military searchlights (1943)

8/22/2019 Military Searchlights (1943)

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Fl'1 4-115

COAST ARTILLERYFIELD MANUAL

ANTIAIRCRAFT ARTILLERYOPERATION OF l\:IATRIEL

AND EMPLOYMENT OF PERSONNEL,'NTIAIRCRAFT SEARCIILIGHT UNITS

PREPARED UNDER DIUECTION OF THECHIEF OF COAST ARTILLERY

UNITED STATESGOVERNMENT PRINTI~G OFFICE

WASIIINGTON: '910

;---------------------IIrMilloby tho Supt~rlntendlmt or I>oruml'nts. WaHhlnlCton. D. C. Price 35 ("('nla


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WAR DEPARTMENT,WASHINGTON, June 20, 1940.

PM 4-115, Coast Artillery Field Manual, Antiaircraft Ar~;iIlery, Operation of Materiel and Employment of Personnel.IUltiaircraft Searchlight Units, 1s published for the 1nforma~Jon and guidance of all concerned.

lA. O. 062.11 (5-1-40).]By ORDER OF THE SECRETARY OF WAR:

O. C. MARSHALL,Chief 01 Staff.

OFnCIAL:E. S. ADAMS,

Ma10r General,The Ad1utant General.

II


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TABLE OF coNTENTSCnA Paragraphs

~TER' 1. GENERAL.ection I. General__________________________ 1- 5Cn II. Aerial sound ranging-------------- 6-12~PTER 2. TRAINING.ection I. General -------- 13-17

II. Selection of personnel_____________ 18-23III. Individual training 24-31IV. Section training..;------------------ 32-41C V. Platoon training 42-62

~PT~R 3. OPERATION AND FUNCTIONING OFAT.,;RIEL.Section I. Sound location equipment--------- 53-58II. Control station 59-61III. Searchl1ght------------------------ 62-67IV. Power plant 68-72

C V. Vehic~es 73-77~~PTER 4. PREPARATIONSFOR ACTION AND FOR~vJ.OVEMENTSection i. Preparing for action 78-94

II. Orienting and synchronizing------- 95-99III. Preparing for the road 100-108C IV. Protective measures------------- 109-111n~PTER 5. ORGANIZATION.ection 1. Searchlight battery 112-113II. Searchlight platoon 114-115C III. Searchlight section 116-117nAPTEa 6. SERVICEOF THE PrECE.Section I. Searchlight platoon action------- 118-126II. Duties of personnel 127-129

III. Dr1ll of searchlight section 13(}-143C IV. Notes on service of the plece 144-151C:::;ER 7. MAINTENANCE 152-163J\PPENER B. DRIL TABLEINDEXDIX.LIST OJ"REFERENCE:---------------------------------------------------------------------------

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COAST ARTILLERY FIELD l\IANUALANTIAIRCRAFT ARTILLERY

CHAPTER 1GENERALS Paragraphs

teTION T. GeneraL______________________________________ 1-5II. Aerial sound ranging___________________________ 6-12SECTIONIn1


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14 COAST ARTILLERY FIELD IlIANUAL! Its apparent direction, this Is not sufficient for theof the searchlIght because of the inherent directIOnal inac"1, curacy of the human ear. The apparent source of the soundI is constantly moving,and the sound itself is subject to a lag'I because of the time necessary for the sound wave to travel, from Its source to the point of reception. It is advisable,larder 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 andlather effects be applied, and that a prediction be made ofI the true position of the target. Where the searchlight andI the sound locator are so connected together electrically thatI the searchlight may be moved with the sound locator! azimuth and elevation, prediction may be continuous andI automatic. Aerial sound ranging is the process of locating'the aircraft by means of the sound emitted. Aerial soundranging is used primarily at night to assist searchlightslocating targets in order that they may be illuminated witllthe minimum delay. .! The position of the target is determined when the azimutb,! 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 illuminatioIlat night by means of sound location and searchlight

: nation should-(1) Determine with the greatest possible accuracy the

angular height and azimuth of the apparent source of the, sound.I (2) Determine the effect of sound lag on aZimuth and ele"; vation so that the appropriate corrections may be applied.I (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 thetarget, due to distance between searchlight and soundlocator. .(5) Apply the corrections continuously and without anfloss of time.(6) Transmit automatically and continuously to thesearchlight the corrected SOU:d locator data.

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ANTIAIRCRAFTEARCHLIGHTNI'IS 4-7(7) Move the searchlight continuously in azimuth and~gUlar height so as to follow the moving point source ofe sound.illc. The present standard system of target location anditUlnination embodies means for accomplishing all exceptSetln (3) of the requirements indicated in b abOve. Noa. iSfactory correction device has been developed for deter-~lning and applying corrections for the deviating effects one Sound wave caused by atmospheric conditions.

d.i d. The method of position finding by sound location IssCUssedin connection with the sound locator and acousticCorrector in paragraphs 7 and 26.1 5. EQUIPMENT.--a.The complete system for the detection,location, and illumination of aerial targets includes the fol-~:ing equipment, the arrangement pf which is shown sche-tically in figure 190:(1) Searchlight.(2) Power unit( .


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'7-9 COASTARTILLERYIELDMANUALImine the direction of a sound source by means of the binauralI sense. When a man stands in the open where he is notIbothered by echoes, he can determine by his sense of hear"I ing alone the approximate direction of the source of a sound.IHe does this instinctively by turning his head so that he willI face the apparent source of the sound. This is largely ac-counted for by the fact that the human ears are separatedI by about 5% inches; hence any sound, unless originating inI the perpendicular plane bisecting the line joining the twoI ears, will arrive at one ear before it does at the other. The \! human ear is sufficiently sensitive to detect this time dif-lference, and the listener's binaural sense tells him that the, sound originated on the side which the sound flrst reached.I It is to make the sound arrive at both ears at the same'! time (and thus eliminate the time difference) that the headI is instinctively turned until the sound is faced. When the;I sound locator is used, the sound source usually appears tothe listener to be directly in rear of his head when the horns,'. are pointed toward the source.II.8. SOUNDDISTURBANCEs.-Soundtravels through the at ..mosphere, and the sound waves are affected by everYchange and departure from uniformity in the transmitting!medium. The atmosphere itself is always in motion. Any-lthing such as Wind, density, or temperature changes whichcause the sound wave to drift or bend will produce an error: in the determination of the direction of the real soundI source and consequently must be corrected for. The most', common causes of the displacement of the sound waves, fromthe path and shape which they would have in a st1ll, uniformatmosphere, are wind drift, wind refraction, and temperature'refraction. f 9. SOUNDLAG.-Sound travels through air of average tem"perature at about 1,100 feet per second which is less thanhalf the muzzle velocity of the antiaircraft guns. Soundmay thus be said to have a "time of flight." As the targetcontinues 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'II

