
Section I. General 1-5 1
II. Aerial sound ranging 6-12 3
Chapter 2. Training.
Section I. General 13-17 7
II. Selection of personnel 18-23 8
III. Individual training 24-31 11
IV. Section training 32-41 16
V. Platoon training 42-52 22
Chapter 3. Operation and Functioning or
Materiel.
Section I. Sound location equipment 53-58 29
II. Control station 59-61 38
III. Searchlight 62-67 42
IV. Power plant 68-72 46
V. Vehicles 73-77 48
Chapter 4. Preparations for Action and for
Movement.
Section I. Preparing for action 78-94 55
II. Orienting and synchronizing 95-99 75
III. Preparing for the road 100-108 80
IV. Protective measures 109-111 83
Chapter 5. Organization.
Section I. Searchlight battery 112-113 85
II. Searchlight platoon 114-115 85
III. Searchlight section 116-117 86
Chapter 6. Service of the Piece.
Section I. Searchlight platoon action 118-126 90
II. Duties of personnel , 127-129 92
III. Drill of searchlight section 130-143 93
IV. Notes on service of the piece 144-151 104
Chapter 7. Maintenance 152-163 107
Chapter 8. Dril Table 120
Appendix. List op Reference: 121
Index 123
III
FM 4-115
COAST ARTILLERY FIELD MANUAL
ANTIAIRCRAFT ARTILLERY
OPERATION OF MATERIEL AND EMPLOYMENT OF
PERSONNEL, ANTIAIRCRAFT SEARCHLIGHT UNITS
(The matter contained herein supersedes chapter 3 and section
II, of chapter 5, part two; and Table O, chapter 2, part three,
Coast Artillery Field Manual, vol. n, February 1, 1933.)
CHAPTER 1
GENERAL
Section I. General
II. Aerial sound ranging.
Paragraphs
1-5
6-12
Section I
GENERAL
■ 1. Scope. — This manual is designed for use by antiaircraft
searchlight batteries as a guide in the handling of materiel,
selection of personnel, employment of practical training
methods, and service of the piece. Drills and instructions
given pertain especially to the later types of materiel, but
may be applied with slight modification to all materiel of
searchlight units, MVI, M1934, M1937, M1939, and M1940.
■ 2. References. — This manual should be studied in con-
junction with the references listed in the Appendix.
■ 3. General Problem. — The ability of the antiaircraft artil-
lery gun (and in some cases the automatic weapon) battery
to Are effectively on targets at night is dependent upon
artificial illumination of the target so that continuously
pointed Are may be used. This artificial illumination is
furnished by searchlights.
■ 4. Position Finding. — a. The presence of the target is
disclosed by the sound of its motors, propellers, and its
movement through the air. While the sound, when within
the hearing of the unaided ear, will give a general idea of
1
4
COAST ARTILLERY FIELD MANUAL
its apparent direction, this is not sufficient for the pointing
of the searchlight because of the inherent directional inac-
curacy of the human ear. The apparent source of the sound
is constantly moving, and the sound itself is subject to a lag
because of the time necessary for the sound wave to travel
from its source to the point of reception. It is advisable, in
order that the light may be pointed properly, that the sound
be detected at the greatest possible distance, that the target
be followed by its sound, that corrections for sound lag and
other effects be applied, and that a prediction be made of
the true position of the target. Where the searchlight and
the sound locator are so connected together electrically that
the searchlight may be moved with the sound locator in
azimuth and elevation, prediction may be continuous and
automatic. Aerial sound ranging is the process of locating
the aircraft by means of the sound emitted. Aerial sound
ranging is used primarily at night to assist searchlights in
locating targets in order that they may be illuminated with
the minimum delay.
The position of the target is determined when the azimuth,
angular height, and slant range are known. For searchlight
direction, azimuth and angular height only are needed.
b. Any system of position finding and target illumination
at night by means of sound location and searchlight illumi-
nation should —
(1) Determine with the greatest possible accuracy the
angular height and azimuth of the apparent source of the
sound.
(2) Determine the effect of sound lag on azimuth and ele-
vation so that the appropriate corrections may be applied.
(3) Evaluate and apply corrections for the deviating ef-
fects on the sound wave of other known causes.
(4) Determine and apply corrections for parallax at the
target, due to distance between searchlight and sound
locator.
(5) Apply the corrections continuously and without any
loss of time.
(6) Transmit automatically and continuously to the
searchlight the corrected sound locator data.
2
ANTIAIRCRAFT SEARCHLIGHT UNITS
4-7
(7) Move the searchlight continuously in azimuth and
angular height so as* to follow the moving point source of
the sound.
c. The present standard system of target location and
illumination embodies means for accomplishing all except
item (3) of the requirements indicated in b above. No
satisfactory correction device has been developed for deter-
mining and applying corrections for the deviating effects on
the sound wave caused by atmospheric conditions.
d. The method of position finding by sound location is
discussed in connection with the sound locator and acoustic
corrector in paragraphs 7 and 26.
■ 5. Equipment. — a. The complete system for the detection,
location, and illumination of aerial targets includes the fol-
lowing equipment, the arrangement of which is shown sche-
matically in figure 19©:
(1) Searchlight.
(2) Power unit.
(3) Sound locator.
(4) Acoustic corrector (on sound locator) .
(5) Control station.
b. When properly disposed in the field the searchlight is
200 feet from the power unit, the control station is 500 feet
beyond the light, and the sound locator is 900 feet from the
light. The connecting cables between each element are
shown in figure 19®, as follows:
(1) Power cables from power unit to searchlight.
(2) Data transmission cable to searchlight from sound
locator.
(3) Distant electric control cable from searchlight to
control station.
Section II
AERIAL SOUND RANGING
■ 6. General. — See paragraph 4 for a general discussion of
the position-finding problem.
■ 7. Sound Location.— Sound locators are designed to ac-
centuate and make use of the ability of a person to deter -
3
7-9
COAST ARTILLERY FIELD MANUAL
mine the direction of a sound source by means of the binaural
sense. When a man stands in the open where he is not
bothered by echoes, he can determine by his sense of hear-
ing alone the approximate direction of the source of a sound.
He does this instinctively by turning his head so that he will
face the apparent source of the sound. This is largely ac-
counted for by the fact that the human ears are separated
by about 5V4 inches; hence any sound, unless originating in
the perpendicular plane bisecting the line joining the two
ears, will arrive at one ear before it does at the other. The
human ear is sufficiently sensitive to detect this time dif-
ference, and the listener's binaural sense tells him that the
sound originated on the side which the sound first reached.
It is to make the sound arrive at both ears at the same
time (and thus eliminate the time difference) that the head
is instinctively turned until the sound is faced. When the
sound locator is used, the sound source usually appears to
the listener to be directly in rear of his head when the horns
are pointed toward the source.
■ 8. Sound Disturbances. — Sound travels through the at-
mosphere, and the sound waves are affected by every
change and departure from uniformity in the transmitting
medium. The atmosphere itself is always in motion. Any-
thing such as wind, density, or temperature changes which
cause the sound wave to drift or bend will produce an error
in the determination of the direction of the real sound
source and consequently must be corrected for. The most
common causes of the displacement of the sound waves, from
the path and shape which they would have in a still, uniform
atmosphere, are wind drift, wind refraction, and temperature
refraction.
■ 9. Sound Lag. — Sound travels through air of average tem-
perature at about 1,100 feet per second which is less than
half the muzzle velocity of the antiaircraft guns. Sound
may thus be said to have a "time of flight." As the target
continues to move while the sound travels to the locator, the
apparent position of the source lags behind the true position.
This is called the "sound lag." Sound lag depends upon the
slant range of the target when the sound was emitted, the
4
ANTIAIRCRAFT SEARCHLIGHT UNITS
9-12
speed of the target, and the average temperature of the air
which determines the velocity of the sound. At 30° P. this
velocity is 1,022 feet per second, and at 100° P. it is 1,166
feet per second. The velocity changes about 1.1 feet per
second for every degree (Fahrenheit) change of tempera-
ture. For the calculation of sound lag time for various alti-
tudes and angular heights, an average velocity of 1,100 feet
per second can be used without introducing an error of any
consequence. Such a velocity will not be far from the av-
erage since we deal mainly with the lower temperatures after
nightfall and at the higher altitudes. Slant range in feet
divided by the velocity of sound waves in feet per second
gives the sound lag time in seconds.
■ 10. Atmospheric Corrections. — The effects of wind drift,
wind refraction, and temperature refraction on the sound
wave have been discussed. While these effects are known to
exist and while their correction is highly desirable, the prob-
lem of developing a satisfactory correction device has not
been completely solved. The amount of displacement caused
can be computed. However, the basic information on which
these computations must be based is either not available or
is generally quite unreliable.
■ 11. Sound Lag Corrections. — Corrections for sound lag are
determined and applied by the acoustic corrector. The
operation of the corrector in connection with the sound
locator determines and applies the correction for sound lag
to the azimuth and angular height as determined by the
sound locator. These corrected data are transmitted elec-
trically to the control station, enabling the controllers to
point the light in the direction indicated.
■ 12. Parallax Corrections. — a. The location of the various
units of the sound-locating and target-illumination system
is shown in figure 19®. The distance separating the sound
locator and the searchlight will introduce an error into the
data determined by the acoustic corrector because of the
parallax at the target caused by the separation of the two
units of the system. The magnitude of the parallax effect
will depend upon the distance separating the two units, upon
5
12
COAST ARTILLERY FIELD MANUAL
the slant range to the target, and upon the direction of the
target with relation to the line joining the two units.
b. The azimuth parallax correction is of considerable im-
portance in prediction by sound location. The separation
of the sound locator and the searchlight by a considerable
distance is necessary in order to reduce the disturbing noises
which interfere with the operation of the sound locator. It
is desirable that the parallax correction made necessary by
such separation be introduced automatically into the cor-
rected data. The effect of azimuth parallax may be greatly
reduced by setting up the unit with the line searchlight-
sound locator pointed in the direction of the targets' ex-
pected approach.
c. Instructions for computing and applying parallax cor-
rections are given in paragraph 54b.
6
CHAPTER 2
TRAINING
Paragraphs
Section I. General.
II. Selection of personnel.
III. Individual training
IV. Section training
V. Platoon training
13-17
18-23
24r-31
32-41
42-52
Section I
GENERAL
■ 13. Scope. — This chapter contains suggested methods of
selection and training of personnel designed to secure rapid
and efficient illumination of suitable aircraft targets.
■ 14. Importance. — AH active countermeasures against night
flying aircraft, both by pursuit aviation and antiaircraft
artillery, depend on searchlights for the illumination of their
targets. Without this illumination the most elaborate sys-
tem of air and ground antiaircraft defense is useless.
■ 15. Targets. — a. Antiaircraft searchlights are primarily
designed to illuminate aircraft flying at medium and high
altitudes — normal targets for the antiaircraft gun. Their
additional mission is to illuminate low-flying aircraft — those
which are the normal target for automatic weapons. Pri-
mary targets must be illuminated at such a distance from the
objective as will permit the fire-control instruments of the
gun batteries involved to pick up the target and track it,
and the guns to open fire so that the first shells burst at
the maximum effective range of the guns.
&. Antiaircraft searchlights also cooperate with friendly
aviation by illuminating targets for pursuit aircraft, enabling
the friendly pursuit to find and attack the enemy.
■ 16. Locating the Target. — The short time available for
tracking the target prior to illuminating it makes it im-
perative that the methods used in locating the target be
i
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COAST ARTILLERY FIELD MANUAL
simple, accurate, and rapid. Practice in locating targets
should include training to identify, as well as locate, the
target by sound. The theory underlying these methods of
target location is discussed in detail in PM 4-111.
■ 17. Selection and Training of Personnel. — Efficient op-
eration of searchlight materiel requires that personnel be
carefully selected and thoroughly trained. In order to allow
for inevitable losses due to promotion, sickness, and casual-
ties, each keyman must have at least one understudy trained
as his replacement. Selection and training of personnel are
discussed in detail in the following sections.
Section II
SELECTION OF PERSONNEL
■ 18. Listener Qualifications. — The men of the searchlight
battery who must be most carefully selected are the listeners
who operate the sound locators. They must have good
hearing, be alert, be able to concentrate without tiring, and
possess at least a normal ability to locate the direction of
the source of a sound (binaural sense) .
■ 19. Test of Hearing. — The first step in selecting listeners
is to give every available man in the battery an examination
in hearing. This should be performed by a medical officer
using an audiometer. A record should be kept and the men
classified as follows: those with 20/20 hearing in both ears,
those who do not have balanced ears, and those who have
poorer than 20/20 hearing. Men who do not possess satis-
factory acuity of hearing in each ear, and who have not
approximately the same acuity in both ears, should not be
selected as listeners.
■ 20. Binaural Test. — a. The second step in selecting lis-
teners is to give all those men having normal or better hear-
ing a test for their ability to locate a sound source accu-
rately (binaural sense). This test is performed on the
binaural training instrument, Ml or M2. (Pig. 1.) Before
making this test, however, it is important that the candi-
dates be given a clear idea of what is meant by locating a
sound, using the binaural sense, and how it differs from lo-
8
ANTIAIRCRAFT SEARCHLIGHT UNITS 20-21
eating it using the intensity sense (the difference in loudness
in each ear).
b. (1) The following demonstration will show how the
binaural sense functions and how it differs from the inten-
sity sense. A group of 10 to 20 men is arranged in a large
circle, facing inward, and with eyes closed. The instruc-
tor takes position just inside the circle and calls on various
men by name to point to him, locating him solely by the
sound of his voice. After the men have the idea, one-half
the men. are allowed to watch the other half locate the
instructor by sound. This will not only give all an idea of
what is meant by locating a sound, but will show that prac-
tically all men possess this sense.
(2) After all men have demonstrated their ability to lo-
cate a fixed sound (instructor standing still) the instructor
moves around inside the ring, talking as he moves, and call-
ing on various men to follow him with their pointing fingers
as he moves. This will give the idea of following a moving
target. Having one-half the class look while the other half
works will show how easily all men follow the moving sound.
(3) The next step is to prove that this sound locating
ability does not depend on the fact that one ear hears the
sound louder than the other. One blindfolded man is di-
rected to cover his left ear with his hand lightly, so that
he can still hear with his left ear but not as well as with his
uncovered right ear. The instructor speaks while on the
left of the man and directs the man to point in his direction.
The man will point in the correct direction (to the left).
It is then explained that if we located sounds by the in-
tensity (loudness) of the sound, the man would have lo-
cated the sound as nearest his uncovered or right ear (to his
right), as this ear heard the sound with greater intensity
(louder) than did the covered left ear. Each man is then
given the opportunity to try this test, some covering the
right ear, some the left.
■ 21. Distant Test. — The binaural training instrument, M2,
includes a horn assembly rigged up on an elevated wire so
that it may be moved back and forth at will. All candidates
are given an opportunity to follow the sound at varying dis-
tances so as to get practice at a greater distance than is
9
21-22 COAST ARTILLERY FIELD MANUAL
possible in the circle. During all these tests the candidates
should be marked on alertness, accuracy, and general ability
to do what is indicated.
Figure 1. — Binaural training instrument, Ml.
■ 22. Binaural Trainer Test. — The binaural training instru-
ment (fig. 1) affords a means of measuring binaural ability
numerically and therefore is very convenient for comparing
the ability of the various candidates. Each candidate is
given a few trial runs to make sure that he knows what is
required. As the candidate turns the handwheel, the sound
will seem to move across the back of the skull from one ear
to the other. When the sound is properly centered, it
should seem to be at the base of the skull, midway between
the two ears. In some observers the sound will seem to be
coming from the front — in others from the rear, but this
is an individual idiosyncracy and has no effect on accuracy.
The important requirement is that the sound be centered
10
ANTIAIRCRAFT SEARCHLIGHT UNITS 22-24
midway between the ears and at the same place on every
trial. Most learners find it helps to bracket the sound, that
is, move the wheel until the sound seems to be a short
distance on one side of center, then move the wheel in the
opposite direction until the sound is definitely nearer the
other ear, and then split the distance between the two posi-
tions. After the trial runs have been completed, the candi-
date should be given at least five test runs on a fixed sound
source (instructor's handwheel not moved during test) , and
the results recorded. Next the candidate is given several
trial runs at a moving sound source (instructor's hand-
wheel slowly and evenly moved by instructor during test).
The candidate endeavors to keep the sound centered during
the test by moving his handwheel the proper amount and
in the proper direction. At least five test runs are then
made and the results recorded.
■ 23. Sound Locator Test. — As a result of the tests leading
up to and including the binaural -trainer test, the number
of candidates should be cut down to about three listeners
per position available. Those selected should be tested on
the sound locator. As a sound source, the loud-speaker
equipment of the binaural trainer, M2, or a moving truck
or car at a distance of 100 yards or more affords a good
substitute for an airplane, without introducing the compli-
cations of sound lag. As a result of these tests, the number
of candidates should be reduced to about double the number
of positions available. With these listeners, individual train-
ing is commenced.
Section III
INDIVIDUAL TRAINING OF PERSONNEL
■ 24. Phases. — The training of personnel is divided into
three phases : individual training, unit training, and platoon
training. In the first phase, individuals are perfected in the
technique of their individual duties. In the second, the men
manning one searchlight unit (light, locator, power plant,
and vehicles) learn to work together as a team. In the third
phase, the light units composing a platoon work together as
a team to pick up and carry single and multiple airplane
targets.
11
25-26
COAST ARTILLERY FIELD MANUAL
■ 25. Listeners. — a. Having cut the number of candidates
to twice the number needed to man the sound locators, the
unit may proceed to individual training. The listeners
should first be given further training on the "buzzer on the
wire" and the binaural trainer, both of which may be used
indoors if desired. This should be followed by training on
the locator, first on a vehicle target at short ranges (100-500
yards) and later on airplane targets at increasing ranges.
Here the instructor may use considerable initiative in se-
curing suitable targets by setting up the locator near an
airfield, near a road along which automobiles travel, or near
the shore where power boats are in use.
b. Once the listeners clearly understand what is required
of them, it is only necessary to afford them sufficient oppor-
tunity for practice in order to obtain efficient performance.
They should listen on every conceivable target: pursuit
planes, observation planes, bombing planes; one-, two,- and
four-motored planes; planes flying singly and in formation.
c. As air commanders expect to "screen" their high-flying
bombers by lower-flying formations of other planes, the lis-
teners must be trained to pick up the bombers through the
screen. As the screen will generally be composed of aircraft
other than bombers, this operation is entirely practical.
d. Listeners should be trained to identify targets by means
of the sound heard. A two-motored flying boat will make a
very different sound from that made by a two-motored
bomber. Two single-motored planes flying close together
can be distinguished from one two-motored plane. Planes
with liquid-cooled engines which have an even number of
cylinders can be distinguished from those with air-cooled
engines which are generally made with an odd number of
cylinders. Engines of different size emit different sounds.
■ 26. Acoustic Corrector Operators. — To permit the fre-
quent relief of listeners, the acoustic corrector operator is
normally an alternate listener.
a. The operator is given some idea of the sound lag prob-
lem so that he will understand the importance of his correc-
tions in the transmission of accurate data to the searchlight.
12
ANTIAIRCRAFT SEARCHLIGHT UNITS
26-27
(1) As shown in figure 2, the target may travel as much
as a mile between the time a sound was emitted and the
time it reaches the listener on the ground. So while the
sound indicates that the target is at its apparent position in
the figure, it is actually at its true position.
(2) The acoustic corrector determines and applies the
correction for sound lag, so that, although the locator is
pointed at the apparent position, the searchlight will be
pointed at the true position.
b. The operator is also shown his duties in the actual
operation of the corrector (pars. 54 to 56, incl.). He is
practiced in the movements necessary to operate the cor-
rector until he acquires a reasonable mechanical skill.
c. He is given a general idea of the sequence of events in
picking up the aerial target, so that he will not be confused
when the equipment is operated together as a unit. (See
par. 36.)
LOCATOR
Figure 2. — Sound lag correction.
■ 27. Telephone Operators. — a. The primary qualifications
for a telephone operator are good hearing and the ability to
speak clearly and correctly. Most men do not have the
second qualification naturally but must be trained in speech.
The pronunciation of numbers for telephone use ("fo-wer"
for four, "ni-yen" for nine, etc.), the use of words to indi-
cate letters of the alphabet ("affirm" for A) , and the general
235203° — 40 2
13
27-28
COAST ARTILLERY FIELD MANUAL
procedure for efficient telephone operation as given in PM
24-5 should be included in the training.
b. In addition to the general training mentioned above,
the operator should be afforded a great deal of practice in
the use of words, commands, and warnings usually employed
in the searchlight platoon. A series of hypothetical com-
mands, warnings, and messages simulating actual operations
will help the new operator to become familiar with the type
language used by the searchlight organizations.
c. As speed is the most important factor in antiaircraft
communication, the operator does not ordinarily record the
message received, but repeats the message orally as it comes
over the wire. Similarly, messages from the chief of section
to the platoon command post are not recorded but are re-
peated as given by the chief of section. Exception is made
in the case of administrative messages (messages relating to
supplies, repairs, etc.) where speed is not a consideration,
and a copy of the message is desired.
d. A general idea of how the telephone works and how to
make simple repairs should be given the operator. He should
have practice in diagnosing simple troubles in the telephone
line and in recognizing the symptoms of a short circuit, an
open circuit, or other source of trouble. For details see PM
24-5.