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ANTIAIltCRAFTEARCHLIGHTUNITSsPeed of the target, and the average temperature of the aiWhich determines the velocity of the sound. At 300 F. thiVelocity is 1,022 feet per second, and at 1000 F. it is 1,166feet per second. The velocity changes about 1.1 feet peSecond for every degree (Fahrenheit) change of temperatUre. For the calculation of sound lag time for varioUs altitUdes and angular heights, an average velocity of 1,100 feePer second can be 'used without introducing an error of anConsequence. Such a velocity will not be far from the average since we deal mainly with the lower temperatures aftenightfall and at the higher altitudes. Slant range in feediVided by the velocity of sound waves in feet per secongives the sound lag time in seconds.II 10. ATMOSPHERICCORRECTIONs.-The effects of wind driftWind refraction, and temperature refraction on the sounWave have been discussed. While these effects are known teXist and while their correction is highly desirable, the prob-lem of developing a satisfactory correction device has nobeen completely solved. The amount of displacement causecan be computed. However, the basic information on whicthese computations must be based is either not available 0is generally quite unreliable . 11. SOUNDLAGCORRECTIONs.-Corrections for sound lag ardetermined and applied by the acoustic corrector. Thoperation of the corrector in connection with the sounlocator determines and applies the correction for sound lato the azimuth and angular height as determined by thSOund locator. These corrected data are transmitted elec-trically to the control station, enabling the controllers toPOint the light in the direction indicated ... 12. PARALLAXCORRECTIONS.-a. The location of the

ltlULS 01 tne system. "lUe magnnuue 01 Llle parallax enectWill depend upon the distance separating the two units, upon

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,2 COAST ARTILLERY FIELD MANUALhe slant range to the target, and upon the direction of thearget with relation to' the line joining the two units.I b. The azimuth parallax correction is of considerable im- .lortance in prediction by sound location. The separation)f the sound locator and the searchlight by a considerablelistance is necessary in order to reduce the disturbing noises~hich interfere with the operation of the sound locator. Its desirable that the parallax correction made necessary byiUch separation be introduced automatically into, the cor-~ecteddata. The effect of azimuth parallax may be greatly~educed by setting up the unit with the line searchlight-;ound locator pointed in the direction of the targets' ex-~ected approach.. c. Instructions for computing and applying parallax cor-~ectionsare given in paragraph 54b.

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CHAPTER 2TRAINING paragraphs

SECTION I. General l:=~;II. Selection of personneL_______________________ 4-31III. Individual training--------------------------- 22-4IV. Section training------------------------------ 32-5~V. Platoon training 4

SECTIONGENERAL

.' 13. SCOPE.-ThiS chapter contains Suggested methods ofselection and training of personnel designed to secure rapidand efilcient lllumination of SUitable aircraft targets . 14. IMPORTANCE.-Allctive countermeasures against nightflYing aircraft, both by pursuit aviation and antiaircraftartillery, depend on searchlights for the 1llum1natlon of theirtargets. Without thLc;illumination the most elaborate sys-tem of air and ground antiaircraft defense is useless.II 15. TARGETS.-a.Antiaircraft searchlights are primarilydesigned to illuminate aircraft flying at medium and highaltitudes-normal targets for the antiaircraft gun. Theiradditional mission is to illuminate low-flying aircraft-thoseWhich are the normal target for automatic weapons. Pri-lnary targets must be illuminated at such a distance from theobjective as w11lpermit the fire-control instruments of thegUn batteries involved to pick up the target ar.d track it,~nd the guns to open fire so that the first shells burst athe maximum effective range of the guns.b. Antiaircraft searchlights also cooperate with friendlyatVlationby 1llumina,ting targets for pursuit aircraft, enablinghe friendly pursuit to find and attack the enemy.II I 16. LO~ATINGHE TARGET.-The short time available fortracking the target prior to illuminating it makes it 1m-1lerative that the methods used in locating the target be

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.6-20 COASTARTILLERYFIELDMANUAL~imple, accurate, and rapid. Practice in locating targets;hould include training to identify, as well as locate, the;arget by sound. The theory underlying these methods of:arget location is discussed in detail in FM 4-111.I) 17. SELECllIONANDTRAININGOF PERSONNEL.-Efficient op-;ration of searchlight materiel requires that personnel bel';arefu1ly selected and thoroughly trained. In order to allow;or inevitable losses due to promotion, sickness, and casual-:ies, each keyman must have at least one understudy trained.is his replacement. Selection and training of personnel are~iscussed in detail in the follOWing sections.

SECTIONIISELECTION OF PERSONNEL

18. LISTENERQUALIFICATIONS.-The men of the searchlight)attery who must be most carefully selected are the listenersNho operate the sound locators. They must have good:learing, be alert,be able to concentrate without tiring, andpossess at least a normal ability to locate the direction of j~he source of a sound (binaural sense). ., 19. TEST OF HEARING.-The first step in selecting listenersis to give every available man in the battery an examination.n hearing. ThIs should be performed by a medical officer Ilsing an aUdiometer. A record should be kept and the menclassified as follows: those with 20/20 hearing in both ears,those who do not have balanced ears, and those who havepoorer than 20/20 hearing. Men who do not possess satis-ractory acuity of hearing in each ear, and who have notapproximately the same acuity in both ears, should not beselected as listeners.II 20. BINAURALTEST.-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


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ANTIAIRCRAFTEARCHLIGHTNITS 20- 21eating it using the intensity sense (the difference in loudnes1n each ear).b. (1) The following demonstration will show how thebinaural sense functions and how it differs from the inten-sity sense. A group of 10 to 20 men is arranged in a largeCircle, facing inward, and with eyes closed. The instruc-tor takes position just inside the circle and calls on variousInen by name to point to him, locating him solely by theSound of his voice. After the men have the idea, one-halfthe men are allowed to watch the other half locate theinstructor by sound. This will not only give all an idea of'\\Thatis meant by locating a sound, but will show that prac-'tl~ally all men possess this sense.~(2) After all men have demonstrated their ability to lo-Cate a fixed sound


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21- 22 COASTARTILLERYFIELD MANUAL,possible in the circle. During all these tests the candidatesishould be marked on alertness, accuracy, and general ability.to do what is indicated.

FiGURE I. BInaural training lnstn nlent, MI . 22. BINAURALTRAINERTEST.-TI1l' binaural training in~tru-ment (fig. 1) affords a means of measuring binaural abilitynumerically and therefore is very convenient for comparingthe ability of the various candidates. Each candidat. isgivrn a few trial runs to make sure that he knows what isrequired. As the candidate turns the handwheel, the soundwill seem to move across the back of the skull from one eart.o the other. When the sound is properly centered, itshould seem to be at the base of the skUll, midway betweenthe two ears. In sam obs('rve1's the sound will seem to becoming from the frollt-in others from the rear, but thisis an individun I idiosyncracy and has no dIed on accuracy.Th important requirement is that the sound be cenL


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ANTIAIRCRAFTEARCHLIGHTNITS 22- 24midway between the ears and at the same place on everYtrial. Most learners find it helps to bracket the sound, thatIs, rnove the wheel until the sound seEms to be a shortdistance on one side of center, then move the wheel in theoPposite direction until the sound is definitely nearer theother 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 soundSOUrce.The candidate endeavors to keep the sound centered duringthe test by moving his handwheel t,he proper amount andIn the proper direction. At least five test runs are thenmade and the results recorded . 23. SOUNDLOCATOREST.-As a result of the tests leadingUp to and including the binaural-trainer test, the numberOf candidates should be cut down to about three listenersPer pOsition available. Those selected should be tested onthe sound locator. As a sound source, the loud-speakereqUipment of the binaural trainer, M2, or a moving truckor car at a distance of 100 yards or more affords a goodSUbstitute for an airplane, without introducing the compli-cations of sound lag. As a result of these tests, the numberof candidates should be reduced to about double the number~f Positions available. With these listeners, individual train-ng is commenced. SECTIONIII

INDIVIDUAL TRAINING OF PERSONNEL24. PHASEs.-Tbe training of personnel is divided . intothree phases: individual training, unit training, and platoontraining. In the first phase, individuals are perfected in the~chniqUe of their individual duties. In the second, the menanning one searchlight unit