■ 28. Control Station Operators. — a. (1) The azimuth and
elevation controllers should be trained to keep the search-
light pointed as indicated by the sound locator. This is
accomplished by using the handwheels to keep the zero
readers centered. They should be cautioned to avoid radical
movements and to smooth out any sudden movements called
for by the zero readers. They search for the target by
slowly and smoothly moving the zero reader pointers first to
one side and then to the other side of the zero mark.
(2) The searchlight commander (generally a noncom-
missioned officer) looks through the binoculars and directs
the search for the target. He should be instructed as to the
size of the area of error through which the controllers
search. This area of error may be assumed as 10° in di-
ameter (searchlight beam is about VA° in diameter) for a
14
ANTIAIRCRAFT SEARCHLIGHT UNITS
28-30
new locator crew and 5° for an experienced locator crew. He
is then shown how to use the binoculars on the control sta-
tion in an active search and how to carry the target after
it is picked up. He should be instructed as to the importance
of a slow and careful search, as many unseen flicks are made
because the search was too fast and the flick too short.
b. The details of the actual operation of the control sta-
tion are given in paragraphs 59 to 61, inclusive.
■ 29. Searchlight Operators. — a. The searchlight operator
should be trained in all the details pertaining to the func-
tioning of the searchlight. He should be taught the pre-
scribed method of —
(1) Leveling the light (par. 64).
(2) Orienting the light (pars. 96 to 99, incl.) .
(3) Striking the arc (par. 63c) .
(4) Adjusting the arc length (par. 63/) .
(5) Keeping the positive crater at the focal point of the
mirror (par. 63e).
(6) Keeping the arc voltage and current at the proper
values (par. 63e) .
(7) Recarboning the light (par. 65).
(8) Cleaning the light (par. 155).
(9) Lubricating the light (par. 156).
b. It is important that the light operator be given suffi-
cient instruction and drill on the manual control of the
searchlight and its arc, in order that the change from auto-
matic to semiautomatic or manual control may be made
without confusion and loss of efficiency. Even though the
automatic devices usually function perfectly, complete reli-
ance must not be placed on them.
c. Detailed instructions for the operation of the search-
light will be found in paragraphs 62 to 67, inclusive.
■ 30. Power-Plant Operators. — a. Each power-plant oper-
ator is first trained in the mechanics of starting, running,
and stopping the power-plant engine. He is then trained to
operate the power panel and to keep the power plant in
good operating condition.
b. He is thoroughly trained in the manual operation of the
power plant to insure its continued operation in case the
15
30-33
COAST ARTILLERY FIELD MANUAL
automatic devices fail. Manual operation requires frequent
practice and a high degree of mechanical skill to operate
the power unit efficiently.
c. Detailed directions for power-plant operation are found
in paragraphs 68 to 72, inclusive.
■ 31. Chauffeurs. — a. The majority of enlisted men today
have had some experience in driving an automobile. They
should be first taught the difference between a passenger car
and the truck they are to operate. The difference in height,
length, and weight should be pointed out so that they will
not attempt to drive the truck through an opening too small
for it. The greater length will make it impossible to get
around hairpin turns easily negotiated with a car. The
greater weight calls for greater care as to bridges tried and
muddy roads used.
b. New chauffeurs should be taught the care of the truck —
how to replace gasoline, oil, water, battery water, and air in
the tires; how often to check these items; and how to lubri-
cate the truck. (See FM 25-10.)
c. They should be given an understanding of what not to
do; that they should not adjust the carbureter, adjust the
breaker points, clean the spark plugs, or attempt to make
other repairs normally attended to by the battery mainte-
nance section.
Section IV
SECTION TRAINING
■ 32. Scope. — The training of the section should provide in-
struction in the teamwork of operating one complete search-
light unit efficiently.
■ 33. Method. — a. Given proper individual training, the
most important factor in unit training is practice. Practice
must be at regular intervals and cover all the different situa-
tions the unit is likely to encounter in action.
b. The importance of frequent practice at regular intervals
cannot be overemphasized. It has been found that a break
of a few days in training seriously lowers the efficiency of a
unit. To prevent these breaks in training, the unit com-
16
ANTIAIRCRAFT SEARCHLIGHT UNITS
33-35
mander must use all possible ingenuity. The binaural training
instrument, M2, motor vehicles, motor boats, and commercial
and military airplanes must constantly be employed to fill in
the periods where no regular drills on assigned targets are
possible.
■ 34. Chiefs of Section. — Chiefs of section require careful
training in order to be able to operate their units properly.
Their training should include the subjects listed below.
a. Acoustics should be covered in enough detail so that the
chief of section can understand and explain —
(1) Travel of sound in air, and how its speed varies with
temperature.
(2) What sound lag is, and why we correct for it.
b. Atmospherics should include an idea of the general
formation of the atmosphere, how its density varies with
altitude, why winds from various directions affect the read-
ings of the sound locator, and the corrections to apply for
winds from various directions.
c. Map reading is essential, as the section commander
must be able to tell from a map —
(1) How to get to a position marked on the map, or the
coordinates of which are furnished.
(2) Whether a road is too steep for his light vehicles to
climb.
(3) Whether a nearby knoll is high enough to blanket a
prospective light position.
d. Tactics and speed of modern aircraft of the different
types.
e. Selection of a good searchlight position as described in
paragraph 80.
■ 35. Searchlight Commanders. — a. The principal emphasis
in the training of the searchlight commander should be
placed on the search for the target. He should know enough
of illumination phenomena and sound phenomena (FM
4-111) to understand why a search is necessary, how large
an area should be searched, and why it is necessary to search
slowly. As a result of experience with his particular light
unit crew, he should be taught exactly how large an area to
17
35-36
COAST ARTILLERY FIELD MANUAL
search and how to apply corrections for individual listeners'
errors.
b. He should know enough about the design and function-
ing of the searchlight, control station, and power plant to
supervise their operation and routine maintenance.
c. He should be trained to be able to take over the duties
of the chief of section, should this become necessary.
■ 36. Listeners and Acoustic Corrector Operators. — a. On
a normal course, the operators will find that events will
occur in the following sequence:
(1) The listeners at advanced listening posts (several
miles to the front) will report a target coming in and its
general location as to azimuth and estimated altitude.
(2) Aided by this report, the chief of section directs the
listeners to move the locator horns to the general direction
indicated and to search (move the horns up and down, right
and left) in that general vicinity. In the usual case, it will
be possible to hear the target with the unaided ear before
picking it up with the locator. Coached by the section
chief, the listeners pick up the target in their horns. As
each listener centers the sound of the target, he reports "On
target." This will generally occur when the target is be-
tween 10° and 20° above the horizontal.
(3) At the section chief's command track, the acoustic
corrector operator operates his instruments, sending cor-
rected sound locator data to the light.
(4) At the command in action given by the chief of
section (normally by whistle), the light is turned on and a
search for the target begun. This command is generally
given when the target is from 30° to 45° above the hori-
zontal. During this searching period, the listeners and cor-
rector operators continue as before, sending corrector data
to the control station.
(5) The target will next be picked up and carried. The
listeners and operators cease tracking and turn the locator
to the front, ready for another target.
(6) At the command out of action, the light is put out.
6. It is important that the listeners center the sound at
the same place each time, that is, midway between the ears,
18
ANTIAIRCRAFT SEARCHLIGHT UNITS
36-37
leaving the section chief to determine and apply the correc-
tion necessary for the particular individual. Every oppor-
tunity must be taken to check on this individual correction
as it is subject to a gradual change especially while a listener
is learning. This checking may be done whenever the
listeners are tracking a target, and the target may be seen
by looking through the open sight on the light. If the target
is not seen at the center of the sight, and this difference (or
individual correction) remains approximately constant from
day to day, it should be recorded and applied whenever that
listener is on duty.
c. As an aid to training the locator corrector crews, the
light units can be set up (at night) close to each other. The
target plane is directed to leave its running lights on. The
lights are pointed on sound locator data. The amount the
light beams miss the target is an indication of the error of
the sections. The gradual decrease in the size of this error
as training progresses is of considerable encouragement to
the crews of the various units and injects a competitive
spirit into the training.
d. The listeners are using a delicate sense (the binaural
sense), and when operating accurately are differentiating
between the time of arrival of the sound at the left and the
right ears by 1/30,000 of a second. Anything that interferes
with their physical and mental well-being, whether worry,
alcohol, or lack of sleep, will be reflected immediately in the
quality of their work.
■ 37. Determination of Individual Corrections. — a. It is in
the latter part of section training that the individual cor-
rections for each regular and alternate listener are obtained.
b. This determination is best made at night. The search-
light is placed in action and on the target plane. The lis-
teners, blindfolded, track the target. The acoustic-corrector
operator functions normally. If the listener has no indi-
vidual correction, the zero-reader needles should remain
centered, as the light is kept on the target plane and the
locator is indicating the direction of the target plane. Any
difference is caused by the idiosyncrasies of the listener and
the nonstandard condition of the atmosphere. However,
19
37-39
COAST ARTILLERY FIELD MANUAL
when determinations are made on several nights with dif-
fering atmospheric conditions, an average correction may be
arrived at which is usable and which will increase the accu-
racy of the unit. The accuracy of operation may be illus-
trated graphically by keeping the target planes' lights on
and pointing the lighted searchlight on locator data.
c. On units having zero readers, this correction can be
recorded as so many "needle widths" right or left of center.
The two controllers then use this point, instead of the zero
of the zero reader, as the point about which they search.
d. On units employing the sound locators, M1A1 and
M1A2, this correction may be applied as an arbitrary correc-
tion directly to the acoustic corrector.
e. The operation of the locator acoustic corrector com-
bination may be tested without the presence of light and
control station. The target plane keeps its lights on. The
locator and corrector are operated normally. If operation
is accurate, target and pantograph pointer will be lined up
with the cross lines in the mirror, providing no parallax
correction has been applied. The amount they are out of
line is a measurement of the error.
■ 38. Chauffeurs. — a. The chauffeurs will receive most of
their training as they move their vehicles from place to place
during the training of the section.
b. During this training, the chiefs of section will have
ample opportunity to point out the necessary expedients to
the new chauffeurs. The mechanics of how best to drive
when operating without lights, particularly, how to back up
for 900 feet in order to pick up the blue cable, and how to
turn around in a restricted space, should all be practiced
during this period.
c. The importance of camouflage is pointed out, and prac-
tice is given in selecting suitable parking places where nat-
ural camouflage is sufficient. Practice in artificially cam-
ouflaging the truck should be given. For more detailed in-
structions see FM 4-105 and PM 5-20.
■ 39. Other Members. — The training of the other members
of the section is devoted to fitting the skill they have ac-
quired in individual training into the teamwork of the unit.
20
ANTIAIRCRAFT SEARCHLIGHT TWITS 39-41
Their training is not dependent upon an aerial target and
can be carried on almost as well indoors as out and in day-
light as well as dark.
■ 40. Indoctrination of Personnel. — The whole searchlight
organization depends on the accuracy of the sound locators
for its efficiency. To use the searchlight team at its maxi-
mum effectiveness it is necessary that all concerned place
their confidence in the sound locators, and believe that the
data sent from the locators are reasonably accurate. The
crews must also believe that the sound-locator data are
more accurate than the guesses made by personnel using
the unaided ear. This matter is important enough to war-
rant a special daylight test or demonstration before the
whole battery. For the demonstration a complete unit is set
up. The listeners and several selected noncommissioned
officers and privates are blindfolded. A target appears.
During the course the searchlight is pointed on sound loca-
tor data, and its closeness to the target observed in the
open sight on the light. At the same time, the unaided
listeners stand beside the light and indicate the direction
of the target. The reaction of the rest of the battery to
their inaccurate efforts to point out the target will usually
indoctrinate all with the idea that locator data are best.
In the absence of such a demonstration and constant indoc-
trination by the instructors, the noncommissioned officers
will tend to revert to the use of their own ears when under
stress, to the complete confusion of the unit.
■ 41. Daylight Preparation. — a. In order to train the en-
tire section to function as a unit prior to working under the
handicap of darkness it has been found valuable to train
the section a few times during daylight. The equipment of
the entire section is set up and the listeners are blindfolded.
The procedure used is the same as though the training was
being carried on at night. The accuracy of the work can be
judged by looking through the sights on the searchlight and
seeing how near the target the light is pointed.
b. This set-up gives the battery officers and the section
chiefs a chance to observe the work of each member of the
21
41-44
COAST ARTILLERY FIELD MANUAL
section and of the section as a whole. For this training all
the sections of a platoon and all platoons of a battery may be
assembled at a central location. The sections should be set
up in a line with an interval of about 10 yards between sec-
tions. An airplane should fly courses starting at least 5 miles
beyond listening range and passing over the line of lights
on each course. The early courses should be at low altitude
(4,000 ft.) and the altitude increased progressively as the
training of listeners improves until service altitudes of from
12,000 to 18,000 feet are reached.
Section V
PLATOON TRAINING
■ 42. Scope. — The platoon training should instruct the light
units in the teamwork of operating efficiently with other
light units.
■ 43. Phases. — The training of the platoon can be divided
into two phases, primary and advanced.
a. The primary training phase affords an opportunity for
the previously trained light units to work together in pick-
ing up a single target in the shortest possible time. Prac-
tice is the most important single factor. Night practice is
best, but daytime practice with listeners blindfolded is
valuable.
b. The advanced training phase affords an opportunity to
drill the light units in functioning under more difficult serv-
ice conditions. Multiple targets, interference by low flying
pursuit aviation, functioning without communications, and
functioning while being attacked by low flying bombardment
come under this classification.
■ 44. Normal Situation. — a. The normal set-up for a
searchlight defense is shown in figure 3. Distances between
lights, and between the advanced listening posts and the
forward lights, will be found in FM 4-105. The normal com-
munication net is described in the same manual. One bat-
tery is required to afford all around defense of the objec-
tive. The platoon command post is generally located at the
center light in the forward line. Reports come in from the
22
ANTIAIRCRAFT SEARCHLIGHT UNITS
44
advanced listening posts through the forward lights to the
platoon command post. Those reports necessary are relayed
to the gun battery in the defended sector. The platoon com-
mander issues orders and information over the telephone
lines from the command post to the several lights.
b. The advanced listening post (observation post) is
manned by an observer (or observers) . The only equipment
required is a field telephone.
A
Figure 3. — Antiaircraft artillery defense of an objective.
23
45
COAST ARTILLERY FIELD MANUAL
■ 45. Sequence op Events. — a. (1) If the searchlight pla-
toon is part of a highly organized defense, it will probably
secure advance information of the approach of enemy planes.
If not, or if the enemy planes elude detection, the platoon
must depend on its own advanced listening posts. These
posts, illustrated in figure 3, should give the following data
on the enemy planes heard:
(a) Identification number of post reporting (post No. 2) .
(b) Number of planes heard (one or five or many) .
(c) Type of planes heard (pursuit or bombers) .
(d) Location of plane (to the right, overhead, or to the
left) .
(e) Estimated altitude in thousands of feet (altitude 15) .
(/) Direction of travel (north, northeast, east, southeast,
etc.) .
(fir) Time target was heard.
(2) A specimen telephone message would read, "Post No.
2, many bombers overhead, altitude 15, traveling southeast,
0939." If advanced post No. 2 reports the target as over-
head, post No. 1 to its left, and post No. 3 to its right, the
location of the target is fairly well fixed.
b. Soon after the advanced posts have reported, the first
hum of the advancing planes will be heard at the forward
light positions, when they seem to be at an elevation of
5° to 15° above horizontal. The sound locators, which have
been previously traversed to the direction reported by the
advanced posts, commence an active search for the target.
c. (1) When the chief of section of the nearest pick-up
(forward) light estimates that the target is in a favorable
position for the pick-up (at an elevation of 30°-45°), he
commands: IN ACTION. The other pick-up lights in range
go into action immediately and assist the first light to pick
up the target.
(2) When the defense is trying to pick up two targets,
the procedure is quite similar to that outlined above. The
chiefs of section must be sure in assigning a target to select
the target most nearly in front of them and avoid assign-
ing targets off on their flanks. Those chiefs of section lo-
cated between two targets must exercise judgment as to
24
ANTIAIRCRAFT SEARCHLIGHT UNITS 45-47
which of the two targets to assign, as otherwise too many-
lights will be searching for one target and too few for the
other.
d. After pick-up, the nearest two carry (rear) lights place
their beams on the target and carry it. The pick-up (for-
ward) lights go out of action (if no new target is heard)
or change target.
■ 46. Planning. — a. After an aerial night attack commences,
only a very limited time will be available in which to issue
orders. Therefore to insure efficient cooperation between
the lights during an attack, the procedure to be followed
must be worked out before the light sections proceed to their
assigned positions. Initiation of action must be based on a
few simple plans.
b. After the various forms of enemy attack have been
visualized, and suitable means of combating them have been
devised, the light unit commanders and later the light units
must be drilled over and over again until their response to a
given situation is quick and without confusion.
c. The exact procedure to be adopted will depend on
enemy tactics, the prevailing weather, the strength of the
defense, and other factors of the moment. However^ certain
general rules may be laid down.
■ 47. Notes on Operation. — a. All pick-up (forward) lights
within pick-up distance of the target and not needed else-
where will go into action when the target comes in range.
b. After pick-up, two carry (rear) lights carry the target.
All others go out of action, swing around to the front, and
await the next target.
c. If two targets come in simultaneously, two or three
pick-up lights search for one target and two or three for the
other. If more than two are heard in a narrow sector, it is
better to disregard the others and concentrate on picking
up two.
d. Any pick-up light in range whose sound locator or
distant electric control (D. E. C.) fails should search in the
region being covered by the other lights.
e. If the distant electric control fails, the extended hand
control should be immediately connected and used.
25
47-49
COAST ARTILLERY FIELD MANUAL
/. Where no- wire communication between lights exists,
lights always go into action on the initiative of the section
chief. When one light starts a search, the other pick-up
lights within range go into action immediately and assist.
■ 48. Moving Situations. — a. Whenever the antiaircraft
artillery defense is acting in a mobile situation, it is neces-
sary to plan ahead and anticipate the next move. This is
especially true in situations where no telephone lines have
been laid.
b. When the antiaircraft artillery is part of the field forces
in combat, it is necessary to have prepared plans for a for-
ward and a retrograde movement. A simple signal from the
command post searchlight will then direct the movement in
the desired direction.
c. Roundabout communication can often be secured by
sending a message via the nearest field artillery telephone
net. This is likely to be rather slow if the Field Artillery
is busy at the time.
d. It will often be necessary to rely on a motorcycle mes-
senger to deliver messages and orders to the various lights.
The platoon commander should visit each light unit and
talk over the situation with the light unit commanders at
least once during the day.
e. Situations will arise where it is not wise to have the
light units take the road to a central bivouac. In this case
it will generally be possible to attach the men of each light
to the nearest artillery or infantry unit for rations.
/. There is scarcely any type of military work that makes
greater demands on the noncommissioned officer than the
command of an antiaircraft searchlight unit, especially in a
moving situation. He must understand something of acous-
tics, electricity, gasoline motor vehicles, power plants, map
reading, messing, and supply. The only way the platoon
commander can be sure that the necessary knowledge is
acquired is to train the unit commanders and then try them
out in simulated war situations.
■ 49. Carrying the Target. — When an illuminated target
flies across a defended area, it must be passed from carry
light to carry light, always keeping two lights on it. This
26
ANTIAIRCRAFT SEARCHLIGHT UNITS 49-51
should be done without orders. In order that all concerned
may know what is expected, the maneuver should be fre-
quently practiced.
■ 50. Bomber Formations Screened by Other Aviation. — a.
The enemy will endeavor to place his low-flying aviation
between the sound locators and the high-flying bombers.
A pursuit formation directly in line with the bombers and
close above the sound locators will drown out the sound
made by the bombers, but only momentarily. During this
moment when one locator is blanketed, the other four of
the platoon are little interfered with.
b. When the screening formation flies close to the bomber
formation, reliance must be placed on the difference in sound
between the bombers and the screening planes. Large planes
will seldom if ever be used for screening, as they could be
more efficiently employed to carry bombs. It is unlikely that
the screening formation will be immediately below the bomb-
ers, as they would then be in danger from the falling bombs.
■ 51. Gliding Targets. — a. The purpose of gliding in to the
objective is to reduce the noise made by the motors and
propellers of the attacking airplane and thereby avoid de-
tection. If the light units are located in a very noisy area,
or if the light crews are poorly trained, this gives good re-
sults. Against a well-trained crew, these tactics are almost
sure to fail.
b. During the glide, the motors are not turned off and the
propellers stopped, but the motors are allowed to idle, which
means that the propellers will be rotating at a speed of 400
revolutions per minute or more. Each time a blade comes
opposite the wing it creates a characteristic "whosh" which
is easy to identify and center, using the sound locator. .
c. Combating glide bombers calls for greater alertness on
the part of the advanced listening posts. They must hear
the gliding airplanes and report to the command post, as
otherwise the planes will be over the lights before their
presence is realized. As these posts are several miles in ad-
vance of the lights, they may be able to hear the planes
approaching before they start their glide.
27
51-52
COAST ARTILLERY FIELD MANUAL
d. Once the locator is "on target," the procedure in
searching, picking up, and carrying is the same as for a
normal target.
■ 52. Daylight Training. — a. It will rarely be possible to
have an airplane target at the disposal of the searchlights
whenever desired. After the first few days of training, flying
time is most profitably employed at night. During the day,
use should be made of chance targets to train the light unit
crews.
b. Advantage should be taken of any nearby commercial
air route, airport, military airport, or military air training
area to furnish chance targets. A call to the commercial air-
port will ascertain the commercial schedules, student train-
ing, and other definite flying in progress. The nearby Army
and Navy air fields will generally supply a copy of their
training schedules in advance.
c. Failing impromptu air activity, use may be made of a
nearby highway or water area where automobiles or motor-
boats furnish moving targets to track.
d. When weather is inclement, the "loudspeaker on a
wire" at the far end of a large garage may be employed. If
this is impracticable, the listeners may be drilled on the
binaural trainer. This training may be enlivened by em-
ploying some outside noise such as a nearby electric fan to
simulate a screen of low flying planes.
e. During daylight training, the listeners should be blind-
folded as the effort to keep the eyes closed is distracting.
28
CHAPTER 3
OPERATION AND FUNCTIONING OF MATERIEL
Paragraphs
Section I. Sound location equipment 53-58
II. Control station 59-61
III. Searchlight 62-67
IV. Power plant 68-72
V. Vehicles 73-77
Section I
SOUND LOCATION EQUIPMENT
■ 53. Operation of Sound Locator, M2. — a. This locator has
three composition horns mounted on a pedestal and base.
The acoustic corrector is built into the sound locator. One
horn has been eliminated by using a common horn for both
elevation and azimuth. As shown in figure 4, the elevation
and azimuth listeners stand, one in front of and one in rear
Figure 4. — Sound locator, M2, in operating position.
21. Azimuth horn. 24. Elevation listener.
22. Common (azimuth -elevation) horn. 25. Azimuth listener.
23. Corrector operator. 26. Elevation horn.
235203°— 40 3 29
53-54
COAST ARTILLERY FIELD MANUAL
of the locator. They track the target by turning hand-
wheels provided.
b. This locator incorporates several improvements based
upon experience in using the M1A1 sound locator. The
horns have composition walls, so that all noises coming from
the sides or rear of the horns are deadened and are not
heard. The mouths of the horns are rounded, so that the
wind does not whistle as it blows across them.
c. The complete locator weighs 975 pounds (including
case, cable, and reel) and is broken up into six loads, the
heaviest of which weighs 350 pounds. It can therefore be
carried in the body of any truck and can be manhandled
Into any operating position desired.
d. Several steps must be taken before the locator is ready
to furnish data to the searchlight.
(1) The locator must be assembled in its operating posi-
tion, leveled, and connected by cable to the searchlight as
described in paragraph 88.
(2) It must be oriented and synchronized with the con-
trol station and the searchlight as described in paragraphs
96 to 99, inclusive.
(3) It must be prepared to track the target as described
in paragraph 55.
■ 54. Operation of Acoustic Corrector on Sound Locator,
M2. — This corrector is an integral part of the M2 sound
locator and requires one operator.
a. Wind corrections. — The corrector, illustrated in figures
6 and 7, has provisions for incorporating corrections for
parallax. The correction for wind effect, parallel to the
target's course, is automatically taken care of when the air
speed of the target is set in, and that at right angles to the
target's course is disregarded.
b. Parallax corrections. — Parallax corrections are made by
rotating the parallax cam. This cam is graduated in refer-
ence numbers from to 10. The proper correction to be
applied is determined in figure 5. For example, when using
a 900-foot base line between the sound locator and search-
light, if the estimated slant range to the searchlight pick-up
is 18,000 feet, the parallax offset should be 4 on the parallax
scale as shown by the intersection of the dotted line with a
900-foot base line. These corrections are set in before track-
30
ANTIAIRCRAFT SEARCHLIGHT UNITS
54-55
ing is begun. During tracking, the acoustic-corrector oper-
ator keeps the pantograph pointer ((11), fig. 6) centered in
the cross at (12) by looking through the peep sight. He
accomplishes this by turning the correction handle ((34),
fig. 26) for azimuth control and by rotating the correction
Figure 5. — Graph ol parallax settings.
knob at the extremity of the above handle for elevation
control. By keeping this pantograph pointer so centered,
the operator automatically sets in the corrections for sound
lag, wind, and parallax.
■ 55. Preparations Before Tracking the Target. — a. Set in
the estimated target air speed by means of knob ((2) , fig. 6) .
This information is obtained by the battery commander from
the outpost listening stations, from his knowledge of the
expected type of target, or it is estimated by the chief of
section.
b. Set in parallax offset on scale (15). This information
is obtained by the battery commander from the graph in
figure 5.
c. The corrector operator ((23), fig. 4), will then take
his place at the sight.
31
55
COAST ARTILLERY FIELD MANUAL
d. The listeners will, in the meantime, don their helmets
and adjust the straps to provide for maximum soundproof -
ness compatible with comfort as follows: Adjust the chin
strap and head ties until the ear cups (the large padded
cups which surround the entire ear) fit snugly against the
head and the earpieces are alined with the bore of the ear
canal. In this position the earpieces will surround the tragus
(fleshy part) of the ears but will not bend the tragus so
that it blocks the passage from the earpieces to the ear
canal. Screw the earpieces into the helmet until they rest
firmly but comfortably against the ears.
e. When the helmets are properly adjusted, the listeners
((24) and (25), fig. 4) will step onto the platform and plug
their respective tube ends into their earpieces. The sound
locator is now ready for operation.
Figure 6. — Corrector operator in action.
1. Multiplying pantograph.
2. Target air speed setting
knob.
7. Pantograph attaching stud
knob.
8. Parallax cam.
9. Declutching gear.
10. Target air speed scale.
11. Pantograph pointer.
12. Sight mirror cross lines.
13. Level.
14. Elevation clamp.
15. Parallax scale.
32
ANTIAIRCRAFT SEARCHLIGHT UNITS
55-56
Figure 7. — Acoustic corrector, sound locator, M2.
1. Pantograph. 4. Mirror.
2. Pantograph pointer. 5. Mirror cross lines.
3. Sight.
■ 56. Tracking the Target. — a. To aid the listeners to pick
up the target, the push button switch ((31), fig. 26) may be
pushed in, thereby decreasing the A. C. hum of the data
transmitters. As soon as the location of the target is clearly
established, release the switch. DO NOT track with this
switch pushed in.
b. The corrector operator will move the correction handle
and knob (34) in such a manner as to keep the image of the
pantograph pointer continuously on the cross lines of the
mirror.
33
56
COAST ARTILLERY FIELD MANUAL
c. The listeners will rotate their respective handwheels to
maintain a binaural balance on the sound source. The
handwheels are turned toward the ear in which the sound
predominates to achieve binaural balance.
CAUTION: In the operation of the sound locator the lis-
teners should be cautioned against making sudden changes
in the rotation of the handwheels. Such jerky operation
will cause the end of the pantograph to move back and forth
in the field of view of the corrector sight, thereby making it
impossible for the corrector operator to apply the proper
corrections to the transmitted data. The listeners should
be trained to track smoothly by getting into the habit of
rotating the handwheel continuously, even though they hear
the target intermittently. If the listener should detect that
he is lagging behind the target slightly he should accelerate
his handwheel rotation speed slowly until the target is again
centered. Likewise, he should retard his handwheel rotation
by a slight amount if he finds he is leading the target. Such
momentary deviations from true centering are not harmful
as they serve to sweep the beam over a small area in the
vicinity of the target, thereby assisting the search for the
target in a controlled manner. Jerky tracking is a far more
serious fault than slight inaccuracies in centering which are
gradually corrected.
d. The corrector operator must recognize that the panto-
graph pointer does not oscillate or move in jerky fashion
when the listeners follow the target perfectly. Therefore,
when jerky operation of the pointer occurs, he should realize
that it is due to the listeners and he will not attempt to follow
rapid movements of the pointer but will endeavor to average
out such irregularities, so that the correction he inserts will
be smooth and uniform.
e. It is emphasized here that the acoustic corrector opera-
tor should be trained to develop judgment in following the
pantograph pointer in his sight, rather than in the mere
mechanical performance of his work. By his delicate touch
he must smooth out the jerky variations introduced by the
trackers as they strive to keep the sound centered. In gen-
eral, the operator should endeavor to keep the pantograph
pointer within the circle inclosing the cross lines ( (12) , fig. 6) .
34
ANTIAIRCRAFT SEARCHLIGHT UNITS
57
■ 57. Operation of Sound Locator, M1A1. — a. This locator
(sometimes called the longhorn) has four metal horns
mounted on a four-wheel trailer. As shown in figure 8, four
exponential horns are mounted in trunnions that are
mounted on a turntable. One pair of horns (the upper and
lower) determines the elevation of the sound, the other pair
the azimuth. The pointing of these horns in azimuth and
elevation is transmitted mechanically to the acoustic cor-
rector which is mounted on one end of the trailer.
24
Figure 8. — Sound locator, M1A1
1. Acoustic corrector.
2. Jacks.
3. Front seat (removed).
4. Horns.
5. Traversing hand wheel.
6. Elevating handwheel.
7. Headset (azimuth).
8. Headset (elevation).
9. Horn journal bearings.
10. Azimuth scale.
11. Turntable.
12. Seats for operators.
13. Footrest.
14. Turntable locking screws.
15. Horn locking brace (removed) .
16. Traveling horn supports,
17. Hand clamp nuts.
18. Horn suppiort yoke.
19. Elevation shaft.
20. Rubber tubes.
21. Vertical columns.
22. Drawbar.
23. Side rails.
24. Covers for acoustic corrector.
25. Cable leading to comparator.
26. Brake handle.
35
57-58
COAST ARTILLERY FIELD MANUAL
b. When on the road, the locator is as shown in figure 28.
c. In operating the locator, the listeners are seated on op-
posite sides of the turntable and operate handwheels directly
in front of them. Listeners should be instructed to develop
judgment in their listening and centering. In following a
moving target, the handwheel should be kept moving at a
constant rate, even if the target is lost from time to time.
The cautions given in paragraph 56c also apply to the opera-
tion of this locator.
■ 58. Operation of Acoustic Corrector, Ml. — a. The esti-
mated altitude of the target as given toy the chief of section
is set in by turning the altitude setting knob ((1) , fig. 9) .
Figure 9. — Acoustic corrector, Ml.
1. Altitude scale and setting
knob.
2. Corrected azimuth scale and
releasing knob.
3. Corrected elevation scale and
releasing knob.
4. Differential gears.
6. Lamp.
7. Lamp switch.
8. Predicting mechanism and
scale, azimuth prediction.
9. Predicting mechanism and
scale, elevation prediction.
10.
11.
12.
13.
14.
15.
17.
18.
36
Plug receptacle.
Outer predictor scale pointers
and operating knobs.
Inner predictor scale pointers
and operating knobs and
clutch operating buttons.
Sound lag drum and chart.
Spotting correction knob,
azimuth.
Spotting correction knob,
elevation.
Data transmitter, azimuth.
Data transmitter, elevation.
ANTIAIRCRAFT SEARCHLIGHT UNITS
58
b. For this acoustic corrector two operators are required,
one of whom must be equipped with a stop watch. The
length of the interval during which a correction is to be
computed is indicated by the pointer at the sound lag drum
(13). The command is given: 1. ready, 2. TAKE, and
the watch is started. At the expiration of the indicated
time, the operator gives: 1. ready, 2. HALT.
c. Each operator insures that the prediction-scale pointer,
inner, is set at zero before a prediction operation is begun.
At the command take, the operators apply a slight pressure
with thumb or finger to the button (12) at the center of the
scale. At the command halt, the pressure is released. The
operator then brings up the outer-matching pointer (11) to
the position on the scale indicated by the inner pointer (12) .
This operation should be performed, as nearly as possible,
simultaneously with the movement of the inner pointer. As
soon as the pointers have been matched, the inner pointer
(12) is reset to zero and the operation is repeated.
d. The outer pointer (11) actuates the frame of the trans-
mitter and thus sends the corrected data to the comparator.
Therefore it should not be returned to zero, as a correction
once inserted should remain until another is determined and
introduced. Experience on the part of the operators will
indicate to them when an erroneous prediction has been
made, in which case the former one is left in the system
until the proper correction is determined by a subsequent
operation.
e. Atmospheric, wind, and arbitrary corrections can be
added to the readings at the transmitters by turning off the
amount of the correction on the spotting dials (14) and
(15). The black scales indicate an increase in azimuth or
elevation, while the red scales indicate a decrease.
/. To economize in time the acoustic corrector measures
the angular travel during only one-third of the actual pre-
dicted time. The sound-lag cylinder is graduated in terms
of one-third the actual sound-lag time, and appropriate
gearing places the correction for full sound-lag time in the
transmitter.
g. The corrector operators should understand enough of
the theory of the corrector to be able to use judgment in
37
58-60
COAST ARTILLERY FIELD MANUAL
determination and application of corrections. They should
know that the corrections determined will actually change
gradually, and that any radically different corrections should
not be applied to the corrector. The operators must "smooth
out" the corrections before applying them, insuring an even
flow of data to the control station. It is emphasized again
that the training of these operators must develop judgment
rather than a mere mechanical skill in the operation of the
instrument.
Section II
CONTROL STATION
■ 59. Function. — The control station is the device that
enables the searchlight to be controlled from a distance, and
to be directed at the point in the sky indicated by the sound
locator as the target's position. In addition, it enables the
searchlight to search the sky in the immediate vicinity of
the point indicated by the locator. This is accomplished by
manipulating the handwheels at the control station so as
to move the light up and down and right and left from the
indicated point.
■ 60. Mechanism. — The searching mechanisms on control
stations have undergone an evolution which has brought
them back to the place they started in the first units
equipped with distant electric control. At this time the
search was wholly manual, being accomplished by manipu-
lating the controls on the distant electric control system back-
ward and forward and up and down in order to obtain the
desired searching pattern in the sky. On the M1934 control
station a mechanically operated spiral searching device was
added. On the M1937 control station this was changed to
provide for an automatic electrical searching device in eleva-
tion only, the search in azimuth being accomplished man-
ually. On the M1939 unit all automatic searching devices
have been eliminated, and the search is accomplished man-
ually as on the MVI unit. All control stations having auto-
matic searching devices were provided with means for
throwing these automatic mechanisms out of gear and re-
38
ANTIAIRCRAFT SEARCHLIGHT UNITS
60-61
verting to manual operation. On the M1934 and all later
control stations, a pair of binoculars (or night glasses) was
provided to aid in the search. These glasses are auto-
matically directed on the point in the sky at which the
searchlight is pointed. With the aid of the glasses it has
proven possible to pick up targets which have been but
lightly flicked, or when they have been dimly illuminated by
the searchlight beam passing nearby in hunting the target.
On some types of aircraft it has been possible to make a
pick-up using the glasses alone as the glow of the exhaust
could be seen.
■ 61. Operation of Control Station, M1939. — a. On this
control station (fig. 10) there are three operators — an azi-
muth controller, an elevation controller, and the searchlight
commander (acting as control station chief) who looks
through the binoculars. The azimuth and elevation con-
trollers cause the searchlight to be set on the sound locator
data by centering the zero reader pointers at the control
station, and conduct the search by slowly and smoothly
manipulating the azimuth and elevation handwheels located
on the sides of the control station. As they search, the
searchlight commander observes that part of the sky through
his binoculars. If the sound locator is being properly oper-
ated it should place the beam within 5° of the target. The
searchers operate the controls to cover this 5° "area of
error." As soon as the target is picked up, the searchlight
commander takes over completely from the azimuth and
elevation controllers, keeping the light directly on the target
by movement of his handwheels. While tracking the illu-
minated target, the searchlight commander keeps it on the
side of the searchlight beam nearest the gun battery, so that
operators at the gun battery do not have to see the target
through the searchlight beam.
39
Figure 10. — <
83. Leveling jack.
103. Elevation observer's hand-
wheel.
106. Elevation handwheel
clutch adjuster.
112. Binocular mount clutch
adjuster.
114. Elevation zero search indi-
cator.
122. Azimuth observer's hand-
wheel.
124. Azimuth zero reader hand-
wheel.
125. Azimuth handwheel
clutch adjuster.
131. Binocular mount azimuth
slip adjuster.
132. Azimuth zero reader.
134. Search knob.
itrol station.
139. Signal buzzer push button.
141. Binocular mount adjuster
handles.
142. Carrying handles.
143. Binocular elevation zero
marker.
144. Binocular azimuth zero
marker.
147. Tripod.
156. Dial light switch.
160. Binocular mount counter.
219. Handhole cover plate.
220. Binocular height adjusting
knob.
315. Alinement lug.
342. D. E. C. switch.
417. Binocular mount.
418. Open sight.
419. Fifteen point receptacle.
ANTIAIRCRAFT SEARCHLIGHT UNITS
61
b. The three men composing the control station crew
should be trained together as a team, as the successful op-
eration of the station depends on an instinctive cooperation
among all three. The azimuth controller must keep the
zero reader needle on or in the vicinity of the zero point but
must also search in azimuth. If the target is not picked up
in a few seconds, the controller must insure that the light
be again pointed on sound locator data by seeing that his
zero reader needle is exactly zeroed. The elevation controller
handles his controls in a similar manner. At the command
flick, given as the light beam passes over the target, the
searchlight commander takes over complete charge of the
controls and keeps the light directed on the target.
c. The sequence of events at the control station on a
normal course occurs as follows:
(1) The sound locator operators will report on target, and
the moving of the zero reader needles will indicate that data
are coming through. This report will generally be given
when the target is about 10° to 20° above the horizontal in
elevation.
(2) The azimuth and elevation controllers center the zero
reader needles, thereby pointing the darkened searchlight
on sound locator data.
(3) At the command in action (generally given when
the target is about 30° to 45° above horizontal in elevation),
the searchlight is lighted, and the two controllers at the con-
trol station immediately commence their search.
(4) The target will next be momentarily illuminated
(flicked) by one of the lights in action. When this is noticed
by the chief of section or No. 4, they report flick to the
searchlight commander. When the searchlight commander
is ready to take over the operation of the control station
from the controllers, he commands: FLICK, takes over the
controls, and tracks the target.
(5) At the command out of action, the light is put out,
but all elements of the unit continue to track the target.
(6) At the command change target, the controllers center
the zero reader pointers, thereby pointing the light in the
41
61-63
COAST ARTILLERY FIELD MANUAL
direction indicated by the sound locator. Search is com-
menced for the new target in the usual manner.
Section III
SEARCHLIGHT
■ 62. Operator. — The searchlight operator must be trained
in the functioning of the searchlight itself. His post is at
the light during operation. Due to the number of auto-
matic devices provided, the searchlight operator has little
to do during normal operation. He should be thoroughly
familiar with the manual operation of all the automatic
devices and fully capable of operating them efficiently when
called upon.
■ 63. Normal Operation. — a. During normal operation, the
searchlight operator assists in unloading the light, setting it
up and leveling it, and connecting the cables.
b. He assists in orienting by pointing the light as directed
using the orienting sight. After the light and locator are
properly pointed, he centers the zero- reader meters by turn-
ing the knob on the azimuth and elevation receivers (for
details as to orienting the unit see pars. 97 and 99) .
c. At the command in action he closes the arc switch on
the light, thereby striking the arc. At out of action he
opens the arc switch.
d. After about 45 minutes of continuous operation (or
when the positive carbon is half used) the operator recar-
bons the light, replacing the eld carbons with a new positive
and new negative carbon at the first break in operation.
The new positive carbon should always have a crater previ-
ously formed by a few minutes of operation at the bivouac
or garage.
e. The operator constantly checks his ammeter and volt-
meter to see that the searchlight is operating on correct
current (145-150 amperes) and voltage (78 volts). He also
checks the appearance of the arc as seen in the ground glass
view finder, keeping the positive crater even with the ref-
erence line on the view finder.