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COASTARTILLERYIELDMANUAL5- 26 25. LrSTENERS.-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 listenerSshould flrst 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 trainingthe locator, flrst on a vehicle target at short ranges 000-500yards) and later on airplane targets at increasing ranges:Here the instructor may use considerable initiative incuring suitable targets by setting up the locator nearairfleld, near a road along which automobiles travel, or neatthe shore where power boats are in use. }

b. Once the listeners clearly understand what is requireof 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: pursuitplanes, observation planes,' bombing planes; one-, two,-four-motored planes; planes flying singly and inc. As air commanders expect to "screen" their high-flyinltibombers by lower-flying formations of other. planes, theteners must be trained to pick up the bombers through thescreen. 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 meanSof the sound heard. A two-motored flying boat will make g,1very different sound from that made by a two-motoreJbomber. Two single-motored planes flying close togethet'can be distinguished from one two-motored plane.with liquid-cooled engines which have an even number ofcylinders can be distinguished from those with air-coole~engines which are generally made with an odd number ofcylinders. Engines of different size emit different sounds. 26. ACOUSTICCORRECTORPERATORS.-Topermit the frequent relief of listeners, the acoustic corrector operatornormally 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 corree:tlons In the transmission of a::urate da~a to the searChllghl

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anTRUE POSITION APPARENT POSITION

COURSE OF TARGET) DETERMINED BY SOUJ O........ -.---- FRA'VU-omRGET=r--

LOCATORFIGURE 2.-8ound lag correction.

27. TELEPHONE OPERATORs.--a. The primary qualificationsS01' a telephone .operator are good hearing and the ability tosPeak clearly and correctly. Most men do not have theecond qualification naturally but must be trained in speech.'[he pronunciation of numbers for telephone use ("fo-wer"cor four, "ni-yen" for nine, etco>. the use of words to indi-ate letters of the alphabet ("affirm" for A) , and the general

235203~- - 4O- - - - 2 13

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17-28 COAST ARTILLERY FIELD MANUAL", I;)rocedure for efficient telephone operation as given in F1J!24-5 should be included in the training.b. In addition to the general training mentioned above,che operator should be afforded a great deal of practice ill.che use of words, commands, and warnings usually employedin 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 antiaircraftcommunication, the operator does not ordinarily record the.essage received, but repeats the messaga orally as it comeSover the wire. Similarly, messages from the chief ofo the platoon ccmmand post are not recorded but arepeated as given by the chief of section. Exception is made

in the ~ase of administratIve messages (messages relatingsupplies, repairs, etcJ 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 tomake simple repairs should be given the operatpr. Hehave practice in diagnoSing simple troubles in the telephone

line and in recogniz1ng the symptoms of a short circuit, anj

open circuit, or other source of trouble. For details see FM:~;. CONTROL STATION QPERATORS.-a. (1) 'lne azimuth aJelevation cc:mtrollers should be trained to keep the.light pointed as indicated by the sound locator. Thisaccomplished by using the handwheels to keep thereaders centered. They should be cautioned to avoid radica1movements and to smooth out any sudden movementsfor by the zero readers. They search for the targetslowly and smoothly moving the zero reader pointers firstone side and then to the other side of the zero mark.

(2) The $earchlight commander (generally a noncom~missioncd officer) looks through the binoculars and dlrect~the search for the target. He should be instructed as to thesize of the area of error through which thesearch. This area of error may be assumed as 100 inameter (searchlight beam Is about H'4 in diameter) for14

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ANTIAIRCRAFTEARCHLIGHTUNITS 28- 3new locator crew and 50 for an experienced locator crew. IIis then shown how to use the binoculars on the control sta

\ ~i~n i? an active search and how to carry the t~rget aftc1t 18PIcked up. He should be instructed as to the Importancof a slow and careful search, as many unseen treks are mabecause the search was too fast and the flick too short .. b. The details of the actual operation of the control stabon are given in paragraphs 59 to 61, inclusive.I; 29. SEARCHLIGHTOPERATORS.--a. The searchlight operatoS?OUld be trained in all the details pertaining to the func:boning of the searchlight. He should be taught the pre'Scribed method of-(l) 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. 63j).(5) Keeping the positive crater at the focal point of thl

lnirror (par. 63c).(6) Keeping the arc voltage and current at the propeValues (par. 63c)'(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

ciont instruction and drill on the manual control of thsearchlight and its arc, in order that the change from autolllatic to semiautomatic or manual control may be madWithout confusion and loss of efficiency. Even though thautomatic devices usually function perfectly, complete rcliance must not be placed on them.c. Detailed instructions for the operation of the searchlight will be found in paragraphs 62 to 67, inclusive.II 30. POWER-PLANT OPERATons.--a. Each power-plant opelator is first trained in the mechanics of starting, runnin(and stopping the power-plant engine. He is then trained tOperate the power panel and to keep the power planttOad operating condition.b. lIe is thoroug-hly trained in the manual operation of tb})OWer plant to insure its continued operation in case tl1

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lh13 COAST ARTILLERY FIELD MANUAL~utomatic devices fail. Manual operation requires frequentlractice and a high degree of mechanical skill to operate.he power unit efficiently.c. Detailed directions for power.plant operation aren paragraphs 68 to 72, inclusive.I 31. CHAUFFEURS.-a.The majority of enlisted men todaYlave had some experience in driving an automobile. They!ihould be first taught the difference between a passenger carmd the truck they are to operate. The difference in height,ength, and weight should be pointed out so that. they willlot attempt to drive the truck through an opening too small:or it. The greater length will make it impossible to get:lround hairpin turns easily negotiated with a car. The~reater weight calls for greater care as to bridges tried andDuddy roads used.b. ~ew 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 ...::ate the truck. 1c. They ~hould be given an understanding of what net to:10; that they should not adjust the carbureter, adjust thebreaker points, clean the spark plugs, or attempt to makeother repairs normally attended to by the battery mainte.lInance section. .

SECTIONVSECTION TRAINING

32. SCoPE.-The training of the section should prOVidein.struction in the teamwork of operating one complete search.light unit efficiently. 33. METHOD.-a. Given proper individual training, themost important factor in unit training is practice. Practicemust be at regular intervals and cover all the different sltua.1Itions the unit is likely to encounter in action.b. The importance of frequent practice at regular intervalscannot be overemphasized. It has been found that a breakof a few days in training seriously lowers the efficiency of aunit. To prevent these breaks in training, the unit com.'

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ANTIAIR,CRAFTEARCHLIGHTNITSlllander must use all possible ingenuity. The binaural trainininstrument, M2 motor vehicles motor boats, and commerc1a ' 'tnd military airplanes must constantly be employed to fill 1he periods where no regular drills on assigned targets ar})ossible. .34. CHIEFSOF SECTION.-Chiefs of section require carefu';:;lnlng in order to be able to operate their units properlyeir training should include the subjects listed below.a. Acoustics should be covered in enough detail so that thChief of section can understand and explain-

t (1) Travel of sound in air, and how its speed varies wit!emperature.(2) What sound lag is, and why we correct for it.f b. Atmospherics should include an idea of the generalormation of the atmosphere how its density varies with~ltitude, why winds from vari~us directions affect the read-ngS of the sound locator, and the corrections to apply forWinds from various directions.c. Map reading is essential, as the section commanderlllust 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 toclimb.(3) Whether a nearby knoll is high enough to blanket aprospective light position.t d. Tactics and speed of modern aircraft of the differentypes.e. Selection of a good searchlight position as described})aragraph 80..35. SEARCHLIGHTOMMANDERS.--a..he principal emphasisn the training of the searchlight commander should be})lacedon the search for the target. He should know enough

lllumination phenomena and sound phenomena


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35-36 CO.'5T ARTr..LERY FmLD MA>lUAL!search and how to apply correction::; fm' i:1div~dual listeners'!errors.I b. He should know enough about the c.esig:l and function"ing of the searchlight, control station, and power plant to.Isupervise their operation and routine maintenance.c. He should be trained to be able to take over theof the chief of section, should this become necessary.,1136. LIsTENERSANDACOUSTICCORRECTORPERATORS.-a.OIla normal course, the operators will find that events,occur in the following sequence:I (1) The listeners at advanced listening posts (severa,miles to the front) will report a target coming in and itSgeneral location as to azimuth ana. estimated altitude.I (2) Aided by this report, the chief of section directs:listeners to move the locator horns to the generalindicated and to search (move the horns up and down,I and left> in that general vicinity. In the usual case, itI be possible to hear the target with the unaided ear:picking it up with the locator. Coached by the sectiOIchief, the listeners pick up the target in their horns.Ieach listener centers the sound of the target, he reports "allI target." This will generally occur when the target is be}I tween 10 and 20 above the horizontal.I (3) At the section chief's. command TRACK,he acousticcorrector operator operates his instruments, sendingrected sound locator data to the light.(4) At the command IN ACTIONgiven by the chief oI section (normally by whistle), the light is turned on andI search for the target begun. This command is generall~, given when the target is from 30 to 450 above the hori''zontal. During this searching period, the listeners and cor}I rector operators continue as before, sending corrector dat~: to the control station.I (5) The target will next be picked up and carried. TbeI listeners and operators cease tracking and turn the locatof, to the front, ready for another target.(6) At the command OUTOFACTION,he light is put out.

b. It Is Important th.t the listeners center the sound .'the same place each time, that Is, midway between the ears:18

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ANTIAIRCRAFT SEARCHLIGHT V~ITS 36-'leaving the section chief to determine and apply the corretion necessary for the particu!ar individual. Every oppotunity must be taken to check on this individual correcticas it is subject to a gradual change especially while a listenis learning. This checking may be done whenever tllisteners are tracking a target, and the target may be seeby looking through the open sight on the light. If the targis not seen at the center of the sight, and this difference (individual correction) remains approximately constant fro~ay to day, it should be recorded and applied whenever th,lIstener is on duty.c. As an aid to training the locator corrector crews, tllight units can be set up (at night) close to each other. 'I1target plane is directed to leave its running lights on. Tllights are pointed on sound locator data. The amount tllight beams miss the target is an indication of the errorthe sections. The gradual decrease in the size of this err(as training progresses is of considerable encouragementthe crews of the various units and injects a competitispirit into the training.d. The listeners are using a delicate sense (the binaursense), and when operating accurately are d:fferentiatibetween the time of arrival of the sound at the left and tlright ears by 1/30,000 of a second. Anything that interferWith their physical and mental well-being, whether worralcohol, or lack of sleep, will be reflected immediately in tlquality of their work . 37. DETERMINATION OF INDIVIDUAL CORRECTIONs.-a. It isthe latter part of section training that the individual corections for each regular and alternate listener are obtaineb. This determination is best made at night. The searclight is placed in action and on the target plane. The Iiteners, blindfolded, track the target. The acoustic-correctoperator functions normally. If the listener has no indVidual correction, the zero-reader needles should rem acentered, as the light is kept on the target plane and tlocator is indicating the direction of the target plane.difference is caused by the idiosyncrasies of the listener athe nonstandard condition of the atmosphere. l!owevc

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~:7-39 COASTARTILLERYIELDMANUALlvhen determinat~ons are made on several nIghts with dif-,ering atmosphenc conditions, an average correction may be:Lrrived at which is usable and which will increase the accu~"acy of the unit. The accuracy of operation may be il1us~j'rated graphically by keeping the target planes' lights onmd pointing the lighted searchlight on locator data.I c. On units having zero readers, this correction can be"ecorded as so many "needle widths" right or left of center.irhe two controllers then use this point, instead of the zeroIlf the zero reader, as the point about which they search. d. On units employing the sound locators, M1A1 and'~lA2, this correction may be applied as an arbitrary correc~~,iondirectly to the acoustic corrector.! e. The operation of the locator acoustic corrector com~:)ination may be tested without the presence of light and::ontrol station. The target plane keeps its lights on. Theocator and corrector are operated normally. If operationIs accurate, target and pantograph pointer will be lined upINith the cross lines in the mirror, providing no parallax::orrection has been applied. The amount they are out ofine is a measurement of the error.;. 38. CHAUFFEURS.-a.The chauffeurs will receive most of;heir training as they move their vehicles from place to place'juring the training of the section.I b. During this training, the chiefs of section will havelmple opportunity to point out the necessary expedients to;he new chauffeurs. The mechanics of how best to driveNhen operating without lights, particularly, how to back upI~or900 feet in order to pick up the blue cable, and how to:;urn around in a restricted space, should all be practiced'1uring this period.I c. The importance of camouflage is pointed out, and prac~.;ice is given in selecting SUitable parking places where nat~'lral camouflage is sufficient. Practice in artiflcially cam-'Juflaging the truck should be given. For more detailed in-;tructions see FM 4-105 and FM 5-20 . 39. OTHERMEMBERs.-The training of the other members)f the section is devoted to fitting the skill they have ac-:Iwred in individual training into the teamwork of the unit.

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ANTlAIItCRAFTEARCHLIGHTNITS 39- 41'l'heir training is not dependent upon an aerial target and~an be carried on almost as well indoors as out and in day-ight as well as dark.II 40. INDOCTRINATIONFPERSONNEL.-'I1lewhole searchlight~~g~nization depends on the accuracy of the soun~ locatorsIIIr Its efficiency. To use the searchlight team at Its maxi-thum effectiveness it is necessary. that all concerned placed eir confidence in the sound locators, and believe that theata sent from the locators are reasonably accurate. 'I1lecrews must also believe that the sound-locator data are~ore a~curate than the guesses made by personnel usingr e U.naIded ear. This: matter is important enough to war-ant a special daylight test or demonstration before theWholebattery. For the demonstration a complete unit is setUP. The listeners and several selected noncommissioned~mcers and privates are blindfolded. A target appears.t Uring the course the searchlight is pointed on sound loca-Or data, and its closeness to the target observed in the~pen sight on the light. At the same time, the unaided;teners stand beside the light and indicate the direction~h the target. The reaction of the rest of the battery toI elr inaccurate efforts to point out the target will usuallytdoctrinate all with the idea that locator data are best.tn the absence of such a demonstration and constant indoc-;Anation by the instructors, the noncommissioned officers5t I tend to revert to the use of their own ears when underress, to the complete confusion of the unit.IItir41. DAYLIGHTPREPARATION.-a.n order to train the cn-h e section to function as a unit prior to working under thet~ndicap of darkness it has been found valuable to trainthe section a few times during daylight. The equipment ofentire section is set up and the listeners are blindfolded.

beie Procedure used is the same as though the training wasju ng carried on at night. The accuracy of the work can be5 dged by looking through the .sights on the searchlight ande~ng how near the target the light is pointed.chi. This set-up gives the battery officers and the sectioners a chance to observe the work of each member of the21

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41- 44 COASTARTILLERYIELD1'.~l'.NUALsection and of the section as a whole. For this trai:'1ing athe sections of a platoon and all platoons of a battery mayassembled at a central location. The sections shculd be seup in a line with an interval of about 10 ~'ards between seejtions. An airplane should fiy courses starting at least 5 mi1~beyond listening range and passing over the line of ligb~on each course. The early courses should be at low altitude(4,000 ft.) and the altitude increased progressively as ultraining of listeners improves until service altitudes of frori12,000 to 18,000 feet are reached.