42
ANTIAIRCRAFT SEARCHLIGHT UNITS 63-65
/. Adjustment of the arc length should only be undertaken
under the supervision of the chief of section, The length is
adjusted by turning the arc length adjusting screw shown
in the lower right corner of the lamp mechanism box ((27),
fig. 11) ; the greater the arc length, the greater the voltage
across the arc.
g. The thermostat control system should only be adjusted
under the supervision of one of the battery electrical ser-
geants or of the chief of section. Directions will be found
in the instruction book.
■ 64. Leveling the Light. — The light is first lifted off the
ground by means of its four leveling jacks ((83), fig. 21)
and approximately leveled. The light is traversed soi that
one level tube is parallel with the frame of the chassis; the
other will be at right angles to it. Using the leveling jacks,
the light is leveled so that the bubbles are centered in their
tubes. The light is then traversed 3,200 mils (180°). The
bubbles should remain centered; if they do not, bring them
halfway back to center using the jacks. Adjust the level
tubes themselves at the first opportunity, as they are out of
adjustment if the bubbles do not stay reasonably centered
during 6,400 mils (360°) of traverse. This adjustment
should only be performed under the supervision of the pla-
toon commander or one of the battery staff sergeants.
■ 65. Recarboning the Light. — a. To recarbon the light the
operator should enter the light on the side away from the
thermostat. He should wear gloves and should have on some
sort of clothing so that his arms, shoulders, or body will not
come in direct contact with hot metallic parts. The main
arc switch should be "off." If at night, the recarboning
light should be turned on.
b. Using the recarboning wrench, the operator forces apart
the jaws that grip the positive carbon, and the carbon stub
is withdrawn to the front. A new positive carbon ((15)
fig. 11) with a crater already formed by a few minutes of
operation is inserted from the front and the wrench is re-
moved, allowing the jaws to grip the carbon. (It is impera-
43
65-67
COAST ARTILLERY FIELD MANUAL
tive that the gear teeth mesh after the wrench is removed.)
When correctly placed, the positive carbon should project
% inch beyond the positive head.
Note. — In case a new carbon with no crater is used, it should
project i% 6 inch.
c. To recarbon the negative head, the operator pulls down
on the negative-release lever, thereby releasing the old nega-
tive carbon, which is removed. A new negative carbon (1) is
inserted so as to project 1 inch beyond the negative head,
and the negative-release lever is released allowing the neg-
ative mechanism to grip the carbon.
■ 66. Manual Operation. — a. Whenever an automatic device
fails, it is necessary to change to manual operation. The
operator should be drilled constantly on changing over to
manual operation so that he will be ready if a failure occurs.
b. (1) When the automatic positive feed (thermostat)
fails, it is possible to change to semiautomatic feed using
the semiautomatitc feed-rate adjusting knob ((6), fig. 11).
By moving the knob farther to the left it is possible to have
ttie motor feed the positive 1 carbon forward at a rate equal
to the rate of burning.
(2) Pull manual control may be exercised by turning the
positive hand feed (22) .
c. The negative feed, may be hand-controlled by shifting
the negative feed centralizer knob (12) from "auto" to
"hand" and turning the negative hand feed (11).
. d. The correct positions for the positive and negative car-
bons during manual control are checked by observing them
in the ground glass view finder and keeping each carbon
on its proper line.
■ 67. Manual Direction. — a. In case the distant electric con-
trol fails, it is possible to direct the searchlight manually,
either by moving the light itself or by means of the ex-
tended hand control.
b. By observing the zero reader dials, it is possible to
direct the light manually using sound locator data.
c. If no sound locator data are available, it is best to con-
nect the extended hand control and direct the light from the
end of its handle.
44
ANTIAIRCRAFT SEARCHLIGHT UNITS
Figure 11. — Lamp and lamp-control mechanism.
285203° — 40 i 45
68-70
COAST ARTILLERY FIELD MANUAL
Section IV
POWER PLANT
■ 68. Starting Power Plant. — The operation of starting is
practically the same as that of starting a car.
a. Put main switch ((20), fig. 12) and voltmeter and lamp
circuit breaker (19) in the "off'-' position.
b. Pull out choke control (9) and throttle control (11)
slightly.
c. Start the engine by turning on the ignition switch (16),
press in the starter button (12), and adjust choke (9), as
required for smooth operation. After the engine has
warmed up sufficiently and after operating smoothly a few
minutes, push choke (9) back in, and pull out throttle con-
trol to wide open position. Tachometer (6) should indicate
approximately 900 revolutions per minute.
■ 69. Listening Load Voltage Adjustment. — a. Close the
voltmeter and lamp circuit breaker ((19), fig. 12) and turn
the 115-volt light swith (14) to "on." This will light the
switchboard lamp, and the control panel voltmeter (4) will
indicate the no-load voltage, approximately 110 volts. The
tachometer (6) will indicate approximately 900 revolutions
per minute.
b. With the searchlight equipment properly connected,
throw the main switch (20) "on." The ammeter (3) should
indicate 10 to 15 amperes (listening load current) . Adjust
the listening load rheostat (2) so that the voltmeter reads
105 volts. No further adjustment of this rheostat should
normally be required except to compensate for temperature
variations.
■ 70. Arc Load Voltage Adjustment. — a. With the main
switch ((20), fig. 12) "on" and the arc load rheostat (1)
set at the middle of its travel, close the searchlight arc
switch.
b. Adjust the arc load rheostat so that voltmeter (4) indi-
cates 100 volts. With a cold unit it will be necessary to have
the voltage slightly lower in order to maintain the proper
46
ANTIAIRCRAFT SEARCHLIGHT UNITS
70
arc current. The instruments on the control panel (fig. 12)
should indicate approximately the following:
Ammeter (3) 165
Voltmeter (4) 100
Tachometer (6) 1,200
Oil gage (7) 15-20
Temperature gage (8) 160-200
Figure 12. — Control panel (front view) .
1. Arc load voltage rheostat.
2. Listening load voltage rheo-
stat.
3. Power ammeter.
4. Power voltmeter.
5. Charging ammeter.
6. Tachometer and revolution
counter.
7. Oil pressure gage.
8. Temperature gage.
9. Choke.
10. Gas gage.
11. Throttle.
12. Starter button.
13. 115-volt lamp receptacle.
14. 115-volt light switch.
15. Fan season switch.
16. Ignition switch.
17. 6-volt light switch.
18. 6-volt receptacle.
19. Power voltmeter and lamp
circuit breaker.
20. Main switch.
c. The power plant will adjust itself automatically while
changing from "listening load" to "arc load" or vice versa.
The engine automatically increases speed to 1,100 revolutions
per minute when the arc load is applied, and decreases to
875-900 revolutions per minute when the arc load is removed.
47
70-73
COAST ARTILLERY FIELD MANUAL
Arc load rheostat (1) when once set should not need to be
adjusted except to compensate for temperature variations.
■ 71. Manual Control. — a. The voltage and speed may be
controled manually should the governor fail or manual con-
trol be desired.
b. It is necessary to block the governor arm in forward
position in order to prevent interference from the mechanical
governor.
c. With throttle ((11), fig. 12) set at listening speed (900
r. p. m.) , the arc should be struck and at the same time the
throttle adjusted to obtain the correct arc load speed of
1,100 revolutions per minute. Satisfactory operation will be
obtained by maintaining settings as shown in paragraph 70.
WARNING: When changing from ard load to listening
load, quickly push in throttle control simultaneously with
removal of arc load to decrease engine speed to 900 revolu-
tions per minute. This must be done to avoid overspeeding
engine and excessively high voltage.
d. If the engine speed adjustments are carefully made, it
will be unnecessary to change settings of listening load
rheostat (2) or arc load rheostat (1) when changing from
one speed to another.
e. If any part of the governor on its control mechanism
fails, it is necessary to wire open the valve lever controlling
the butterfly valve in the valve box assembly. This will
allow the engine speed to be controlled by the throttle.
■ 72. Stopping Power Plant. — To stop the engine after the
arc load has been removed, open the main switch ((20), fig.
12) and turn the ignition switch (16) "off." Open the volt-
meter and lamp circuit breaker (19).
Note. — The main switch (20) should always be opened to avoid
starting a connected load.
Section V
VEHICLES
■ 73. Searchlight Vehicles. — Searchlight vehicles have
changed considerably. The first modern unit, the MVI, was
48
ANTIAIRCRAFT SEARCHLIGHT UNITS 73-74
carried by a combined truck-power plant (fig. 13) which
towed the sound locator trailer. The next unit, the M1934
(fig. 15) , had a similar arrangement employing a more power-
ful truck. These combined truck-power plants were called
power units. Subsequent units, the M1937 and M1939,
used two cargo trucks with each searchlight unit. The
M1940 unit employs two trucks of special design. (See figs.
16 and 17.)
H 74. MVI Power Unit (figs. 13 and 14) .—a. Description. —
Description of the automotive features will not be included
in this manual. A 15-kilowatt, 150-ampere, 100-volt, 1,800
revolutions per minute, compound generator is mounted on
the drive shaft of the motor with provision for engaging either
the generator for supplying the searchlight or the tail shaft
for locomotion. The generator clutch shifting lever is located
«m fv,^ ir»ff +v>g driver's seat. A Governor is provided to
maintain an engine speed of 1,800 revolutions per minute.
This governor may be disengaged when traveling by means
of the governor cut out control on the dash. A y 2 -kilowatt,
125-volt rotary converter, supplied by the main D. C. gen-
erator, furnishes the alternating current for the compara-
tor. It is located on the right running board. A control
panel is located in the driver's cab in rear of the seat. It
contains two main circuit breakers, D. C. ammeter and
voltmeter, generator field rheostat, rotary converter switch,
A. C. voltmeter, and illuminating lamp. The truck body
contains a loading winch with cable and ramps, boxes for
securing comparator, comparator and controller cables, and
two reels for the main power cables.
b. Operation. — (1) Traveling. — Before starting on the
road, check for the following conditions:
(a) Governor control should be out (governor disen-
gaged) .
(b) Generator clutch lever (left of driver) should be
locked forward by means of the chain provided.
(c) Generator ventilating doors should be clamped shut.
(d) The searchlight chassis should be locked in position
by the three clamping devices.
49
74
COAST ARTILLERY FIELD MANUAL
Figure 13. — MVI searchlight and power unit, traveling position
(paulin removed) .
1. Rotary converter.
2. D. C and A C. cable recepta-
cles.
3. Power cable reels.
4. Controller and comparator
cable storage boxes.
5. Controller and comparator
tripod.
6. Container for spare carbons.
7. Controller storage box.
8. Comparator storage box.
9. Loading winch axle.
(e) The azimuth lock of the searchlight must be locked
in its correct riding position.
(/) The steady bar should be locked in place.
(•60 The elevation clamp on the trunnion, the elevation
clutch, and the azimuth clutch should be released.
(h) The circuit breakers and switch on the control panel
should be open and the sliding doors closed.
(2) Unloading and connecting searchlight (fig. 14). — (a)
Release canvas cover and raise bows about 3 inches in their
sockets.
(b) Place ramps; secure with pins.
(c) Remove reel boxes and extended hand control.
(d) Release devices which secure searchlight to truck
body.
(e) Attach steering handle and loading winch cable.
50
ANTIAIRCRAFT SEARCHLIGHT UNITS
74
(/) Attach cable reel handles on each side of loading
winch, raise pawl from ratchet, and, with one man on each
crank and one man guiding the tongue, allow searchlight
to roll slowly down, the ramp.
(g) Unreel the main power cables and attach plugs to the
yellow receptacle on the power unit and searchlight, being
careful to see that the guides on the plugs are properly
fitted.
(ft) Interconnect all other cables between sound locator,
comparator, distant electric control, and searchlight accord-
ing to the color scheme of the plugs and receptacles.
(3) Generation of potior. — (a) Open ventilation ports of
generator and start engine.
(b) With engine idling, shift generator clutch lever (left
of driver) to the rear, engaging the generator to the drive
shaft. If gears will not mesh, it will be necessary to depress
the engine clutch, shift the transmission to low gear, and
gently release the engine clutch until the generator can be
engaged. The transmission should then be returned to the
neutral position.
(c) Engage governor; depress engine clutch and put gear
shift lever in high gear; release engine clutch carefully.
(<Z) Open throttle wide and advance the spark. (Speed-
ometer should read approximately 25 miles per hour.)
(e) Regulate field rheostat to bring direct current voltage
to 100 volts.
(/) When the engine has warmed up, close the circuit
breakers and start the rotary converter by closing the double
pole knife switch on the power panel.
(g) When the arc is struck, the following readings of the
meters should obtain:
Volts
Amperes
150
157
Searchlight operating alone
Searchlight and comparator
Searchlight, comparator, and con-
100
100
troller.
100
175
51
74-75
COAST ARTILLERY FIELD MANUAL
Figure 14. — MVI power unit (rear view), showing cables in place,
comparator in box, and method of stowing tripod.
1. Comparator box.
2. Loading light.
3. Main power cables.
i. Locking pins for searchlight.
5. Loading winch with cable
wound properly.
6. Coupling.
7. Carbon container.
8. Tripod.
9. Cable reel cranks in loaded
position.
10. Pins for locking rear seat.
11. Turnbuckle for locking
searchlight at) rear.
12. Ramps in position for load-
ing.
(h) After operating the arc for a time, it may be neces-
sary to raise the voltage above 100 volts to obtain the proper
arc current. This is due to the increase in resistance of the
cables as they become heated.
■ 75. M1934 Power Unit (fig. 15) . — This power unit is very
similar to the power unit MVI (par. 74) except that it has
a more powerful motor. It has a generator and switch-
board equipment designed to supply current for 150-ampere,
200-ampere, or 250-ampere operation of the searchlight.
The unit is designed to run at two engine speeds, a slow
(quiet) speed for the listening load and a 1,100 to 1,400
revolutions per minute operating speed. The unit automati-
52
ANTIAIRCRAFT SEARCHLIGHT UNITS 75-77
cally speeds up as the arc is struck and the heavier current
is needed.
PiGtTRE 15. — M1934 searchlight unit, showing power unit.
■ 76. M1937 and M1939 Vehicles. — a. These units were de-
signed to employ cargo trucks with a minimum of extra
equipment. Two trucks were required per unit; almost any
cargo truck of sufficient carrying capacity and large enough
body could be used.
b. A block and tackle was furnished for pulling light and
power plant into the truck; ramps for each truck allowed
the light and power plant to be drawn up into the truck
body; some form of hold-down device kept the equipment
from shifting when the truck was in motion. The crew
rode where they could in the truck cabs and bodies.
■ 77. M1940 Vehicle (fig. 16).— The vehicles furnished
with the M1940 units are special vehicles. They are of the
cab-over-engine type and drive through four rear wheels.
The special double cabs (fig. 17) accommodate the entire
crew of the searchlight unit.
53
77
COAST ARTILLERY FIELD MANUAL
Figure 16. — Truck, M1940 searchlight.
Figure 17. — Cab, M1940 searchlight truck.
54
CHAPTER 4
PREPARATIONS FOR ACTION AND FOR MOVEMENT
■ 78. Scope. — This section describes the setting up of the
equipment from traveling position on the road to operating
position ready for action.
■ 79. Traveling Position. — a. When on the road, one com-
plete searchlight unit uses two trucks — the first carrying
the searchlight, control station, and the sound locator; and
the second truck the power plant and the cables.
b. The personnel and equipment are in places on the
trucks as indicated in figure 18.
■ 80. Selection of Searchlight Position. — The position se-
lected should be —
a. On or near a road good enough to permit use by the
trucks in all kinds of weather. (In terrain permitting
trucks to move cross country in all kinds of weather, this
provision may be disregarded.)
b. Fairly open, so that light and locator can operate down
to an elevation of +10°.
c. Away from main highways, railways, factories, and
other sources of noise.
d. On level ground or on an elevation rather than in a
depression, so that sound waves will not be distorted by
surrounding hills before reaching the locator.
e. At least a mile from the nearest antiaircraft gun bat-
tery, to avoid drawing enemy fire to the gun battery.
Paragraphs
Section I. Preparing for action
II. Orienting and synchronizing.
III. Preparing for the road
IV. Protective measures
78- 94
95- 99
100-108
109-111
Section I
PREPARING FOR ACTION
55
81-82 COAST ARTILLERY FIELD MANUAL
■ 81. Going Into Position. — On arrival at the searchlight
position, the chief of section indicates the location of the
power plant, searchlight, control station, and sound locator,
and gives the necessary instructions to have the materiel
prepared for action.
■ 82. Actions of Truck No. 1 at Prepare for Action. — a.
At the command prepare for action, truck No. 1 proceeds
to the indicated searchlight position where the searchlight
is released from its hold-down devices, unloaded, set up.
and leveled.
TRUCK NO. I
PERSONNEL
TRUCK NO. 2
Figure 18. — Loading of trucks Nos. 1 and 2, modern searchlight
unit.
56
ANTIAIRCRAFT SEARCHLIGHT UNITS 82-84
b. The truck then moves to the control station position
where the control station is unloaded and set up.
c. From the control station the truck proceeds to the
sound locator position, where the sound locator parts are
unfastened from their hold-down devices, unloaded, as-
sembled, and the locator is leveled.
d. After the unloading and assembling of the sound lo-
cator are completed, the truck is driven to the concealed
parking area previously designated by the chief of section.
There the chauffeur assures himself that the truck is hidden
from ground and air observation.
■ 83. Actions of Truck No. 2 at Prepare for Action. — a. At
the command prepare for action, truck. No. 2 proceeds to
the power plant position. The power plant is unloaded and
prepared for action.
b. The truck is then driven slowly from the power plant
position to the searchlight position, laying the two power
(yellow) cables as it goes.
c. From the searchlight position the truck proceeds slowly
to the control station and sound locator positions, laying the
control station (red) and the sound locator (blue) cables as
it goes.
d. After all cables are laid, the truck is driven to the con-
cealed parking area previously designated by the chief of
section. There the chauffeur assures himself that the truck
is hidden from ground and air observation.
■ 84. Normal Set-Up for Later Model Searchlight
Units. — a. The normal set-up for the later model units
(M1937 and later) is shown in figure 19 (i).
b. This set-up is employed by all units equipped with zero
readers (M1937 and later). The control station may be
located anywhere within the length of the red cable from
the searchlight (500 feet on the M1939 unit) , and the locator
may be placed anywhere within the length of the blue cable
from the searchlight (900 feet on the M1939 unit) . Usually,
however, the sound locator is set up on the opposite side of
the searchlight from the power plant in order to have the
maximum possible distance between the two.
57
84-85
COAST ARTILLERY FIELD MANUAL
c. The ideal set-up is afforded when a litotle-used road,
pointing in the direction of the target's expected approach,
is available. In this situation the equipment is located as
shown in figure 19 ©. The equipment should be set up well
to the side of the road and the cables thrown completely off
the road, if practicable.
■ 85. Normal Set-up for Older Model Searchlight Units. —
a. The older model units (M1934 and earlier) employ the
comparator instead of the zero reader as a means of pointing
the searchlight on sound locator data. A normal set-up for
these units is shown in figure 19 ®. It should be noted that
the 200-foot white cable is not furnished with the M1934
unit but only on earlier models.
b. In these units, the power plant, light, control station,
and locator are generally set up in a straight line. In con-
trast with the later units, where locator and control station
are each connected to the searchlight, the locator is con-
nected by cable with the control station, and the control
station with the light. As may be seen from figure 19 ®
the cables afford a maximum separation of locator and
power plant of 1,000 feet.
c. As with the later models, the ideal arrangement is pos-
sible when a little-used road is available. The unit is set up
in the formation shown in figure 19 ©.
POWER PLANT SEARCHLIGHT SOUND LOCATOR
CONTROL
STATION
® M1939 unit.
58
85
COAST ARTILLERY FIELD MANUAL
Figure 20. — M1939 60-inch antiaircraft searchlight (front view) .
15. Positive carbon.
267.
Lamp.
34. Bear drum.
306.
Azimuth clutch lever.
39. Sliding panel.
356.
Front door glass.
41. Elevation daylight sights.
357.
Recarboning lamp.
44. Front drum.
358.
Azimuth scale lamp.
50. Junction box.
360.
Steering tongue lug.
56. Azimuth motor.
361.
Ventilating fan exhaust
58. Transportation bar.
vent.
65. Ballast resistor.
362.
Ventilating fan Intake vents.
264. Arc view peep sight.
364.
Elevation data receiver
265. Ground glass finder.
housing.
266. Handhole plate.
60
ANTIAIRCRAFT SEARCHLIGHT UNITS
85
Figure 21. — M1939 60-inch antiaircraft searchlight (rear view).
35. Lamp control mechanism
box.
36. Elevation scale lamp.
37. Elevation scale.
38. Recarboning lamp switch.
40. Azimuth daylight sights.
45. Elevation gear sector.
47. Hand controller socket.
49. Elevation motor.
53. Arc switch box.
54. Extension lamp receptacle.
55. Scale and meter light
switch.
59. Transportation lock bar
lug.
61. Power cable receptacles.
63. Controller cable receptacle.
64. Sound locator cable recep^
tacle.
65. Ballast resistor.
66. Ventilating motor housing.
67. Azimuth data receiver
housing.
69. Signal buzzer.
70. Meter box.
76. Azimuth lock.
83. Leveling jack.
264. Arc view peep sight.
270. Orienting sights.
324. Dynamotor pilot light.
328. Dynamotor behind wheel.
359. Azimuth scale.
235203°
61
Figure 22. — Control station wi'
83. Leveling jacks.
103. Elevation observer's hand-
wheel.
105. Elevation zero reader hand-
wheel.
121. Zero search knob.
122. Azimuth observer's hand-
wheel.
131. Azimuth slip clutch (bi-
nocular adjuster).
binocular mount folded down.
133. Elevation zero reader.
149. Spirit levels.
155. Clamp knob.
219. Handwheel cover plate.
220. Binocular height adjusting
knob.
342. D. C. switch.
417. Binocular mount.
419. Cable receptacle.
ANTIAIRCRAFT SEARCHLIGHT UNITS
85-86
Figure 23. — Placing main assembly and correction unit of sound
locator, M2, on pedestal.
16. Main assembly.
17. Cable plug.
18. Pedestal.
19. Platform.
20. Transportation bracket.
29. Azimuth handwheel clamp
knob.
■ 86. Setting Up Searchlight. — a. At the command pre-
pare for action, the first truck drives up to the location
indicated for the searchlight. The ramps are placed in
position, the four hold-down turnbuckles are released, the
block and tackle placed, and the searchlight is lowered
down the ramp. The hook on the end of the block and
tackle rope should be hooked securely to the light. It is
important that the crew stand clear, so that in the event
the light breaks away no one will be injured.
b. The transportation lock is unpinned, the transporta-
tion bar ((58), fig. 20) lowered to its horizontal position,
and the searchlight is depressed to the horizontal. Since
the searchlight is transported with the elevation clutch on
"hand" position and with the elevation clamp free, the drum
may readily be lowered to zero elevation.
63
86-87
COAST ARTILLERY FIELD MANUAL
c. Remove the azimuth pin and note that the searchlight
revolves freely. CAUTION: Do not replace the pin for
locking the searchlight in its transporting position at this
time, as the pin will foul the lock when the searchlight is
rotated.
d. The light is then leveled by means of the four leveling
jacks until the level bubble stays centered while the light
is traversed 360° as described in paragraph 64.
■ 87. Setting Up Control Station. — a. The first truck then
proceeds to the location chosen for the control station.
&. The control station is arranged to be transported in
three parts — the binocular mount, the control unit, and the
tripod. (Pigs. 10 and 22.) Assemble these three parts for
operation as described below:
(1) The tripod should be set in place within 500 feet of
the searchlight and its protective cap removed.
(2) The control unit is properly positioned with respect
to the tripod turntable by means of a slot in its skirt which
Figure 24. — Attaching azimuth horn of sound locator, M2, to
main assembly.
16. Main assembly. 21. Azimuth horn.
64
ANTIAIRCRAFT SEARCHLIGHT UNITS
87
fits a lug on the tripod. Make sure that the lug is in aline-
ment with the slot when performing the next step.
(3) Lift the control unit to a position over the tripod and
lower it slowly in a plane parallel with the top of the tripod.
Take care not to strike the control station on the contact
plate of the tripod.
(4) A pinion located under the skirt of the control unit
must mesh with the external tripod gear as the control unit
is lowered to its seat. This pinion drives its shaft through
a friction coupling to allow the control box to be swung
in azimuth without disengaging the pinion or turning the
azimuth handwheels.
(5) When the control unit is seated, take up on the clamp
knobs so that they apply equal pressure. These clamp
Figure 25. — Attaching elevation and common horn unit of sound
locator, M2, to main assembly.
21. Azimuth horn. 22. Common horn (azimuth and elevation) .
Note. — Some horn covers are closed with clips (figure shows
zippers) .
65
87-88
COAST ARTILLERY FIELD MANUAL
knobs are located on opposite sides of the skirt of the control
unit.
(6) Remove the binocular mount from its box.
(7) Remove the cover plate and insert the column in its
place on top of the control unit turning it slightly in azimuth
to be sure the coupling on the bottom engages.
(8) Attach the column to the control unit by means of
the four screws provided.
(9) Open the binocular mount to its operating position,
making sure that its locking pin is inserted from the proper
side so as to hold it in place.
(10) Place the binoculars (night glasses) in position at
the top of the binocular mount.
(11) Adjust the leveling jacks so that the control station
can make a complete traverse without apparent displace-
ment of the level bubbles.
■ 88. Setting Up Sound Locator, M2. — a. After unloading
the control station, the truck moves to the location indicated
for the sound locator.
b. The complete sound locator is broken down into six
component parts for transportation. These parts, with their
approximate weights, are listed below:
Pounds
Two-horn assembly . 90
Single-horn, assembly 55
Main assembly and corrector (with carry-
ing case and spare parts) total— 310
Pedestal '. 30
Platform 140
Cable and reel 350
c. The crew unloads the equipment and assembles the
sound locator as follows:
(1) Carry the platform to the sound locator position, set
it up, and level it approximately. Place the platform so
that the footing is firm for the leveling jacks.
(2) Place the pedestal on the platform and bolt it down.
(See fig. 23.)
(3) Place the main assembly and corrector on the ped-
estal, the cable connections (17) being first dropped down
66
ANTIAIRCRAFT SEARCHLIGHT UNITS
88
Figuee 26. — Sound locator, M2 (including corrector) .
30. Portable lamp receptacle. 34. Sight correction handle and
31. Self synchronous push but- knob.
ton switch. 35. Azimuth scale.
33. Elevation handwheel. 36. Elevation scale.
67
88 COAST ARTILLERY FIELD MANUAL
y To OP 3
\
\
Figure 27. — Arrangement of stakes around sound locator.
through the pedestal (18), as shown in figure 23. Bolt this
unit in place. Remove the transportation bracket (20) , then
loosen elevation friction clamp ((14), fig. 6), turn to maxi-
mum elevation, and set up the elevation clamp tightly.
Markers on the base of the main assembly show the location
of the dowel pins.
68
ANTIAIRCRAFT SEARCHLIGHT UNITS
88
(4) Bolt the horn assemblies in place as shown in fig-
ures 24 and 25, assembling the single horn (21) first. The
horns are more easily handled if the canvas covers are not
removed until after they are assembled in place. Markers
on the hubs of the horn arms show the location of the holes
for the dowel pins.
(5) Mount the pantograph on the corrector case as shown
in figure 6; secure the pantograph in place by means of knob
(7).
(6) Connect the receptacle end of the blue cable to the
plug underneath the sound locator platform (fig. 26), and
then clamp this joint to the under side of the platform.
Connect the plug end of the cable to the blue receptacle on
the searchlight.
(7) Adjust the leveling jacks until the level ((13), fig. 6)
indicates that the platform is horizontal. The bubble
should remain centered while the locator is rotated 360°.
All four jack pads must bear firmly against the ground.
Check this condition by walking around on the platform to
detect any tendency to rock. The locator is now ready for
orienting.
Figure 28. — Sound locator, M1A1, in traveling position.
69
88
COAST ARTILLERY FIELD MANUAL
■S 0) ME
<MUQ
70
ANTIAIRCRAFT SEARCHLIGHT UNITS
88
Figure 30. — Left side
A. Air cleaner.
B. Carburetor.
C. Oil filter.
D. Ignition coil.
E. Engine.
F. Distributor.
G. Solenoid.
H. Water pump.
I. Arc load voltage rheostat.
J. Power ammeter.
of power plant (doors open) .
K. Listening load voltage rheo-
stat.
L. Power voltmeter.
M. Throttle.
N. Main switch.
O. Power generator.
P. Gas tank.
Q. Power cable receptacles.
R. License mounting holes.
d. After the locator has been completely set up, a stake
should be driven in the ground in the direction of each
advanced listening post and of each of the other four lights
of the platoon. The arrangement of stakes, shown in
figure 27, enables the chief of section to point the locator
in accordance with information received by phone from
these points.
71
89-91
COAST ARTILLERY FIELD MANUAL
■ 89. Setting Up Sound Locator, M1A1. — With the locator
in traveling position (fig. 28) , to go into operating position —
a. Remove the horns from the traveling position supports
by releasing the hom locking brace and pins. Then clamp
the horns into place on the horn support, which is in a
position corresponding to 90° elevation, by means of the
double hooks and horn clamping screws. Be sure that the
numbers on the horns and supports correspond.
b. Unlock the turntable by loosening the three locking
screws, and level by means of the four jacks suspended
from the chassis of the trailer. Two levels are provided on
the turntable for leveling purposes.
■ 90. Unloading Power Plant. — a. When using M1937 and
later equipment, the second truck drives to the location in-
dicated for the power plant. The ramps are placed in
position, the block and tackle hooked up, the hold-down
devices disconnected, and the power plant (figs. 29 and 30)
unloaded. It is important that personnel be cautioned to
stand clear of the power plant while on the ramp, in case
the block and tackle should fail.
b. The power plant is always placed in operating posi-
tion with the gasoline motor end away from the rest of the
unit, in order to decrease the amount of sound reaching the
locator, light, and control station.
■ 91. Preparing Power Plant for Operation. — a. After the
power plant is unloaded, the operator should first check to
see that it has sufficient —
(1) Water in the radiator.
(2) Oil in the crankcase. The oil should never be allowed
to fall below the halfway mark on the dip stick. In summer
use SAE 30 and in winter (if temperature falls below 30° F.)
use SAE 10. The capacity of the crankcase is 7 quarts.
(3) Gasoline in the tank.
b. Both radiator doors should be fastened open. For quick
warming up of plant in cold weather, doors may be kept
closed until desired motor temperature is reached.
c. Fasten the switchboard door open with the chain. This
door must be open to insure proper cooling, as the cooling
72
ANTIAIRCRAFT SEARCHLIGHT UNITS
91-92
fan draws its air through this opening. Leave the other
hood side doors closed.
■ 92. Cables. — a. (1) Multi-conductor cables connect the
power plant, light, control station, and sound locator. For
identification the plugs of these cables are painted different
colors as follows:
(a) Yellow — two single-conductor main power cables con-
necting light and power plant. These carry the power for
the searchlight, the distant electric control system, and the
rotary converter.
(b) Red — a 15-conductor cable connecting the control
station with the light. It transmits the distant electric con-
trol impulses from the control station to the elevation and
azimuth training motors on the light. It transmits the zero
reader data from the light to the control station. It also
connects a push button on the control station with a buzzer
on the searchlight.
(c) Blue — a 10-cpnductor cable connecting the sound lo-
cator and the searchlight. It transmits the azimuth and
elevation as determined by the locator and acoustic correc-
tor to the searchlight.
(2) On the earlier model searchlight units (M1934 and
earlier) , cables have the same general function as described
in (a) , (b) , and (c) above. On the MVI unit, an additional
cable with white plugs connects control station and light.
For details see TM 4-210.
b. These cables are carried on reels and are transported
in truck No. 2, the power plant truck. The reels are
equipped with small wheels so that they may be pushed
around like longshoremen's hand trucks. However, they are
not suitable for cable laying for long distances except on
paved roads.
c. Where it is practicable, cable is laid from the body of
the truck. Where impracticable, the cable is laid by placing
the reel on. the ground near the searchlight, and pulling
the cable off the reel and to the piece of equipment. Where
the cable is very long or must go around curves, it is neces-
sary to place additional men along the cable to keep it from
binding or becoming snagged.
73
93-94
COAST ARTILLERY FIELD MANUAL
■ 93. Catjtions in Handling Cables. — a. As about 90 per-
cent of searchlight materiel failures are caused by cable
difficulties, it is imperative that cables be handled with great
care. Most cable failures take place within a foot of the
plugs, which indicates that rough handling of the cable at
the plug is a major source of difficulty. It has been found
by actual experience that the observance of the rules given
in b below greatly reduces cable failures.
b. (1) Plugs should be removed from sockets by pulling
on the plug, not on the cable. Pulling on the cable will bend
and break the delicate electrical conductors at the plug.
(2) When, moving the cables, pull on the cable, not on
the plug. Pulling on the plug will rupture the delicate
electrical conductors.
(3) When moving the cables, do not allow the plugs to
drag along the ground, catching on rocks, bushes, and other
obstructions. Carry the cable so the plug is clear of the
ground.
(4) Do not lay the cable so that it is likely to be run over
by vehicles.
(5) Do not kink the cables.
(6) Do not operate the searchlight with the main power
cable (the one with yellow plugs) on the cable reels. In-
sufficient ventilation may cause the cables to overheat and
destroy the rubber insulation.
(7) Do not be in too much of a hurry to reel up the
cables when march order is given. A few minutes saved
the night before may cause hours of repair work the next
day.
(8) Do not put cable plugs into sockets until cables are
completely laid and off the cable reels.
■ 94. Laying Cables. — a. Cables are carried on truck No. 2,
the power plant truck. While on the road, the cable reels
are fastened to the truck body by the hold-down devices.
When ready to lay a cable, it is first necessary to unfasten
the reel from its hold-down device and move it to the rear
of the truck.
b. The two power (yellow) cables are laid first. Truck
No. 2 goes to the power plant position. After unloading the
74
ANTIAIRCRAFT SEARCHLIGHT UNITS
94-96
plant, the yellow cable reel is moved to the rear of the
truck. Both yellow cables are laid at the same time as the
truck moves slowly from the power plant to the light. Do
not put cable plugs in sockets on power plant until cable
is completely laid and off the truck.
c. Both the control station (red) cable and the sound
locator (blue) cable are laid at the same time. Both reels
are moved to the rear of the truck when it is at the search-
light. The plugs are passed to a man on the ground who
holds them, and the cables are unreeled as the truck moves
slowly ahead to the control station, where the red cable
ends. The truck then moves on to the sound locator, com-
pleting the laying of the blue cable. During the laying op-
eration there should be at least one man for each reel on
the truck and a man on the ground to guide the cable or
cables as they are unreeled.
d. At the power plant, light, control station, and locator,
the cable plugs are connected to their proper sockets. These
sockets are painted the same color as the plugs to facilitate
identification. The plugs should not be connected until the
cables are completely laid and off the reels.
Section II
ORIENTING AND SYNCHRONIZING
■ 95. Scope. — This section describes methods of orienting
and synchronizing the various elements of the searchlight
unit.
■ 96. General. — The searchlight and sound locator must be
oriented and synchronized in azimuth and elevation. Orien-
tation may be accomplished using true azimuth or an arbi-
trary zero. In the description following, an arbitrary zero is
used. It is assumed that the searchlight and sound locator
have been set up and proper electrical connections made.
Before commencing the operations listed below, if the control
station is equipped with a searching mechanism make sure
that the searching control is at zero position as directed
in the manufacturer's instructions supplied with that
equipment.
75
97
COAST ARTILLERY FIELD MANUAL
■ 97. Orienting in Azimuth on Distant Point. — a. The
easiest method of orientation is by the use of a celestial
body (moon, sun, or star) or a distant object. In this
method, sound locator, searchlight, and control station are
pointed at the celestial body or distant object by means of
their sights. While so pointed, the azimuth scales on the
searchlight and sound locator are given the same reading
(generally zero). The power is turned on and the azi-
muth zero readers adjusted to read zero as described in
(3) below.
b. The details of the operation follow:
(1) Searchlight. — (a) Disengage the azimuth clutch knob
by pulling the azimuth clutch handle in the direction indi-
cated as "out."
(b) Turn the searchlight in azimuth until it points at the
celestial body (or distant point), sighting by means of the
orienting sight on the searchlight ((270), fig. 21).
(c) Re-engage the azimuth clutch by pushing the clutch
lever in the direction indicated as "in."
(d) Start the power plant and turn the red D. C. switch
at the control station "on."
(e) Recheck the searchlight azimuth position, using the
distant electric control to obtain a vernier adjustment.
(/) Set the searchlight azimuth scale to zero. To do this,
loosen the azimuth scale located at the base of the search-
light and turn it until zero on the scale is under the pointer
index. Tighten the screw.
(2) Sound locator, M2. — (a) Set the target speed to zero
by means of knob ((2) fig. 6).
(b) Set the parallax scale (15) to zero.
(c) Loosen the azimuth handwheel clamp knob ((29), fig.
23) , and point the sound locator at the celestial body (or dis-
tant point) . To do this, use the corrector sight and get the
images of the pantograph pointer and the celestial body
(or distant point) to coincide on the cross lines of the mirror.
Ee careful not to disturb the correction handle thereafter
until the control station is oriented in azimuth.
(<Z) Take up on the azimuth clamp to hold the sound
locator in this position.
76
ANTIAIRCRAFT SEARCHLIGHT UNITS 97-98
(e) Set the sound locator azimuth scale to zero. (Slip
scale around.)
(/) Push down declutching gear ((9), fig. 6) and rotate
the parallax cam (8) until the arrow on top of the cam
points directly at the celestial body (or distant point) . Then
remesh the gearing.
(?) With the power on, the azimuth zero readers are ad-
justed to read zero as described in (3) below.
(3) Data receiver adjustment. — (a) When the searchlight
and sound locator have been oriented as described in (1) and
(2) above, the azimuth zero readers on the searchlight and
control station may or may not show a zero reading. They
should be made to read zero by removing the cover on the
azimuth data receiver at the base of the searchlight and
turning the adjustment knob.
(b) It is possible to get two zero readings on the azimuth
zero reader meters 180° apart. The correct zero reading is
obtained when the needle of the azimuth zero reader at the
control station moves to the "right" when the zero reader
handwheel is rotated clockwise and to the "left" when the
handwheel is rotated counterclockwise.
(4) Control station. — Hold the azimuth handwheels from
turning and slip the control station until it is directed at the
celestial body (or distant object) . This is accomplished by
sighting through the binoculars.
c. When searchlight, sound locator, and control station
are all pointed at the same celestial body (or distant point) ;
the azimuth scales of light and locator read the same; and
the zero reader meters read zero; the unit is in orientation,
has been synchronized, and is ready for action.
■ 98. Orienting in Azimuth When Distant Point Is Not
Available. — When a distant point is not available, the unit
is oriented on itself as described below:
a. Searchlight. — (1) Disengage the azimuth clutch knob
by pulling the azimuth clutch handle in the direction indi-
cated as "out."
(2) Turn the searchlight in azimuth until it points at
the pedestal of the sound locator, sighting by means of
the orienting sights on the searchlight.
235203°— 40 6
77
98
COAST ARTILLERY FIELD MANUAL
(3) Re-engage the azimuth clutch by pushing the clutch
lever in the direction indicated as "in."
(4) Start the power plant and turn the red D. C. switch
at the control station to "on."
(5) Recheck the searchlight azimuth position, using the
distant electric control to obtain a vernier adjustment.
(6) Set the searchlight azimuth scale to 3,200 mils. To
do this, loosen the azimuth scale located at the base of the
searchlight and turn it until 3,200 on the scale is under the
pointer index. Tighten the screw and, using the distant
electric control, swing the searchlight in azimuth to the
zero position. In this way the distant electric control sys-
tem is used to lock (electrically) the searchlight in the zero
position in which it has just been set.
b. Sound locator, M2. — (1) Set the target speed to zero
by means of knob ((2), fig. 6).
(2) Set the parallax scale (15) to zero.
(3) Loosen the azimuth handwheel clamp knob ((29),
fig. 23) and point the sound locator at the searchlight. To
do this, use the corrector sight and get the images of the
pantograph pointer and the rear drum of the searchlight
to coincide on the cross lines of the mirror. Be careful
not to disturb the correction handle thereafter until the
control unit is oriented and synchronized in azimuth.
(4) Take up on the azimuth clamp to hold the sound
locator in this position.
(5) Set the sound locator azimuth scale to zero. (Slip
scale around.)
(6) Push down declutching gear ((9), fig. 6) and rotate
the parallax cam (8) until the arrow on top of the cam
points directly at the searchlight. Then remesh the gearing.
(7) With the light and locator oriented as described
above, and the power on, the azimuth zero readers are ad-
justed to read zero as described in paragraph 97.
c. Control station. — (1) After completing the orientation
of searchlight and sound locator, direct the searchlight at
the control station using the distant electric control. Sight
the searchlight exactly on the control station using the
light's orienting sight.
78
ANTIAIRCRAFT SEARCHLIGHT UNITS
98-99
(2) Hold the azimuth handwheels from turning and slip
the control station until it is backsighted on the searchlight.
This is accomplished by sighting backward through the
open sight on the binoculars.
(3) The control station is now oriented, that is, pointed
in the same direction as the searchlight. Movements of
the azimuth handwheels will move both control station and
searchlight the same amount and direction.
■ 99. Orienting and Synchronizing in Elevation. — o.
Searchlight. — (1) Turn the searchlight elevation control
clutch lever to hand position and set the searchlight to zero
elevation by hand.