SECTIONVPLATOON TRAINING

42. SCoPE.-The platoon training should instruct theunits in the teamwork ot operating efficiently with otb'llight units.II 43. PHAsEs.-The training of the platoon can be divideinto two phases, primary and advanced. ,a. The primary training phase affords an opportunity fOthe previously trained light units to work together ining up a single target in the shortest possible time.tice is the most important single factor. Night practicetest. but daytime practice with listeners blindfoldedvaluable.b. The advanced training phase affords an opportunitydrlll the light units in functioning under more difficult serice conditions. Multiple targetn, interference by lowpursuit aviation, functioniilg without communications, aIlfunctioning while being attacked by low fiyingcome under this classification.a 44. NORMALSITUATION.-a. The normal set-up forsearchlight defense is shown in figure 3. Distances 'betwe.lights, and between the advanced listening posts and t~forward lights, will be found in FM: 4-105. The normalmunication net is described in the same manual. Onetery is required to afford all around defense of thetive. The platoon command post is generally located at t~center light in the forward line. Reports come in from t1'.

22

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AIITIAIRCRAFT SEARCHLIGHT UNITS

advanced listening posts through the forward lights to thrlatoon command post. Those reports necessary are reIayeo the gun battery in the defended sector. The platoon com.~ander issues orders and information over the telephonlnes from the command post to the several lights.b. The advanced listening post (observation post) . imanned by an observer (or observers). The only equipmentreqUired is a field telephone.

___ Line Iabll.hed by8allah ....__________ Lin labl,lhed by Gun Baller,___ u lab~",.d b1S.L.BaII...,A Ob valiOll 1'011

FIGURE 3.-Antialrcraft art1l1erydefense of an obJective.

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45 COASTARTILLERYIELDMANUAL 45. SEQUENCEOF EVENTS.-a. (1) It' the searchlight pIa.toon is part of a highly organized defense, it will probabl~secure advance information of the approach of enemy planeS,If not, or if the enemy planes elude detection, the platoon imust depend on its own advanced listening posts. These Iposts, illustrated in figure 3, should give the following dataon the enemy planes heard: J

(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 tbeleft). J(e) Estimated altitude in thousands of feet (altitude 15)',1(I) Direction of travel (north, northeast, east, southeast,

etc,).(g) Time target was heard.(2) A specimen telephone message would read, "Post NO'l2, 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, tbelocation of the target is fairly well fixed.b. Soon after the advanced posts have reported, the firsthum of the advancing planes will be heard at the forward'light positions, when they seem to be at an elevation of'

50 to 150 above horizontal. The sound locators, which have:been previously traversed to the direction reported by tbeadvanced 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 300-45), be'tcommands: IN ACTION. The other pick-up lights in rangego into action immediately and assist the first light to piclt'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 fianks. Those chiefs of section 10"Icated between two targets must exercise judgment as to

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ANTIAIRCRAFT SEARCHLIGHT UNITS 45-47

~hich of the two targets to assign, as otherwise too manyghts will be searching for one target and too few for theother.t d. After pick-up, the nearest two carry (rear) lights placeheir 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,nly a very limited time will be available In which to issue~~der~. Therefore to insure efficient cooperation betweenIIIe lIghts during an attack, the procedure to be followedUst be worked out before the light sections proceed to their;SSigned positions. Initiation of action must be based on aew SImple plans.i b. After the various forms of enemy attack have beenSualized, and sUitable means of combating them have been~vised, the light unit commanders and later the light units&iust be drilled over and over again until their response to aYen situation Is quick and without confusion.e c. The exact procedure to be adopted will depend ondnerny tactics, the prevailing weather, the strength of the&efense, and other factors of the moment. However, certaineneral rules may be laid down.~i 47. NOTES ON QpERATION.-a. All pick-up (forward) lights'W~hln pick-up distance of the target and not needed else-ere w111go into action when the target comes in range.Alb. After pick-up, two carry (rear) lights carry the target.a 1 others go out of action, swing around to the front, andwaJ.t the next target.:blc. If two targets come In simultaneously, two or three()t~k-uP lights search for one target and two or three for theb ere Ifmore than two are heard in a narrow sector,1t 15Uetter to disregard the others and concentrate on pickingP two.dld. Any pick-up light In range whose sound locator orl' stant electric control (D. E. C,) fails should search in theeglon being covered by the other lights.c e. If the distant electric control fails, the extended handantrol should be immediately connected and used.

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COASTARTILLERYIELDMANUAL7- 49j. 'Where no; \"'lire communication between lights

lights always go into action on the initiative of thechief. W'hen one light starts a search, the other pick-lights within range go into action immediately .and assist . 48. MOVI~G SITUATIONS.-a.Whenever the antiaircralartillery defense is acting in a mobile situation, it is necdsary to plan ahead and anticipate the next move. Thisespecially true in situations where no telephone lines habeen laid.b. When the antiaircraft artillery is part of the fieldin combat, it is necessary to have prepared plans for a foward and a retrograde movement. A simple signal from tcommand post searchlight will then direct the movementthe desired direction.c. Roundabout communication can often be securedsending a message via the nearest field artillery telephornet. This is likely to be rather slow if the Field Artilleris busy at the time.d. It will often be necessary to rely on a motorcycle.senger to deliver messages and orders to the variousThe platoon commander should visit each light unit antalk over the situation with the light unit commanders.least once during the day.e. Situations will arise where it is not wise to have tlight units take the road to a central bivouac. In thisit will generally be possible to attach the men of eachto the nearest artillery or infantry unit for rations.j. There. is scarcely any type of military work that makgreater demands on the noncommissioned officer thancommand of an antiaircraft searchlight unit, especially inmoving situation. He must understand something of acoctics, elec.tricity, gasoline motor vehicles, power plants, mreading,'-messing, and supply. The only way the platocommander ~an be sure that the necessary knowledgeacquired is to train the unit commanders and then try theout in simulated war situations.' .n.49. CAR~YINGTHETARGET.-When an illuminatedflies across a defended area, it'must be passed from carlight to carry light, always keeping two lights on it. Tb

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ANTIAIRCRAFT SEARCHLIGHT UNITS 49- 51shoUld be done without orders. In order that all, concernedInay know what is expected, the maneuver should be fre-quently practiced. .Q 50. B01'./IBER FORMATIONS SCREENED BY O~HER AVIATION.-a.'I'he enemy will endeavor to place his low-flying aviationbetween the sound locators and the high-flying bombers.A. Pursuit formation directly inUne with the bombers andclose above the sound locators will' drown out the soundInade by. the bombers, but only momentarily. During' thisInoment when one locator' is blanketed, the other four ofthe platoon are little-interferea with .. --~.

b. When the screening formation flies close to the bomberformation, reliance'must be placed on the difference in soun~between the bombers and the screening planes. Large planesWill seldom if ever be used for screening, as they couldInore efficiently employed to carry bombs. It is unlikely that'the screening formation will be immediately below the bomb-'ers, as they would then b~ in dange.r from the fallingII 51. GLIDING TARGETS.-a. The purpose of gliding in to theObjective is to reduce the noise made by the motors andpro~ellers of the attacking airplane and thereby avoidtectIon. If the light units are located in a very noisy area,or if the light crews are peorly trained, this gives goodSUIts., Against a well-trained crew, these tactiCS,ar,e"almostl

b. During the glide, the motors ~re not turnedofIPrOpellers stopped, but the motors are allowed to idle.".whicbIneans that the propellers will be rotating at a speed of 40reVolutions per minute or more. Each time a blade comesOPPOSitethe wing it creates a characteristic "whosh" whichis easy to identify and center, using the sound locator.t c. Combating glide bombers caIls for greater "alertness onthe part r of the advanced listening posts. They must hear,he gliding airplanes and report to the command post, asotherWise the planes will be over the lights before theirpresence is realized. As these posts are several miles in ad-vance of' the lights, they may be able to hear the planesapproaching before they, statt their glide. . ,