(2) Then lock (electrically) the searchlight in the zero
elevation position by turning the clutch lever to the distant
electric control position. Do not force the clutch lever; if
it will not move easily into distant electric control position,
keep a slight pressure on the lever and slowly rock the
searchlight a few mils in elevation until it does.
b. Sound locator, M2. — Lock the sound locator at zero
elevation by means of lock ((14), fig. 6). With zero speed
and parallax settings, center the pantograph pointer on the
cross lines of the mirror. Be careful not to disturb the
correction handle thereafter when orienting and synchro-
nizing.
c. Control station. — The binocular mount on the control
station should be set at zero elevation. However, check to
see that the binocular elevation zero marker ((143), fig. 10)
is on the zero mark, thereby indicating zero elevation.
d. Data receiver adjustment. — (1) When the search-
light and sound locator have been oriented as described
above, the elevation zero readers on the searchlight and
control station may or may not show a zero reading. They
should be made to read zero by turning the housing of the
elevation data receiver located on the left trunnion arm of
the searchlight.
Note. — The elevation receiver will usually not require adjust-
ment, but it is advisable to check it for correctness ol setting at
this time.
(2) It is possible to get two zero readings on the elevation
zero reader meters 180° apart. The correct zero reading is
79
99-103
COAST ARTILLERY' FIELD MANUAL
obtained when the needle of the elevation zero reader at the
control station moves to the right when the zero reader
handwheel is rotated clockwise and to the left when the
handwheel is rotated counterclockwise.
Section III
PREPARING FOR THE ROAD
■ 100. Scope. — This section describes the disassembling and
loading of the equipment preparatory to a move by road.
Some of the duties require modification when loading sound
locator, M1A1.
■ 101. Operating Position. — When the command march
order is given, the light unit is in operating position with the
crew distributed as shown in figure 33. The two trucks are
in the parking area hidden from observation.
■ 102. Actions of Truck No. l at March Order. — a. At the
command march order, truck No. 1 leaves its parking area
and goes to the sound locator position. The sound locator
is disassembled and loaded on the truck, and the parts fas-
tened in their proper places by the hold-down devices.
b. The truck then proceeds to the control station position,
where the control station is disassembled, loaded on the
truck, and fastened in place by the hold-down devices.
c. The truck leaves the control station position and pro-
ceeds to the searchlight position. The searchlight is placed
in traveling position, loaded on the truck, and fastened in
$its place by means of the four hold-down turnbuckles
provided.
d. Truck No. 1 then proceeds to its designated position on
the road and awaits further orders.
■ 103. Actions of Truck No. 2 at March Order. — a. At the
command march order, truck No. 2 leaves its parking area
and proceeds to the control station position where it picks
up two men and then proceeds to the sound locator position.
Starting at the sound locator, the truck proceeds slowly
(backing up) toward the control station, picking up the
sound locator (blue) cable as it moves. From the control
80
ANTIAIRCRAFT SEARCHLIGHT UNITS 103-105
station the truck continues moving slowly (backing up) to
the searchlight position, picking up both the red and the blue
cables en route.
b. Starting from the searchlight the truck slowly backs
up toward the power plant position, picking up the power
(yellow) cables as it moves.
c. When all cables have been reeled in and the reels fas-
tened in place by the hold-down devices, the ramps are
placed in position for loading the power plant, and the power
plant is pulled up into the truck body by means of the
block and tackle. The plant is fastened in place by means
of the hold-down devices.
d. Truck No. 2 proceeds to its designated position on the
road and takes place behind truck No. 1.
e. When ready to move off, the equipment and personnel
should be loaded in the two trucks as shown in figure 18.
■ 104. Loading Sound Locator. — o. At the command march
order, the blue cable is disconnected from the short cable
attached to the locator.
b. The pantograph is removed from the locator and placed
in its carrying box.
c. The horns are elevated to approximately 90° and the
canvas covers replaced. The double horn and then the sin-
gle horn are removed.
d. The main assembly is unbolted, removed from the pedes-
tal, and placed in its box.
e. The pedestal is unbolted from the platform and de-
tached from it.
/. The five parts are placed on the forward end of truck
No. 1 in their proper places and secured in position by means
of the hold-down devices.
■ 105. Loading Control Station. — a. At the command
march order, the red cable is disconnected, and the bino-
culars are removed from the mount and placed in their
carrying case.
b. The binocular mount is removed from the control unit
and replaced in its carrying box.
c. The control unit is lifted from the tripod.
d. The tripod is collapsed.
81
105-108
COAST ARTILLERY FIELD MANUAL
e. The subdivisions of the control station are then loaded
in their proper places on truck No. 1 and secured by means
of the hold-down devices.
■ 106. Loading Searchlight. — a. At the command march
order, the blue, red, and yellow cables are disconnected;
the leveling jacks are run up; the light is traversed to the
proper position and the azimuth pin replaced; the search-
light is elevated to approximately 90", and the transportation
lock pinned in place.
b. The ramps are placed in position and the light drawn
up into the body of truck No. 1 by means of the block and
tackle.
c. The light is then secured in position by means of the
hold-down devices.
d. The extended hand control and the ramps are replaced
in position on the truck.
■ 107. Loading Cables. — a. At the command march order,
truck No. 2 proceeds to the sound locator. Here the blue
and red cable reels are moved to the rear of the truck.
As the truck backs up from the locator to the control
station, the blue cable is reeled in. As it backs up from the
control station to the searchlight, both blue and red cables
are reeled in. When completely reeled in, the blue and red
cable reels are moved to their traveling positions in the
truck and secured by means of the hold-down devices.
b. The yellow cable reel is next brought to the rear of the
truck. As the truck backs up from light to power plant, the
two yellow cables are reeled in. When completely reeled in,
the yellow reel is moved to its traveling position on the truck
and secured by means of the hold-down devices.
■ 108. Loading Power Plant. — a. At the command march
order, the switchboard and radiator doors are lowered and
fastened.
b. The ramps are placed in position, and the power plant
is drawn up into the body of truck No. 2 by means of the
block and tackle. All personnel should stand clear of the
power plant while it is being loaded in order to avoid injury
in case the plant breaks loose while going up the ramp.
82
ANTIAIRCRAFT SEARCHLIGHT UNITS 108-111
e. The power plant is secured in position in the body of
truck No. 2 by means of the hold-down devices.
Section IV
PROTECTIVE MEASURES
■ 109. Camouflage. — a. Camouflage is employed to prevent
enemy air or ground (principally air) observers from locat-
ing materiel and personnel or from realizing their presence.
b. Camouflage discipline is necessary to prevent disclosing
the location of materiel or personnel by the paths made by
men or vehicles as they move around. (See FM 5-20.)
■ 110. Protection of Materiel and Crew. — a. When search-
light units are operating in one location for a time, it is
desirable to protect materiel and crew by means of earth-
works and trenches.
b. Personnel should be protected by providing slit trenches
(2 feet wide and 6 feet deep) at the locator, control station,
light, and power plant. The crew takes refuge in these
trenches whenever, during a bombardment, it is not neces-
sary to operate the unit.
c. Materiel is protected by sandbagging when practicable
or by partially sinking the equipment in the ground. (See
FM 5-15.)
■ 111. Gas Defense. — a. Searchlight materiel and personnel
may be gassed by means of shell, bombs, or spray from the
air. When gas is placed on the unit at the time of an
aerial attack, it will ordinarily be possible to illuminate the
targets for the duration of the attack. As soon as the aerial
attack is over, the unit should be moved to another ungassed
position nearby.
b. After personnel has been under a persistent gas (mus-
tard) attack it is necessary to decontaminate (clean) their
clothing, and it is important that the men be required to
bathe.
c. Materiel should be kept covered as much as possible
when under gas. A canvas cover will prevent drops of
liquid gas from coming in contact with the materiel. Bright
83
Ill
COAST ARTILLERY FIELD MANUAL
surfaces should be especially protected. A light coating of
grease should be given bright surfaces.
d. After a gas attack, materiel must be decontaminated
before using, both to avoid corrosion of the materiel and
injury to the using personnel. This is generally accom-
plished by the use of solutions or pastes of certain chem-
icals. For details on decontamination see *FM 3-5.
*See Appendix.
84
CHAPTER 5
ORGANIZATION
Section I. Searchlight battery.
II. Searchlight platoon.
III. Searchlight section.
Paragraphs
.__ 112-113
— 114r-115
— 116-117
Section I
SEARCHLIGHT BATTERY
■ 112. Composition. — a. The antiaircraft searchlight battery
(T/O 4-18 and T/O 4-118) consists of a battery headquar-
ters section, a maintenance section, and three searchlight
platoons. The searchlight platoons are the tactical units of
the searchlight defense.
b. The battery headquarters section contains the person-
nel necessary for battery administration.
c. The maintenance section contains the personnel re-
quired for battery messing, supply, and transportation, and
for the operation of the repair facilities.
■ 113. Battery Commander. — a. The battery commander is
responsible for the efficiency, training, administration, and
supply of the battery and for the condition of the materiel
assigned to it.
(1) He supervises the maintenance, technical operation,
and supply of searchlight and sound locator equipment.
(2) Under the battalion commander, he is responsible for
the illumination of all aerial targets operating within effec-
tive range of the lights.
b. He selects and coordinates the general locations for the
lights. The selection of the exact locations for the lights is
made by the platoon commanders concerned.
Section II
SEARCHLIGHT PLATOON
■ 114. Composition. — a. The antiaircraft searchlight pla-
toon is composed of a platoon headquarters and five search-
light sections.
85
114-116
COAST ARTILLERY FIELD MANUAL
b. The platoon headquarters contains the platoon com-
mander and the personnel necessary to furnish technical
advice and assistance to the searchlight sections on the
operation, maintenance, and repair of searchlight materiel;
personnel to establish and operate the platoon wire com-
munication net; and chauffeurs for platoon headquarters
vehicles.
■ 115. Formation. — The searchlight platoon assembles with
the platoon headquarters on the right, the searchlight sec-
tions in numerical order on the left at 4-pace intervals.
The platoon commander takes post 6 paces in front of the
center of the platoon (fig. 31) .
PLAT.
-4
NO. 1
_4^
NO. 2
-4 —
NO. 3
-4 —
NO. 4
~4 —
PACES
N0.5
HQ.
PACES
SECTION
PACES
SECTION
PACES
SECTION
PACES
SECTION
SECTION
□
a
a
a
CHIEFS OF
SECTION
PACES
PLATOON COMMANDER
Figure 31. — Formation of antiaircraft searchlight platoon.
Section III
SEARCHLIGHT SECTION
■ 116. Composition. — The searchlight section consists of a
sound locator squad and a searchlight squad, and comprises
the personnel necessary to man one complete searchlight
unit — sound locator, control station, searchlight, power
plant, and vehicles. The mobile section at war strength is
organized as follows:
a. The chief of section.
b. The sound locator squad consisting of the chief of
section, acting as chief of the sound locator squad, and
Nos. —
1. Listener, azimuth.
2. Listener, elevation.
3. Operator, acoustic corrector.
4. Operator, telephone.
86
ANTIAIRCRAFT SEARCHLIGHT UNITS 116-117
c. The searchlight squad consisting of the searchlight
commander, acting as control station chief, and Nos. —
5. Controller, azimuth (operator, control station) .
6. Controller, elevation (operator, control station).
7. Operator, searchlight.
8. Operator, power plant.
9. Chauffeur, truck No. 1.
10. Chauffeur, truck No. 2.
Note. — The mobile searchlight section at peace strength and
the semimobile searchlight section at peace and war strengths
are discussed in paragraphs 141 to 143, inclusive.
■ 117. Formation. — a. Each section assembles in two ranks
with 4 inches between files and 40 inches between ranks.
Within each squad, men form in numerical order with odd
numbers in the rear rank and even numbers in the front
rank (fig. 32). The post of the searchlight commander is
in the front rank, uncovered and 4 inches to the right of
No. 6. The post of the chief of section is in the front
rank 1 pace to the right of No. 2.
b. When setting up, operating, and loading the equip-
ment, the men normally move at ease and in such forma-
tion as permits the most efficient handling of the equip-
ment! The posts of the crew in operating position are
shown in figure 33.
87
117
COAST ARTILLERY' FIELD MANUAL
to
I?
88
ANTIAIRCRAFT SEARCHLIGHT UNITS
CHAPTER 6
SERVICE OP THE PIECE
Paragraphs
Section I. Searchlight platoon action
II. Duties of personnel
III. Drill of searchlight section
IV. Notes on the service of the piece.
118-126
127-129
130-143
144-151
Section I
SEARCHLIGHT PLATOON ACTION
■ 118. Control of Searchlight Action. — Control of search-
light action may be retained by the platoon commander or
decentralized to the chiefs of section. It is normally de-
centralized.
■ 119. Decentralized Control. — When control is decentral-
ized, the responsibility for the selection, pick-up, and carry
of targets belongs to the chiefs of section. In this case the
chiefs of section each act independently in selecting, track-
ing, and illuminating targets.
■ 120. Selection of Targets. — The platoon commander,
chief of section, and searchlight commanders should be
thoroughly familiar with types and formations of aircraft
and their identification by sound characteristics. In each
situation the platoon commanders and the chiefs of section
should know the mission of the antiaircraft defense and the
general location of all adjacent elements involved.
■ 121. Warning Command. — On receiving information of the
presence or approach of a possible target from a listening
post, a chief of section, or higher echelons, the platoon com-
mander sends to all sections the command stand by.
■ 122. Tracking. — a. Centralised control. — As soon as the
target has come within tracking range, it will be assigned
to all sections and they will be ordered to commence track-
ing. The assignment of target will include, when known,
90
ANTIAIRCRAFT SEARCHLIGHT UNITS 122-126
the locality over which the target is flying, number and
type of aircraft, direction of flight, and estimated altitude.
For example, a complete assignment of target command
would be target; biglerville; formation bombers; flying
NORTH, HIGH.
b. Decentralized control. — As soon as ine target has come
within tracking range, each chief of section assigns the tar-
get to his section.
■ 123. Light Action. — a. (1) Centralised control. — As soon as
the target is within range of one or more lights that have
been reported "Ready," the platoon commander puts such
lights as he may elect in action by the command nos.
m action, or all lights in action.
(2) Decentralized control. — As soon as the chief of section
of the pick-up light nearest the target estimates that the
favorable moment for commencing the search has arrived,
he commands: IN ACTION. Other pick-up lights in range
immediately go into action.
b. While friendly aircraft, and in some situations certain
types of hostile aircraft, should not be illuminated, the com-
mander should not wait for positive identification by sound
to go into action. If at any time after the searchlights go
into action the target is identified, either by sound, visually,
or by telephone, as one that should not be illuminated, all
lights are put out of action.
■ 124. Following the Target. — After the target is picked
up, two carry lights follow the target until it is shot down
or flies out of range, or until other carry lights located in
the direction of flight have commenced to follow it.
■ 125. Searching With Other Lights. — When the lights
from an adjacent platoon go into action, the platoon com-
mander commands: STAND BY.
■ 126. Coordination of Defense. — When the platoon is a
part of a larger unit, the commander of the larger unit will
issue such orders involving the functioning of the platoon
as are necessary to make it a part of a coordinated defense.
91
127-128 COAST ARTILLERY FIELD*MANUAL
Section II
DUTIES OF PERSONNEL
■ 127. Platoon Commander. — a. The platoon commander is
responsible for the technical training and efficiency of the
personnel and for the condition of the materiel assigned to
his platoon.
b. He is sometimes responsible for the tactical handling
of the platoon. This involves the choice of which target to
Illuminate, how many lights to use for searching and how
many for carrying, when to change targets, and when to
decentralize control to the chiefs of section.
c. The platoon commander normally selects the positions
for the individual lights and the advanced listening (obser-
vation) posts (fig. 3).
d. He specifies the communication net that will be laid.
e. For details as to tactical handling, selection of posi-
tions, and communication nets, see FM 4^105.
■ 128. Chief of Section. — a. The chief of section (a ser-
geant) is in command of one searchlight unit and is respon-
sible for the efficiency of the personnel and the condition
of the materiel under his charge.
b. The chief of section will ordinarily select targets and
determine the proper time for illuminating them. It is im-
portant that he assure himself that the locator listeners are
definitely tracking the target before giving in action. In
case of failure of telephone communications, he will always
go into action on his own initiative. If the command sec-
tion leader's action has been given or if telephone com-
munication has failed, the chief of section will assume the
responsibility of selection and illumination of targets. In
such cases he will be guided by the same considerations as
the platoon commander.
c. He normally selects the exact locations for the sound
locator, control station, searchlight, and power plant (either
alone or in conference with platoon commander) .
d. He supervises the service of the piece, including going
into and out of position. He gives the commands prepare
FOR ACTION, EXAMINE EQUIPMENT, TRACK, and IN ACTION.
92
ANTIAIRCRAFT SEARCHLIGHT UNITS
128-131
e. He personally directs the work of care and preserva-
tion of equipment assigned to the unit.
/. He acts as sound locator chief, in addition to his duties
as chief of section.
g. He directs the orienting and synchronizing of the
searchlight unit.
h. He selects the parking place of the trucks, and after
all equipment is unloaded he orders the chauffeur to park
them at this designated place.
■ 129. Searchlight Commander. — a. The searchlight com-
mander (a corporal) commands the searchlight squad. He
is responsible for the efficiency of the control station crew,
the searchlight operator, and the power plant operator;
and for the condition of the control station, searchlight,
and power plant.
b. Acting as control station chief, he supervises the search
for the target, and carries the target after it is picked up.
c. He is responsible for orienting and synchronizing the
searchlight and control station with the sound locator.
■ 130. Scope. — This section outlines a drill for an antiair-
craft searchlight section, mobile, at war strength. Modifica-
tions made necessary by the smaller numbers of men pro-
vided in semimobile units and units at peace strength are
described in paragraphs 141 to 143, inclusive.
■ 131. Prepare for Action. — a. As the vehicles of the sec-
tion reach the vicinity of the searchlight position, the chief
of section commands: PREPARE FOR ACTION, and indicates
the locations for the sound locator, control station, search-
light, power plant, and the parking area for the vehicles. No.
9 drives truck No. 1 to the searchlight position, where Nos. 1,
2, 5, and 9 assist No. 7 in unloading, setting up, and leveling
the light (par. 86) . No. 7 remains at the light, connects up
the yellow, blue, and red cable plugs to the light, removes
the extended hand control and places it near the light, and
prepares the searchlight for action.
235203°— 40 7 93
Section m
DRILL OP SEARCHLIGHT SECTION
131
COAST ARTILLERY FIELD MANUAL
b. Truck No. 1 is driven to the control station position
where Nos. 1, 2, and 5 unload and set up the control station
(par. 87) . No. 5 removes the automatic rifle from the truck
and places it near the control station. No. 5 remains with
the control station, levels it, connects up the red cable, and
prepares the station for action.
•c. Truck No. 1 is then driven to the sound locator posi-
tion where Nos. 1, 2, and 9 unload and set up the sound
locator (par. 88). No. 1 connects the blue cable to the
locator. No. 3 removes the pantograph from its case and
connects it in place on the locator. Nos. 1 and 2 level the
locator. Under the supervision of the chief of section,
No. 2 drives stakes indicating the direction of the advanced
listening posts and the other lights (fig. 27).
d. No. 9 then drives the truck to a position on the road
near the searchlight and awaits orders.
e. No. 4 leaves truck No. 2 at the searchlight position and
proceeds to the telephone connection (end of wire line),
connects his telephone, calls the platoon command post,
and if communication thereto is satisfactory, reports "Com-
munication in order" to his chief of section. If communi-
cation cannot be established with the platoon command
post, he reports that fact to the chief of section immedi-
ately.
/. No. 10 drives truck No. 2 to the indicated power plant
position. No. 8 removes the automatic rifle from the truck
and places it in a location convenient to the power plant
operating position. Under the supervision of the search-
light commander, Nos. 3, 6, 8, and 10 unload the power
plant and place it in its operating position. No. 8 remains
at the power plant, connects the yellow cables, and prepares
the plant for action (pars. 90 and 91).
«r. Nos. 3 and 6 move the yellow cable reel to the rear end
of the truck (No. 2) and pay out the two yellow cables as
the truck is slowly driven from the power plant to the
searchlight position. When the cable has been unreeled, its
reel is replaced by Nos. 3 and 6 in its traveling position in
the truck.
h. At the searchlight position, Nos. 3 and 6 move the red
and blue cable reels to the rear of the truck. No. 3 pays
94
ANTIAIRCRAFT SEARCHLIGHT UNITS 131-132
out the blue cable and the searchlight commander the red
cable as the truck slowly moves from the searchlight to the
control station. No. 6 walks along in the rear of the truck,
guiding the cables as they come off the reels, and directing
them to the side of the road. No. 6 remains at the control
station and assists in preparing it for action.
i. The searchlight commander pays out the blue cable as
the truck slowly moves from the control station to the
sound locator position. No. 3 walks along in rear of the
truck directing the cable to the side of the road. After the
blue cable is laid, No. 3 returns the cable reel to its traveling
position in the truck, dismounts, and remains at the locator.
j. The searchlight commander returns to his post at the
control station, and No. 10 drives the truck to a position on
the road near the searchlight and awaits orders.
■ 132. Examine Equipment. — a. The chief of section com-
mands: EXAMINE EQUIPMENT, as soon as all items of
equipment are in their proper positions and all cables are
connected. At this command, he verifies the proper func-
tioning of all equipment and supervises the orientation and
synchronization of the complete unit.
b. Nos. 1 and 2 examine the locator, verify its level, and
the functioning of the elevating and traversing apparatus.
After their examination is completed, they orient the locator
as described in detail in paragraphs 96 to 99, inclusive.
No. 3 examines the acoustic corrector, sets in the parallax
correction, and assists Nos. 1 and 2 in orienting the locator.
Nos. 1 and 2 then examine their helmets for proper fit and
adjustment.
c. No. 4 tests communication with the platoon command
post and with the advanced listening post to his front (if
any). If communications are not functioning properly, he
reports the fact to the chief of section.
d. The searchlight commander inspects the power plant,
searchlight, and control station, paying special attention to
the latter. He supervises the orientation of the light with
the locator and the control station with the light as de-
scribed in paragraphs 96 to 99, inclusive. He supervises the
synchronizing of the elevation and azimuth zero reader sys-
95
132
COAST ARTILLERY FIELD MANUAL
terns, making sure that movements of the control station
handwheels cause the zero reader needles to move in the
proper direction.
e. Nos. 5 and 6 examine the control station. They test
the functioning of the distant electric control by elevating
and traversing the light from the control station. They
assist in orienting the control station with the light as
described in paragraphs 97 and 98. No. 5 examines the
automatic rifle to see that it is in operating condition. He
is responsible that a proper supply of ammunition is on hand.
/. No. 7 (searchlight operator) examines the searchlight
and sees that all plugs are properly connected to sockets;
that the searchlight is leveled and properly connected for
distant electric control; that spare positive and negative
carbons are on hand; and that new or nearly new carbons
are in place in the lamp mechanism. If the tactical situa-
tion permits, he strikes the arc, and observes the voltmeter,
ammeter, and ground glass finder to see that the arc is
functioning normally. He extinguishes the arc as soon as
possible. He examines the extended hand control. Under
the supervision of the searchlight commander, he orients
the light with the locator as described in paragraphs 96 to
99, inclusive, synchronizes the zero reader system by adjust-
ing the azimuths and elevation receivers on the light, and
orients the light with the control station.
g. No. 8 (power-plant operator) examines the power plant,
sees that the gasoline, oil, and water supply is correct, and
that the yellow cable plugs are properly connected (par. 94) .
He starts the motor and builds up the voltage to the required
no-load value (110 volts) . (See pars. 68 to 71, incl.) With
the searchlight unit equipment all connected, he closes the
main switch ( (20) , fig. 12) . The instruments should now indi-
cate the proper listening load values (105 volts and 10-15
amperes) . If the arc is struck, he notes that the instruments
indicate the proper arc load values (100 volts and 160-165
amperes). He examines the automatic rifle to see that it
is in operating condition. He is responsible that a proper
supply of ammunition is on hand.
h. Nos. 9 and 10 drive the trucks to the parking places
designated by the chief of section. There they insure that
96
ANTIAIRCRAFT SEARCHLIGHT UNITS 132-133
the trucks are hidden from ground and air observation.
They inspect their trucks, seeing that the supply of gasoline,
oil, and water is correct, and that the trucks are in proper
operating condition.
i. When all equipment is in order, the chief of section
directs No. 4 to report "No. in order" to the platoon
command post.
■ 133. Rest. — a. When no action is imminent, or when or-
dered by the platoon commander, the chief of section com-
mands: REST. The command is repeated by the searchlight
commander. For rest periods, the chief of section arranges
the men in reliefs for the various necessary posts, as follows:
(1) Listener at or near locator.
(2) Telephone operator.
(3) Power-plant operator at or near power plant.
b. The chief of section will divide the hours of darkness
with the searchlight commander, so that one or the other
is definitely in command at all times.
c. Nos. 1, 2, and 3 take turns as listeners at or near the
locator. They search the sky for enemy aircraft, and if
any are seen or heard they immediately report to the chief
of section. They also look for the beams of nearby search-
lights.
d. Nos. 4, 5, and 6 take turns as telephone operator. No.
5 carries the automatic rifle to the telephone position.
Whoever is on duty as telephone operator mans the rifle
during an attack.
e. No. 8 opens the switches on the power plant and turns
off the motor. Nos. 7 and 8 take turns as power plant
operators. Whoever is on duty at the time of an attack
mans the automatic rifle.
/. Nos. 9 and 10 fill duties as assigned by the chief of
section. They may be used as vehicle guards at the trucks
or as reliefs for other men of the section.
g. Those members of the unit crew not on duty remain
in the vicinity of the equipment they man in order to be
able to go into action with a minimum of delay.
97
134
COAST ARTILLERY FIELD MANUAL
■ 134. Stand By. — o. stand by is given by the chief of sec-
tion when a target is detected, an adjacent searchlight goes
into action, or when orders are received from the platoon
command post. The command is generally followed by a
target designation. The chief of section sees that all men
are alerted and at their posts and supervises preparations
to go into action. He directs the locator crew in the di-
rection of the target's approach, as received from the ad-
vanced listeners or the platoon command post. He gives
to the acoustic corrector operator the estimated air speed
of the target. He reports to the platoon command post
"No. on target" when the target has been definitely
located by the locator listeners.
b. The searchlight commander repeats the command
stand by. When power is on all lines, and power plant,
searchlight, and control station are ready for action, he
reports "Light standing by" to the chief of section. When
the locator is definitely following the target, he causes the
elevation and azimuth controllers to direct the darkened
searchlight by means of the distant electric control.
c. Nos. 1 and 2 take post at the locator and put on their
helmets. No. 2 presses the button decreasing the hum of
the data transmitters. They move their locator horns as
directed by the chief of section so as to pick up the sound
of the target. When the target has been definitely located,
No. 1 reports "On target" to the chief of section. No. 3
sets the estimated air speed of the target into the acoustic
corrector.
d. No. 4 repeats the command and stays at the telephone
ready for further messages.
e. Nos. 5 and 6 stand at their posts at the control station.
As soon as the zero reader pointers move consistently, in-
dicating that the locator is tracking the target, they center
the zero reader pointers by moving their handwheels the
necessary amount and direction.
/. No. 7 takes post at the searchlight and awaits orders.
He checks the voltmeter reading. If it is not at approxi-
mately 100 volts, he notifies the power plant operator.
g. No. 8 starts the power plant motor; builds up the volt-
age to the proper no-load value (110 volts) ; closes the
98
ANTIAIRCRAFT SEARCHLIGHT UNITS 134-138
switches; and when the instruments read 105 volts and
10-15 amperes at listening load, he reports "Power plant
ready" to the searchlight commander.
h. Nos. 9 and 10 perform duties assigned by the chief of
section.
■ 135. Track. — a. The command track is given by the chief
of section when the locator crew reports "On target." When
the chief of section estimates that the most favorable mo-
ment for going into action has arrived, he reports to the
platoon command post "No. ready."
b. The searchlight commander repeats the command and
causes the azimuth and elevation controllers to point the
darkened light by continuously centering the zero readers.
c. Nos. 1 and 2 track the target, centering the sound by
turning their handwheels. No. 1 gives the chief of section
such details as to the number and types of planes and their
direction of flight as he may determine from time to time.
This information is forwarded to platoon headquarters only
on request. No. 2 releases the button on the locator so that
the data transmitters will operate at full voltage. No. 3
operates the acoustic corrector so as to keep the pantograph
pointer centered on the cross wires in the mirror.
d. No. 4 stands by at the telephone for further messages.
e. Nos. 5 and 6 continuously center the zero readers by
turning the azimuth and elevation handwheels on the con-
trol station.
/. No. 7 stands by at the searchlight ready to strike the
arc. He observes his instruments, noting that the voltage
is at the proper value.
fir. No. 8 keeps the power plant operating on listening load,
checking his instruments to see that the voltage and cur-
rent remain at the proper value. Nos. 9 and 10 perform
any duties assigned by the chief of section.
■ 136. In Action. — a. The command in action is given by
the chief of section (or received over the phone from the
platoon command post). The chief of section continues to
supervise the operation of the sound locator and acoustic
corrector; looks for the target, and reports illumination or
99
136
COAST ARTILLERY FIELD MANUAL
flicks (very brief illuminations of the target) to the search-
light commander.
b. The searchlight commander repeats the command in
action and causes Nos. 5 and 6 to commence an immediate
search for the target, using their respective handwheels.
He observes the light beam through the binoculars, being
especially watchful for flicks. He calls "Data" whenever he
wishes Nos. 5 and 6 to center the zero readers exactly.
When the target is flicked, he commands: FLICK, takes over
personal operation of the control station from the control-
lers, and carries the target until it is out of range or until
directed otherwise. If he receives the command in action
before the sound locator has found the target, he causes the
controllers to search at the intersection of the beams of the
other lights until the locator picks up the target.
c. Nos. 1 and 2 continue to track the target. No. 3 con-
tinues to operate the acoustic corrector by centering the
pantograph pointer! on the cross lines on the mirror.
Note. — After target is illuminated, pantograph pointer, cross
lines and target should be alined. The amount the target is off
this line is a measurement of the inaccuracy of the locator
corrector system.
d. No. 4 stands by at the telephone. He watches the sky,
reporting all flicks and illuminations to the searchlight
commander.
e. Nos. 5 and 6 search by moving their zero reader point-
ers first to one side and then to the other of the zero posi-
tion, centering exactly when the searchlight commander
calls "Data." When the airplane is illuminated, they with-
draw from the control station so as to avoid interference
with the control of the beam.
/. No. 7 closes the main arc switch. He keeps watch on
his instruments, seeing that the arc operates at 78 volts
and 145-150 amperes. He recarbons the arc (par. 65) at
the first break in operations after the positive carbon is
about half consumed (after about 45 minutes of operation) .
sr. No. 8 continues to operate the power plant, checking
to insure that the current and voltage are at the proper
full-load value (160-165 amperes and 100 volts).
100
ANTIAIRCRAFT SEARCHLIGHT UNITS 136-138
h. Nos. 9 and 10 perform any duties assigned by the chief
of section.
■ 137. Out of Action. — a. The command out of action is
given by the chief of section (or received from the platoon
command post).
b. The searchlight commander repeats the command and
causes the control station crew to continue centering the
zero reader pointers.
c. Nos. 1 and 2 continue to track the target. No. 3 con-
tinues to operate the corrector. No. 4 stands by at the
telephone. Nos. 5 and 6 continue to center the zero readers.
d. No. 7 opens the main arc switch, extinguishing the arc,
stands by the light, ready to close the arc switch on com-
mand, and observes the voltmeter to see that proper listen-
ing load voltage is maintained (100 volts). He recarbons
if necessary. No. 8 continues to operate the power plant,
checking to see that the proper voltage (105 volts) and cur-
rent (10-15 amperes) for the listening load are maintained.
e. Nos. 9 and 10 perform duties assigned by the chief of
section.
B 138. Change Target. — a The command change target, fol-
lowed by the designation of the new target, will be given
by the chief of section (or received from the platoon com-
mand post). The chief of section directs the locator crew
to point the locator at the new target. If the target is
not already illuminated, he causes the personnel to search
for and pick up the new target in the usual manner.
b. The searchlight commander repeats the command. He
causes the control station crew to center their zero readers,
thereby pointing the light in the direction of the new
target.
c. Nos. 1 and 2 cease tracking the old target and point the
locator in the direction of the new target as directed by the
chief of section. If the target is not already illuminated,
they search for, pick up, and track the target (by sound)
in the usual manner. No. 3 operates the acoustic corrector
in the usual manner as soon as the listeners pick up the
target. No. 4 stands by at the telephone.
101
138-139 COAST ARTILLERY FIELD MANUAL
d. Nos. 5 and 6, at the direction of the searchlight com-
mander, center their zero readers, thereby pointing the light
at the new target. During search, pick-up, and carry they
operate in the usual manner.
e. Nos. 7 and 8 stand by for further orders.
/. Nos. 9 and 10 perform duties as assigned by the chief
of section.
■ 139. March Order. — a. When it is desired to prepare the
light unit for movement on the road, the chief of section
commands: MARCH ORDER. The command is repeated
by the searchlight commander.
b. At this command No. 9 drives truck No. 1 to the locator
position. No. 3 removes the pantograph and places it in its
carrying box. Nos. 1, 2, 4, and 9 disassemble the locator,
load it on the truck, and fasten it in its traveling position
(par. 104).
e. Truck No. 1 next proceeds to the control-station posi-
tion. Nos. 1, 2, 4, and 5 disassemble the control station,
load it on the truck, and fasten it in its traveling position
(par. 105).
d. Truck No. 1 then moves to the searchlight position.
Here Nos. 1, 2, 4, 5, 7, and 9 prepare the light for traveling,
load it on the truck, and fasten it in traveling position by
means of the hold-down devices provided (par. 106) .
e. The chief of section posts No. 5 as automatic rifleman
in the forward end of the truck body overlooking the cab.
The chief of section and Nos. 1, 2, 7, and 9 enter the cab, and
the truck is moved to its designated place on the road.
Note. — The automatic rifleman is relieved from time to time by
other men on truck No. 1.
f. When truck No. 1 starts for the locator position, truck
No. 2 is moved to the control station position by No. 10,
where he picks up the searchlight commander and No. 6,
and then proceeds to the locator position. At the locator
position, the blue and red cable reels are moved to the rear
of the truck. The blue cable is reeled in by No. 3 as the
truck slowly backs to the control station. No. 6 walks along
ahead of the truck, freeing the cable from any entangle-
ments, and insuring that it is fed evenly to No. 3 on the
102
ANTIAIRCRAFT SEARCHLIGHT UNITS 139-141
truck. At the control station the red cable is started on its
reel, and it is reeled in by No. 6 as the truck slowly backs
to the light. No. 3 continues to reel in the blue cable. The
searchlight commander walks along ahead of the truck,
freeing both cables, and insuring that they are evenly fed to
the reels on the truck. On arrival at the searchlight, both
red and blue cable reels are replaced in their traveling posi-
tions on the truck, and fastened in place by means of the
hold-down devices.
g. At the searchlight position the yellow cable reel is
moved to the rear of the truck. Nos. 3 and 6 reel in the
yellow cables, assisted by the searchlight commander on the
ground, as truck No. 2 slowly backs from the light to the
power plant position. On arrival at the power plant, the
full yellow reel is replaced in traveling position on the truck
and fastened with the hold-down device.
h. At the power plant, Nos. 3 and 6 are joined by No. 4.
No. 8 (the power plant operator) places the power plant in
traveling condition (par. 108). Nos. 3, 4, 6, 8, and 10,
supervised by the searchlight commander, load the power
plant into the truck body, and fasten it in place by means
of the hold-down devices.
i. The searchlight commander posts No. 8 as automatic
rifleman in the rear of the truck body. The searchlight
commander and Nos. 3, 4, 6, and 10 enter the cab, and the
truck takes its place on the road behind truck No. 1, ready
to move.
Note. — The automatic rifleman is relieved from time to time by
other men on truck No. 2.
■ 140. Drill for Searchlight Section, Mobile, War
Strength. — The drill for the searchlight section as given in
this chapter and in chapter 8 is for a section (12 enlisted
men) of a mobile searchlight battery at war strength.
(T/O 4-18.)
■ 141. Drill for Searchlight Section, Mobile, Peace-
Strength. — Under the peace-strength organization only 11
men are authorized for a mobile unit. At this strength, one
chauffeur (No. 10) is eliminated. The duties of No. 10 are
assigned to No. 8 (power-plant operator) . In this organiza-
103
141-144 COAST ARTILLERY FIELD MANUAL
tion, truck No. 2 is driven by No. 8 and is parked near the
power-plant position. At examine equipment, No. 8 devotes
all his attention to the power plant, and No. 9 checks both
trucks. (T/O 4-18.)
■ 142. Drill for Searchlight Section, Semimobile, War
Strength. — Under the war-strength organization only 10
men are authorized for a semimobile unit. At this strength
both chauffeurs (Nos. 9 and 10) are eliminated. The duties
of No. 9 are taken over by No. 7 (searchlight operator), and
the duties of No. 10 by No. 8 (power-plant operator). As
semimobile units are not designed to move rapidly and fre-
quently, this adjustment can be made without great loss of
efficiency. (T/O 4-118.)
■ 143. Drill for Searchlight Section, Semimobile, Peace
Strength. — Under the peace-strength organization only 9
men are authorized for a semimobile unit. No. 4, the tele-
phone operator, and Nos. 9 and 10, the two chauffeurs, are
eliminated. No. 7 (searchlight operator) assumes the duties
of No. 9, and No. 8 (power-plant operator) the duties of No.
10. The duties of No. 4 (telephone operator) are assumed
by No. 3 (acoustic corrector operator) . (T/O 4-118.)
Section IV
NOTES ON THE SERVICE OP THE PIECE
■ 144. General. — a. The service of the piece for antiaircraft
searchlights cannot be conducted with the snap and preci-
sion of a formal drill. There are so many delicate mecha-
nisms involved that an attempt greatly to speed up the
operations of prepare for action and march order will result
only in a great number of materiel failures.
b. It will rarely be necessary to execute prepare for action
or march order with great speed. In all training, stress
should be laid on the saving of time during the operation
of locating and picking up the target — between the time a
target is first heard and the moment it is picked up.
c. The service of the piece is conducted at ease and with
as few orders as possible. Except for the necessary orders,
reports, and instructions, no talking is permitted.
104
ANTIAIRCRAFT SEARCHLIGHT UNITS 144-148
d. The service of the piece as described in the previous
section and tabulated in the drill table, chapter 8, gives only
an outline of the duties of each man at the various com-
mands. A knowledge of what to do must be supplemented
by continued practice until the unit can operate, if necessary,
without commands. The procedure in locating, picking up,
and carrying the target must become second nature if the
platoon is to be capable of coping with multiplane attacks,
pursuit-plane interference, and other stratagems of an at-
tacking air force.
■ 145. March Order. — It is necessary to exercise special care
at march order, as this command is generally given at dawn,
when crews are tired, hungry, and anxious to get back to
bivouacs. Noncommissioned officers must exercise the super-
vision necessary to prevent damage to the materiel, both
during the preparation of the materiel for the road and the
securing of the materiel in the vehicles.
■ 146. Commands and Signals. — Commands are given in the
prescribed form, signals (buzzer, flashlight, or whistle) being
substituted for commands wherever practicable.
■ 147. Safety Precautions. — a. Searchlight operators should
not enter the light when the main arc switch is on. When
entering the light and the parts of the light are heated, the
operator should be fully clothed! and should wear gloves to
avoid injury.
b. Crews loading and unloading the light and power plant
on and off the trucks must keep clear of the equipment be-
ing loaded, so that no one will be hurt if a block and tackle,
winch, or cable fails.
■ 148. Handling Equipment. — a. Since much handling of
equipment takes place under cover of darkness, special care
must be exercised to avoid injury to personnel and damage
to materiel.
b. As soon as materiel is unloaded from trucks it should
be moved off the road. Materiel disassembled for loading
should not be left in the road unless under guard. Cables
should be thrown to the side or off the road so as to avoid
105
148-151
COAST ARTILLERY FIELD MANUAL
damage by vehicles; tractors or tanks passing over a cable
will completely destroy it.
c. Chauffeurs must exercise special care when moving
without lights to avoid damage to equipment or injury to
personnel. When backing the truck, the chauffeur should be
assisted by another member of the crew who walks in
advance of the truck.
■ 149. Action on the March. — a. Members of the search-
light section are given instructions relative to the action to
be taken if attacked while on the march. A single search-
light unit is not a profitable target for low-flying light
bombardment aviation, but units the size of a platoon or
larger are profitable targets.
b. The two automatic riflemen are kept on the alert when-
ever the unit is on the road. In truck No. 1, the automatic
rifleman riding in the forward end of the truck body over-
looking the cab keeps watch to the front and sides. In
truck No. 2, the automatic rifleman riding in the rear end
of the truck body keeps watch to the rear and sides. When
the unit stops along the road, the riflemen leave the trucks
and take position where they can best defend the unit. On
arrival at the bivouac area, the riflemen stay on guard until
all trucks are under cover and they are dismissed by the
chief of section. For further details see FM 25-10.
■ 150. Fall Out. — At drills and practice and in the field
when ample warning of the approach of targets may be
expected, the platoon commander may give the command
fall out. At this command all members of the section
may leave their posts except the telephone operator who
remains within hearing of the telephone bell or buzzer.