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51-52 COASTARTILLERYIELDMANUALd. Once the locator is "on target," the procedure iJl

searching, picking up, and carrying' is the same as for 8normal target. ,II 52. DAYLIGHTTRAINING.--a. It will rarely be possible toha ve 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 unitcrews. Jb. Advantage should be taken of any nearby commercialair 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 ArmS'and Navy air fields will generally supply a copy of thei!training schedules in advance.c. Failing impromptu air activity, use may be made of

nearby highway or water area where. automobiles or motor"boats furnish moving targets to track.

d. When weather is inclement, the "loudspeaker on 9wire" at the far end of a large garage may be employed. Ifthis is impracticable, the listeners may be drilled on the'binaural trainer. This training may be enlivened byplaying some outside noise such as a nearby electric fan tosimUlate a screen of low flying planes. .

e. During daylight training, the listeners should be blindfolded as the effort to keep the eyes closed is distracting.

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I

CHAPTER 3OPERATION AND FUNCTIONING OF MATERIEL

SECTION I.II.III.IV.V.

ParagraphSound location equipmenL--------------------- 53-5Control station ----- --- 59-6Searchlight------------------------------------- 62-6~~~

SECTIONISOUND LOCATION EQUIPMENT

53. OPERATIONOF SOUNDLOCATOR,M2.-a. This locator hathree composition horns mounted on a pedestal and baserhe acoustic corrector is built into the sound locator. Onorn has been eliminated by using a common horn for botelevation and azimuth. As shown in figure 4, the elevatioand aZimuth listeners stand, one in front of and one in rea

FIGURE 4.-Sound locator, M2, in operating position.21 A . . l' t22' zImuth horn. 24. ElevatIOn. IS ener23' Common (azimuth-elevation) horn. 25. Azimuth lIstener.. Corrector operator. 26. Elevation horn.

235203o~O- - - - 3 29

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53-54 COAST ARTILLERY FIELD MANUALof the locator. They track the target by turning hand-wheels provided. ,b. This locator incorporates several improvements baseupon experience in using the MlAl sound locator. Thehorns have composition walls, so that all noises coming fromthe sides or rear of the horns are deadened and are notheard. The mouths of the horns are rounded, so that thewind does not whistle as it blows across them.c. 'The complete locator weighs 975 pounds (includincase, cable, and reeD and is broken up into six loads, theheaviest of which weighs 350 pounds. It can therefore bcarried 'in the body of any truck and can be manhandledinto any operating position desired.

d. Several steps must be taken before the locator is readto furnish data to the searchlight.(1) The locator must be assembled in its operating posi

tion, leveled, and connected by cable to the searchlight adescribed in paragraph 88.(2) It must be oriented and synchronized with the con-trol station and the searchlight as described in paragraphs96 to 99, inclusive.(3) Itmust, be prepared to track the target as describein paragraph 55. 54. OPERATION OF ACOUSTIC CORRECTOR ON SOUND LoCATOR,M2.-This corrector is an integral part of the M2 sounlocator and requires one operator.

a. Wind corrections.-The corrector, illustrated in6 and 7, has provisions for incorporating corrections foparallax. The correction for wind effect, parallel to thetarget's course, is automatically taken care of when the aispeed of the target is set in, and that at right angles to thetarget's course is disregarded.

b. Parallax corrections.-Parallax corrections are maderotating the parallax cam. This earn is graduated in reference numbers from 0 to 10. ,The proper correction to bapplied is determined in figure 5. For example, when usina 900-foot base line between the sound locator and search-light, if the estimated slant range to the searchlight pick-uis 18,000feet, the parallax offset should be 4 on the paraIla"scale as shown by the intersection of the dotted'line With900-foot base line. These corrections are set in before track-

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ANTIAIRCRAFT SEARCHLIGHT UNITS .( 54-55

ing is begun. During tracking, the acoustic-corrector oper-~or keeps the pantograph pointer 11), fig. 6) centered in, e cross at (12) by looking through the peep sight. He~cCompushesthis by turning the correction handle 34),g. 26) for azimuth control and by rotating the correction

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COAST ARTILLERY FIELD MANUAL

d. The listeners will, in the meantime, don their helmet;and adjust the straps to provide for maximum soundproof.I ness compatible with comfort as follows: Adjust the chi) strap and head ties until the ear cups (the large paddeli cups which surround the entire ear) fit snugly against thhead and the earpieces are alined with the bore of the ea canal. In this position the ear pieces will surround the tragu(fleshy part) of the ears but will not bend the tragus S

I that it. blocks the passage from the earpieces to the e}canal. Screw the earpieces into the helmet until they reI firmly but comfortably against the ears.I e. When the helmets are properly adjusted, the listeneI24) and (25), fig. 4) will step onto the platform and

I their respective tube ends into their earpieces. The sounlocator is now ready for operation.

1

FIGURE 5.-Corrector operator in action.1. MUltiplying pantograph. 10. Target air speed scale.2. Target air speed setting 11. Pantograph pointer.knob. 12. Sight mirror cross lines.7. Pantograph attaching stud 13. Level.knob. 14. Elevation clamp.8. Parallax earn. 15. Parallax scale.9. Declutching gear.

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ANTIAIRCRAFT SEARCHLIGHT UNITS 55-

FIGURE 7.--Acoustic corrector, sound locator, M2.1. Pantograph. 4. Mirror.2. Pantograph pOin:er. 5. Mirror cross lines.3. Sight .

56. TRACKING THE TARGET.-a. To aid the listeners to picUp the target, the push button switch ((31), fig. 26) may bPUshed in, thereby decreasing the A. C. hum of the dattransmitters. As soon as the location of the target is clearlestablished, release the switch. DO NOT track with thiSWitch pushed in.b. The corrector operator will move the correction handland knob (34) in such a manner as to keep the image of thPantograph pointer continuously on the cross lines of thlllirror.

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I

.) COAST ARTILLERY FIELD MANUAL

I c. The listeners will rotate their respective handwheels to'laintain a binaural balance on the sound source. Thelandwheels are turned toward the ear in which the soundredominates to achieve binaural ba.Iance., CAUTION: In the operation of the sound locator the lis-;mers should be cautioned against making sudden changes'l the rotation of the handwheels. Such jerky operationill cause the end of the pantograph to move back and forth'I the field of view of the corrector sight, thereby making it:npossible for the corrector operator to apply the properI)rrections to the transmitted data. The listeners shouldI~ trained to track smoothly by getting into the habit ofltating the handwheel continuously, even though they hearIle target. intermittently. If the listener should detect thatis lagging behind the target slightly he should accelerate

lis handwheel rotation speed slowly until the target is again'~ntered. Likewise, he should retard his handwheel rotation'{a slight amount.if he finds he is leading the target. Suchilomentary deviations from true centering are not harmfulI; they serve to sweep the beam over a small area in thecinity of the target, thereby assist~ng the search for theiLrget in a controlled manner. Jerky tracking is a far moreI~riousfault than slight inaccuracies in centering which are,:adually corrected.: d. The corrector operator must recognize that the panto-.'aph pointer does not oscillate or move in jerky fashionhen the listeners follow the target perfectly. Therefore,hen jerky operation of the pointer occurs, he should realizeat it is due to the listeners and he will not attempt to followLpid movements of the pointer but will endeavor to average'It such irregularities, so that the correction he inserts willsmooth and uniform.e. It is emphasized here that the acoustic corrector opera-lr should be trained to develop judgment in following thelntograph pointer in his sight, rather than in the merelechanical performance of his work. By his delicate touch:= must smooth out the jerky variations introduced by the'ackers as they strive to keep the sound centered. In gen-...al, the operator should endeavor to keep the pantograph,)inter within the circle inclosing the cross lines (02), fig. 6).