■ 151. Dismissed. — When searchlights are to occupy the
same positions on successive nights, the platoon commander
at daylight gives the chiefs of section instructions as to the
securing of equipment, posting of guards, or use of vehicles
as may be necessary, and commands: DISMISSED. The
personnel of the platoon is assembled at its bivouac, usually
with that of the gun battery, for meals and rest.
106
CHAPTER 7
MAINTENANCE
■ 152. Scope. — Maintenance includes inspections, cleaning,
servicing, lubrication, and tightening. "For motor vehicles,
this subject is discussed in detail in PM 25-10. Much of the
information given in that manual will apply to the power
plant.
El 153. Inspections. — a. The chauffeurs of vehicles should
make periodic inspections as discussed in PM 25-10. These
inspections should be made with the idea of finding and
correcting defects so as to prevent the break-down of
equipment while operating.
b. Power-plant operators inspect their power plants
closely following the prescribed routine for motor-vehicle
drivers as given in FM 25-10.
c. Inspections of the searchlight should include a check
on the —
(1) Tires.
(2) Leveling jacks and bubble tubes.
(3) Traversing mechanism and azimuth lock.
(4) Elevating mechanism and transportation bar.
(5) Carbons.
(6) Positive and negative heads.
(7) Thermostat lens.
(8) Fan motor.
(9) Mirror.
(10) Front door glass.
(11) Lamp control box.
(12) Ground glass finder.
(13) Extended hand control.
(14) Main are switch.
(15) Rotary converter.
d. Inspections of the control station should include a check
on the —
(1) Binoculars.
(2) Fit of the binoculars in the! binocular mount.
107
153-155
COAST ARTILLERY' FIELD MANUAL
(3) Binocular mount (including azimuth and elevation
slip clutches).
(4) Elevation drive (including slip clutch).
(5) Azimuth drive (including slip clutch) .
(6) Distant electric control (with power on) .
(7) Zero reader system (with power on) .
(8) Level screws and bubble tubes.
H 154. General Care op Searchlight. — a. The searchlight,
particularly the lamp mechanism and mirror, should be pro-
tected against damage from dust and dirt. It should be
maintained in serviceable condition in accordance with the
best electrical and mechanical equipment practice.
b. All exposed surfaces of insulation should be kept free
from oil, grease, dust, or moisture.
c. All electrical contacts should be kept clean and bright
and free from oil, grease, dust, or moisture. Particular
attention should be paid to motor commutators and collec-
tor rings. A check should be made to insure that all brushes
ride freely in their holders and that they are held by suffi-
cient pressure in order to minimize sparking.
d. Carbons must be kept dry and protected against any
jarring that might crack the carbons or their cores. Until
required for use, the carbons should be kept sealed in their
containers to prevent absorption of moisture. This require-
ment pertaining to cracked carbons should be considered
during the lamp operating period as well as during the han-
dling period indicated above. If a positive carbon protruding
beyond the plane of the front door should be hit accidentally,
the operator should assure himself that the carbon has not
broken between its feed rollers and brush contacts.
B 155. Cleaning Searchlight. — a. After every third change
of carbons: Clean the negative contact surfaces by wrapping
a piece 00 sandpaper once around a negative carbon stub
and working the stub back and forth in the negative head,
with minimum practicable pressure between the negative
contacts. Use the abrasive only to the extent of brightening
the surfaces. After cleaning be sure to wipe off all sand that
might be deposited.
108
ANTIAIRCRAFT SEARCHLIGHT UNITS
155
b. After every tenth change of carbons: Clean the positive
contact surfaces. Remove the positive contacts or brushes
from the lamp by releasing the spring retainer hook from the
upper positive brush, and then removing the current-carry-
ing ribbons for both brushes from the positive casting.
The contact blocks can then be removed and polished by
working a positive carbon stub, wrapped with a layer of 00
emery paper or cloth back and forth through them until
the inside surfaces are clean. Use the abrasive only to the
extent of brightening the surfaces. After cleaning wipe
off all dust that might be deposited. When replacing the
ribbons, polish the surfaces where they make contact with
the positive main frame casting and be sure that they are
tightly fastened at that location.
c. After every 10 hours of operation:
(1) If the lamp has been lubricated with a graphite and
oil mixture, the procedure in (2) below applies. That pro-
cedure will be unnecessary if the lubricant described in
the operator's manual is used.
(2) Place a few drops of a mixture of equal parts of
machine oil and kerosene on the bearings and gears in the
lamp mechanism. This mixture of oil and kerosene loos-
ens the hardened graphite and carries it into the bearings.
(3) Clean off any dust or dirt that may have gathered on
the thermostat lens. Use only a soft cloth which is free
from lint.
d. After every 50 hours of operation:
(1) After 50 .hours of operation and not less frequently
than once every 2 months, the entire lamp mechanism
should be washed thoroughly with gasoline to remove all
hardened graphite. Let the gasoiine evaporate and re-
lubricate the wearing parts as directed in paragraph 156.
This cleaning is not necessary if the lubricant described in
the operator's manual is used.
(2) Clean all motor brushes by removing them and wash-
ing them in gasoline. Make sure the brushes slide freely in
their holders when replacing them.
e. Due to the irregular periods of operation and the varia-
tion of location, no periodic cleaning schedule can be de-
235203° — 40 8 1Q9
155
COAST ARTILLERY FIELD MANUAL
veloped for the following parts. However, they can be
readily inspected and cleaned when necessary.
(1) Clean the thermostat contact points as follows (under
supervision of noncommissioned staff officer) :
(a) Disconnect the two wire leads from the thermostat
terminal block and then remove the thermostat holding bolts.
Take the thermostat out of the drum and place it on a suit-
able flat surface, preferably a desk or workbench.
(b) Remove the four cover screws and the cover.
(c) Loosen the nuts holding the two terminal block screws
and disconnect the wires.
(d) Unscrew the two contact assembly holding screws and
remove the contact assembly.
(e) Clean the points with crocus paper, being very care-
ful not to bend the contact arms and to avoid excessive
rubbing with the abrasive. When finished cleaning, draw a
piece of white paper between the contacts to wipe off any
abrasive that might be left on the points.
(/) Reassemble the thermostat and replace in its position
in the drum in the reverse order to that described above.
(2) The supply and control slip rings should be kept clean
and bright using 00 sandpaper when necessary. Access to
these rings is through the handhole plate In the top of
the base.
(3) The elevation and azimuth zero reader follow-up sys-
tem slip rings should be kept clean and bright. Access to
these rings is through the covers of their respective housings.
(4) The drum should be cleaned to prevent an accumula-
tion of carbon dust or other dirt. Keep the inside of the
drum dry.
(5) Do not allow dust or dirt to accumulate on the lens
of the ground glass finder. When cleaning, use only a soft
cloth which is free from lint.
(6) As its reflecting surface is of precious metal, extreme
care should be employed in cleaning the metal mirror. It
should be cleaned only with the solution especially prepared
for the purpose by the manufacturer. Directions for its use
are provided with the solution. Only clean cotton pads
should be used for applying and removing the cleaning
agent. Do not allow this solution or other moisture or dust
110
ANTIAIRCRAFT SEARCHLIGHT UNITS 155-156
to accumulate on the mirror supporting clips. Before using
the cleaning agent, and also at times as determined by
inspection, accumulations of .dust on the mirror should be
removed with the camel hair brush supplied. Use the brush
lightly in order to avoid scratching the polished surface.
Never wipe the mirror with a rotary motion. Pass the
pad over the surface of the mirror in a radial direction
from the center toward the rim.
■ 156. Lubrication of Searchlight. — a. General. — Due to
the fact that the searchlight is operated at irregular inter-
vals and under wide variations of climatic conditions, it is
impossible to state the exact intervals of time which should
elapse between successive oilings. The various parts of the
equipment should be oiled as necessary. Applying an ex-
cessive quantity of oil must be avoided, especially where a
film of carbon dust might form and cause a breakdown of
the electrical insulation. Prom time to time any excess
oil and grease that may work out of the parts should be
wiped off the operating and control mechanisms, special
attention being given to the edges of the insulating plates
on the lamp. Make sure that there is never any oil or
grease on motor brushes, brush holders, commutators, or
field coils. Never put oil or other lubricant on the slip rings
and slip ring brushes in the base nor on any other electric
conducting surfaces. The parts should be lubricated as in-
structed below.
b. (1) If the lubricant described inl the operator's manual
cannot be obtained, the lamp may be lubricated with pow-
dered graphite thinned with sufficient oil to make the lubri-
cant run into the bearings. Never use plain machine oil on
the bearings of the lamp, because at the high operating tem-
perature of this equipment it would quickly vaporize and
leave a deposit which in time would cause the bearings to
bind. When the lubricant described in the operator's man-
ual is used, it should be applied when the lamp heads are
hot, by means of the spray gun to be found in the spare
parts box. Particular attention will be paid to the lubrica-
tion of all pinions, gears, and universal joints of the positive
and negative heads.
Ill
156
COAST ARTILLERY FIELD MANUAL
(2) The blower motor bearings are accessible after re-
moving the blower motor and ventilation fan housing. They
are grease-sealed bearings and do not require frequent at-
tention. A small quantity of medium motor oil should be
added at the time the motor is inspected for condition of
brushes, brush holders, commutator, etc.
(3) The feed motor bearing ((24), fig. 11) should be oiled
with a good grade of light machine oil. The oil point is
painted red and covered over by a small protective cap.
The ball bearing at the drive end receives grease from
the worm gear housing. As this motor is located on the
drum, lubrication of its ball bearings should be given fre-
quent attention.
(4) The feed motor worm gear housing (near (235), fig.
11) should be filled with a suitable high temperature grease
which can be applied by removing the cover.
(5) The feed mechanism bearings contained within the
control box located on the side of the drum should be lubri-
cated by placing a few drops of light machine oil in the oil
holes provided (near (22) and (235), fig. 11). These holes,
which are marked with red paint, are accessible when the
door of the control box is opened.
(6) The eccentric, fork, and pawl guide is oiled nor-
mally through the hole under (6), figure 11, using light
machine oil.
(7) The trunnion bearings located at the upper end of
the trunnion arms are greased by means of alemite fittings.
The fitting on the right trunnion arm is clearly marked by
red paint. The left trunnion arm bearing does not have
an alemite fitting and may be greased only after removing
the elevation data receiver housing and associated bearing
plate.
(8) The azimuth bearings, on which the trunnion arms'
unit is pivoted, are packed with grease when the search-
light is assembled at the factory and need not be supplied
with additional grease for several years.
(9) The chassis steering gear bearings are greased by
means of standard alemite fittings. These fittings are all
easily accessible.
ANTIAIRCRAFT SEARCHLIGHT UNITS 156-158
(10) The elevation control mechanism located on the
right trunnion arm should be greased through the alemite
fitting provided (marked with red paint).
(11) The azimuth worm, housing located between the azi-
muth gear in the base and the azimuth control motor should
be greased occasionally through the alemite fitting provided.
(12) The azimuth and elevation control motors ((49) fig.
11) are provided with oil holes covered by plug caps. Re-
move these caps and oil the bearings occasionally with a
good grade of medium motor oil.
(13) The dynamotor (rotary converter) hearings are ac-
cessible after removing the cover plates at each end of the
machine. These bearings are packed with grease which
should be replenished occasionally as determined by inspec-
tion. (See (328), fig. 21.)
(14) The chassis wheel bearings are packed with grease
at the factory and will not need much attention as they are
grease-sealed. The outside bearings are accessible after
removing the hub cap and bearing cap. To grease the inner
bearings remove the thrust bolt and wheel from the axle.
c. The bearings not mentioned in b above have been
checked and greased at the factory and will probably not
need any additional attention for the life of the equipment.
■ 157. Tightening of Bolts, Nuts, and Screws. — There is
little likelihood that nuts, bolts, or screws will work loose
during the actual operation of the searchlight. However,
while being transported, the searchlight parts are subjected
to stresses which may cause some nuts and screws to become
loose. It is important that a check be made periodically
and that loose parts be tightened. This check should be
made at the end of a rough trip and after every 500 miles of
transport. In tightening, excessive pressure should not be
applied on the tightening wrenches or tools so as to strip
threads, deface the nut surfaces, or mar screw slots.
■ 158. Cleaning of Control Station. — a. All working parts
of the control station are inclosed except the azimuth gear
and pinion which should be cleaned with a brush and gaso-
line every month. These latter parts should not be greased
113
158-160
COAST ARTILLERY FIELD MANUAL
as greasing will cause dust to gather in the gear teeth.
Alcohol should be used for cleaning the elevation and azi-
muth transmitter rings. If these rings are rough, smooth
them with 00 sandpaper.
&. The contacts on top of the tripod and those on the
under side of the control unit should be cleaned with alcohol
as needed.
c. The slip ring and brush assemblies in the tripod are
accessible after removing the handhole cover plates ((219),
fig. 10). The brush assemblies (not the individual brushes)
should be removed to clean the slip rings. These rings
should be cleaned with alcohol every 6 months.
a. The distant electric control transmitter rings and seg-
ments should be cleaned with alcohol every 3 months. Use 00
sandpaper, if necessary, to-clean any burned spots.
e. (1) If the cover has been removed a number of times
in the field, the control unit should be given a general
dusting and cleaning.
(2) All electrical contacts should be clean and bright.
Clean these contacts with alcohol where necessary. Wipe
off all contacts carefully after using an abrasive (00 sand-
paper) . Do not permit oil to gather on the insulation.
(3) About once a month extend the column to its maxi-
mum height and clean off any dirt or foreign material that
may have accumulated.
(4) If the apparatus is used in a warm or tropical climate,
remove the cover about once a month and clean, removing
all moisture and any sign of fungus growth.
■ 159. Lubrication op Control Station. — Due to the fact
that most of the control unit mechanism bearings are grease -
sealed at the factory, little attention to these parts will be
required. When the control unit cover is removed for clean-
ing operations, the gear teeth and bearings should be in-
spected and a few drops of light machine oil applied as
necessary.
■ 160. Cleaning of Sound Locator, M2. — a. (1) The sur-
face of the metal sight mirror should not be cleaned any
oftener than necessary because of the danger of scratching
the highly polished surface. However, dust which settles on
114
ANTIAIRCRAFT SEARCHLIGHT UNITS 160-1C1
this surface may be removed by absorbent cotton. If the
mirror becomes greasy, it may be cleaned with absorbent
cotton moistened with alcohol.
(2) In the event that the mirror surface becomes excep-
tionally dirty during servicing or field operations, the surface
may be cleaned by mixing 3 ounces of precipitated chalk
with 8 ounces of a good grade of denatured alcohol. Place
a small amount of this mixture on a piece of absorbent
cotton which has been previously moistened with alcohol,
and rub lightly over the surface of the mirror using a cir-
cular motion. After the paste is partly dry, remove with
clean, dry, absorbent cotton. Precipitated calcium carbonate
may also be used for this purpose.
b. Surfaces of the slip rings, should be inspected periodi-
cally and, if necessary, cleaned with alcohol and a soft
cloth.
c. The rubber eye-shield on the sight should be removed
periodically, washed in lukewarm water, and dusted over
with French chalk or equivalent as a preservative.
d. The horns and acoustical system should be kept free
of water, dirt, or other foreign matter at all times. This
does not mean that the equipment may not be used during
rain, but that it should be checked prior to packing or
storage.
e. Plugs and receptacles should be kept clean and when
not in use should have their protecting caps bolted on.
tightly.
■ 161. Lubrication op Sound Locator, M2 — a. Referring to
figure 34, points (38) are lubrication points. Periodic in-
spection and lubrication will insure proper functioning of
the equipment. It is recommended that light machine oil
be used for this purpose.
b. Points (40) and (41), figure 34, indicate chain drives
for operating the pantograph drive assembly. Periodic
inspection and greasing of these chains should be made to
insure proper operation. Removal of the coyer plate will
provide access to this section.
CAUTION: Care should be exercised to prevent applica-
tion of too much grease during this operation, to lessen any
115
161-162 COAST ARTILLERY FIELD MANUAL
possibility of the excess lubricant being thrown onto the slip
ring assembly.
c. Differential gears and ball races have been lubricated
at the factory and no attention need be given these points
except by authorized ordnance personnel during overhaul
periods.
CAUTION: Particular care should be taken to prevent
inclusion of any foreign matter within the main case during
servicing operations.
d. All operating personnel should be cautioned against
tampering with the mechanisms of the sound locator, es-
pecially those of the corrector drive assembly and the
pantograph drive assembly.
Figure 34. — Lubrication, sound locator, M2.
■ 162. Lubrication for Power Plant. — a. The more impor-
tant points; of lubrication and the methods are given in b
below. (See fig. 35.) More detailed instructions will be
found in the instruction manual for the particular power
plant concerned.
116
ANTIAIRCRAFT SEARCHLIGHT UNITS
162
b. (1) Air cleaner. — Clean once every week or more fre-
quently if operated in dusty or insect laden atmosphere.
(2) Charging generator. — Add only 2 or 3 drops of light
oil every 50 hours of operation.
(3) Distributor. — Add a few drops of light oil every 50
hours of operation.
STARTING
CRANK
MOTOR CONTROL
CHARGING
GENERATOR
GOVERNOR &
THROTTLE LINKAGE
AIR CLEANER
FAN MOTOR
GENERATOR
BEARING
Figure 35. — Power plant lubrication chart.
(4) Engine erankcase. — Check and maintain oil level be-
tween the three-fourths and full mark.
(5) Fan motor bearings. — Add a small amount of cup
grease every 6 months.
(6) Generator bearings. — Add a small amount of cup
grease as required.
(7) Governor linkage. — Add a few drops of light oil every
50 hours of operation to ball joints and other moving parts.
(8) Oil filter. — Change the filter cartridge as soon as black
streaks appear in the oil.
117
162
COAST ARTILLERY FIELD MANUAL
(9) Tachometer drive. — Add cup grease every 6 months.
(10) Water pump. — Give grease cup one turn every 50
hours of operation.
(11) Motor control. — Add a few drops of light oil to sole-
noid hinge pins every 50 hours of operation.
(12) Starting crank. — Add a few drops of light oil when
required.
Lubricait Every 1000 Miles
FAN BEARINGS 5
Lubricait Evtry 1000 Milts
GOVERNOR E
Lubricait Evtry 1000 Miln
ENGINE E
heel oil Icvtl^r^W mTta
Change oil it required
.ubricatt Evtry I20OO Milts
WHEEL BEARINGS 5
; uhrie&r Ei'rtu 1000 Miln
STEERING KNUCKLES C
Ea<h»idc
Lubntur,- Li-try 1(100 Miles
TIE ROD C
Each »dc
l.uhncalt E itry 1000 Milts
BRAKE CABLE C
E«h iid<
Lubricait Every I0O0 Milts
DRAG LINK C
Lubricait Evtry ICOO Milt)
FRONT SPRING PIN C
Lubricait Evtry 1000 Mitel
STEERING GEAR 5
Lubricait Every 1000 Milu
PEDAL SHAFTS Q
l.vbncnrc Evtiy 1000 Witt
RADIUS ROD Q
Two front, tub lid*
One r»i. each »dt
Lubncatt Evtry 1000 Miln
REAR SPRING SHACKLES Q
Each lidt, front and rrjr
Lubricait Entry 1000 Miltt
ONTROL
SHAFT '
Each lidt
■MitEvttu 12000 Miln
DIFFERENTIAL 5
■3 WATER PUMP SHAFT
Lubricait Every 1000 Milt,
C FRONT SHACKLES
Each side
Lubruatt Every 1000 Milti
C BRAKE CAMS
Each lidt
Lubricait Every 1000 M,tt<
E GENERATOR
17 Lubricait Every 7000 Mile*
^ DISTRIBUTOR
O Create Cup (wo turn!
Engine Oil on Breaker Pivoi
Vaseline on Face of Cam
Clean Evtry 1000 Milts
OIL FILTER
Clean when changing crankexe o
Lubricait Evtry 1000 Miltt
E STARTING MOTOR
E AIR CLEANER
Clean and add oi! in con taint r
Lubritalt Every i000 Milts
$ POWER CYLINDER
S« Sprcifitniom
hubficait Evtry 1000 Milts
S CLUTCH
Turn Grease Cup several mini
Lubricate Every 12000 AMrs
5 TRANSMISSION
Special Gear Oil. Add as rtquurrJ
Flash and refill every 1 2.000 rmU
Lubricate Entry 1000 Miles
6 FRONT AND REAR
UNIVERSAL JOINTS
POWER GENERATOR
S— 0parato*a' WjuwI-
Uibricatt Evtry 1000 Mil. -.
Q HAND BRAKE PINS
Lubricate Eftry 12000 Miln
C REAR WHEEL BEARING
Lubricate Every 1000 M.lts
CFRONT AND REAR
SLIP JOINTS
S Spaeial Gnaw
E E"fi«<
C Chaaaii Lubricant
Figttre 36. — lubrication chart, power unit M1934.
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