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ANTIAIRCRAFTEARCHLIGHTUNITS 57 57. OPERATIONOF SOUND LOCATOR,MIAl.-a. This locator(SOmetimes called the longhorn) has four metal hornslnounted on a four-wheel trailer. As shown in figure 8, foureXPonential horns are mounted in trunnions that arelnounted on a turntable. One pair of horns (the upper andlOWer) determines the elevation of the sound, the other pairthe aZimuth. The pointing of these horns in azimuth andelevation is transmitted mechanically to the acoustic cor-rector which is mounted on one end of the trailer.

FIGURE 8.-Sound locator, MIAIcorrector. 14. Turntable locking screws.15. Horn locking brace (removed).16. Traveling horn supports.17. Hand clamp nuts.18. Horn support yo~e.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.

1. Acoustic2. Jacks3 .4' lIFront seat (removed).5' orns.6' raversing handwheel.7' levating handwheel.8' lIeadset (azimuth).9' lIeadset (elevation).10' lIo.rn journal bearings.11' AZImuth scale.12' 'I'urntable.la ' ~eats for operators.. Ootrest.

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;57-58 CO.\ST ARTILLERY FIELD MANUALb. 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 develoPjudgment in their listening and centering. In following a,moving target, the handwheel should be kept moving at ll.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 by the chief of sectionis set in by turning the altitude setting knob 1), fig. 9).

FIGURE 9.-Acoustic corrector, M1.scale and setting 10. Plug receptacle.11. Outer predictor scale pointerSand cperating knobs.12. Inner predictor scale pOinterS

and operating knobs anoclutch operating buttonS13. Sound lag drum and chart.14. Spotting correction knob.azimuth.15. Spotting correction knob,elevation.17. Data transmitter. azlmutb.18. Data transmitter, elevatioIl'36

1. Altitudeknob.2. Corrected azimuth scale andreleasing knob.3. Corrected elevation scale andreleasing knob.4. Differential gears.6. Lamp.7. Lamp switch.8. Predicting mechanism andscale, azimuth prediction.9. Predicting mechanism andscale, elevation prediction.


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ANTIAIRCRAFT SEARCHLIGHT UNITS 5

b. For this acoustic corrector two operators are requireone of whom must be equipped with a stop watch. Thlength of the interval during which a correction is to bComputedis indicated by the pointer at the sound lag dru(13). The command is given: 1. READY, 2. TAKE, anthe watch is started. At the expiration of the indicatetime, the operator gives: 1. READY, 2. HALT.c. Each operator insures that the prediction-scale pointeinner, is set at zero before a prediction operation is begu.At the command TAKE, the operators apply a slight pressurWith thumb or finger to the button (2) at the center of thSCale. At the command HALT, the pressure is released. Thoperator then brings up the outer-matching pointer (1) tthe pOsition on the scale indicated by the inner pointer (2)This operation should be performed, as nearly as possiblSimultaneously with the movement of the inner pointer.soon as the pointers have been matched, the inner pointe(12) is reset to zero and the operation is repeated.

d. The outer pointer (11) actuates the frame of the trans1l1itterand thus sends the corrected data to the comparatoTherefore it should not be returned to zero, as a correctioonce inserted should remain until another is determined an~ntroduced. Experience on the part of the operators wiIndicate to them when an erroneous prediction has bee1l1ade,in which case the former one is left in the systeUntil the proper correction is determined by a subsequeoperation.e. Atmospheric, wind, and arbitrary corrections can badded to the readings at the transmitters by turning off thamount of the correction on the spotting dials (14) an


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:'3-60 COAST ARTILLERY FIELD MANUALIletermination and application of corrections. They should',:now that the corrections determined will actually change'1:~raduallY,nd that any radically different corrections should,[Ilotbe applied to the corrector. The operators must "smooth,'Iut" the corrections before applying them, insuring an evenI:lowof data to the control station. It is emphasized again'Ihat the training of these operators must develop judgment'ather than a mere mechanical skill in the operation of the'Instrument.

SECTIONICONTROL STATION

I 59. FuNCTION.-The control station is the device that'~nablesthe searchlight to be controlled from a distance, and',:0 be directed at the point in the sky indicated by the sound''~ocatoras the target's position. In addition, it enables the~:earchlight to search the sky in the immediate vicinity of'he point indicated bY'the locator. This is accomplished byInanipuIating the handwheels at the control station so as:0 move the light up and down and right and left from the;ndicated point.~I60. MECHANISM.-Thesearching mechanisms on control::tations have undergone an evolution which has brought'hem back to the place they started in the first units":~quippedwith distant electric control. At this time the'::earch was wholly manual, being accomplished by manipu~lating the controls on the distant electric control system back~Ivard and forward and up and down in order to obtain the.Ilesired searching pattern in the sky. On the M1934 control,itation a mechanically operated spiral searching device:ldded. On the M1937 control station this was changed toJrovide for an automatic electrical searching device in eleva~':;ion only, the search in azimuth being accomplished man~lally. On the M1939 unit all automatic searching devicesIlave been elimi'nated, and the search is accomplishedlally as on the MVI unit. All control stations havingnatic searching devices were prOVided With means for;hrowing these automatic mechanisms out of gear and re~

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ANTIAIRCRAFTEARCHLIGHTNITS ,.; 60-61Verting to manual operation. On the M1934 and all laterControl stations, a pair of binoculars (or night glasses) wasI.roVided to aid in the search. These glasses are auto-1l1aticallydirected o'n the point in the sky at which the. searchlight is pointed. With the aid of the glasses it hasI~rovell possible to pick up targets which have been buttt ghtly fiicked, or when they have been dimly illuminated by.;e searchlight beam passing nearby in hunting the target.f in some types of aircraft it has been possible ~o make at P Ck-up using the glasses alone as the glow of the exhaustf cOUldbe seen..61. OPERATIONF CONTROLTATION,M1939.-a. On thist :ntrol station (fig. 10) there are three operators-an azi-uth controller,' an elevation controller, and the searchlight~~nunander (acting as control station chief> who lookstOUgh the binoculars. The azimuth and elevation con-d.rOlIersause the searchlight to be set on the sound locators:ta by centering the zero reader pointers at the control:rnati?n, and conduct the search by slowly and smoothlyampulating the azimuth and elevation handwheels located~n the sides of the control station. "As they search, theh~archlight commander observes that part of the sky througha~Sbinoculars. If the sound locator is being properly oper-s ed it should place the beam within 50 of the target. Theearchers operate the controls to cover this 50 "area of~rror." As soon as the target is picked up, the searchlighte~nunander takes over completely from the azimuth andbevation controllers, keeping the light directly on the targetr:. lnovement of his handwheeJs .. While tracking the illu-Sl~natedtarget, the searchlight commander keeps it on the() e of the searchlight beam nearest the gun battery, so thatt~erators at the gun battery do not have to see the targetrOugh the searchlight beam.

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83. Leveling jack.103. Elevation observer's hand-wheel.106. Elevation h and w he e Iclutch adjuster.112. Binocular mount clutchadjuster., 114. Elevation zero search indi-cator.122. Azimuth observer's hand-wheel.124. Azimuth zero reader hand-wheel.125. Azimuth h and w he e Iclutch adjuster.131. Binocular mount azimuthslip adjuster.

132. Azimuth zero reader.134. Search knob.

141131

134

147

4'9

-------- 418

417

-----.-106

------342

219

FIGURE10.-Control station.139. Signal buzzer push buttol)141. Binocular mount adjusterhandles.142. Carrying handles.143. Binocular elevationmarker.144. Binocular azimuthmarker.147. Tripod.156. Dial light switch.160. Binocular mount counter219. Handhole cover plate.220. Binocular height adjustiIlgknob.315. Alinement lug.342. D. E. C. switch.417. Binocular mount.418. Open sight.419. Fifteen point receptacle.

zer

zer


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ANTIAIRCRAFT SEARCHLIGHT UNITS 6b. The three men composing the control station ere

shoUldbe trained together as a team, as the successful operation of the station depends on an instinctive cooperatioamong all three. The azimuth controller must keep thZeroreader needle on or in the vicinity of the zero point b!nust also search in azimuth. If the target is not picked u. in a few seconds, the controller must insure that the ligbe again pointed on sound locator data by seeing thatZeroreader needle is exactly zeroed. The elevation controllhandles his controls in a similar manner. At the cornmanFLICK, given as the light beam passes over the target, tsearchlight commander takes over complete charge of thControls and keeps the light directed on the target.c. The sequence of events at the control station onnormal course occurs as follows:(1) 'The sound locator operators will report on target, an

the moving of the zero reader needles will indicate that datare coming through. This report will generally be giveWhen the target is about 100 to 200 above the horizontal'elevation.(2) The azimuth and elevation controllers center the zereader needles, thereby pointing the darkened searchligon sound locator data.(3) At the command IN ACTION (generally given whethe target is about 300 to 450 above horizontal in elevationthe searchlight is lighted, and the two controllers at the cotrol station immediately commence their search.(4) The target will next be momentarily illuminate(flicked) by one of the lights in action. When this is noticby the chief of section or No.4, they report FLICK to t~earchlight commander. When the searchlight commandIS ready to take over the operation of the control statiofrom the controllers, he commands: FLICK, takes over tControls,and tracks the tanz:et.(5) At the command OUT OF ACTION, the lig~t is put oubut all elements of the unit continue to track the' targe(6) At the command CHANGE TARGET, the controllers centthe zero reader pointers, thereby pointing the light in t

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I

Ilrection indicated by the sound locator. Search isI:lencedfor the new target in the usual manner.

:L-63 COASTARTILLERYIELDMANUAL

SECTIONIISEARCHLIGHT

Icom-

I: 62. OPERAToR.-Thesearchlight operator must be trained"l the functioning of the searchlight itself. His. post is atIlle light during operation. Due to the number of auto- JIlatic devices provided, the searchlight operator has little:) do during normal operation. He should be thoroughly:tmiliar with the manual operation of all the automatic:~vices and fully capable of operating them efficiently when::tlled upon.:, 63. NORMALOPERATION.-a.During normal operation, theIllarchlight operator assists in unloading the light, setting it::p and leveling it, and connecting the cables.I, b. He assists in orienting by pointing the light as directedI:sing the orienting sight. After the light and locator are 01roperly pointed, he centers the zero-reader meters by turn-.:lg.the knob on tile azimuth and elevation receivers (for,~tails as to orienting the unit see pars. 97 and 99).I c. At the command IN ACTIONe closes the arc switch on:le light, thereby striking the arc. At OUTOF ACTIONepens the arc switch.! d. After about 45 minutes of continuous operation (or:hen the positive carbon is half used) the operator recar-'emsthe light, replacing the old carbons with a new positive:rid new negative carbon at the first break in operation.:he new positive carbon should always have a crater previ-:usly formed by a few minutes of operation at the bivouac'r garage.: e. The operato,r constantly checks his ammeter and volt-;leter to see that the searchlight is operating on correct:urrent 045-150 amperes) and voltage (78 volts). He also'necks the appearance of the arc as seen in the ground glass:iew finder, keeping the positive crater even with the ref-'rence line on the view finder.

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ANTIAIRCRAFTEARCHLIGHTNITS 63- 65f. Adjustment of the arc length should only be undertaken

Under the supervision of the chief of section. The length is~djusted by turning the arc length adjusting screw shownIn the lower right corner of the lamp mechanism box 27).fig. 11); the greater the arc length, the greater the voltageacross the arc.9. The thermostat control system should only be adjustedUnder the supervision of one of the battery electrical ser-~eants or of the chief of section. Directions, will be foundIn the instruction book.II 64. LEVELINGHELIGHT.-The light is first lifted off theground by means of its. four leveling jacks 83), fig. 21)and approximately leveled. The light is traversed SOl thatone level tube is parallel with the frame of the chassis; theother will be at right angles to it. Using the leveling jacks,~helight is leveled so that the bubbles are centered in theirUbes. The light is then traversed 3,200 mils eratorshould enter the, light on the side away from the.,hermostat. He should wear gloves and should have on some.~ort.of clothing so that his arms, shoulders, or body will notcaIne in direct contact with hot metallic parts. The main~rc SWitch should be "off." If at night, the reearboningIght should be turned on. .thb. .uSing the recarboning wrench, the operator forces apart1 e Jaws that grip the positive carbon, and the carbOn stub; Withdrawn to the front. 'A new positive carbOn ((15)g. 11) with a crater already formed by a few minutes of~l>erationis inserted from the front and the wrench ~s re-oved, allowing the jaws to grip the carbon.


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t

65- 67 COAST ARTILLERY FIELD MANUALtive 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

F~%~'c. To recarbon the negative head, the operator pullson the negative-release lever, thereby releasing the old nega':tive carbon, which is removed. A new negative carbon (1) isinserted so as to project 1 inch beyond the negativeand the negative-release lever is released allowing the neg;ative mechanism to grip the carbon. 66. MANUAL OPERATION.--a.' Whenever an automaticfails, it is necessary to change to manual operation. Tbe'operator should be drilled constantly on changing over to 'manual operation so that he will be ready if a failure

b. (1) When the automatic positive feedfails, it is possible to change to semiautomatic feed usin(the semiautomatitc feed-rate adjusting knob 6), fig. IV:By moving the knob farther to the left it is possible tothe motor feed the positive' carbon forward at a rateto the rate of burning. ,I(2) Full manual control may be exercised by turning Wepositive hand feed (22). ,, c. The negative feed may be hand-controlled by shiftill

I th, negative feed centralizer knob (12) from "auto""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 observingI 'in' the ground 1 glass view finder and keeping eachon its proper ~~ne.,:".,I 67. MANUAL DIRECTION.-a. In case the distant electricI, trol fails, it is possible to direct the searchlight: either by moving the light itself or by means of the;,tended hand control. '::; b. By observing the zero reader dials, it is possible'I direct the light manually using sound locator data.:1 c. If no .sound locator data are available, it is best to, nect the extended hand control and direct the light from'I end of its handle.

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head,

devic

occur


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ANTIAIRCRAFT SEARCHLIGHT UNITS

FIGURE n.-Lamp and lamp-control mechanism.

67

. .1

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68- 70 COASTARTILLERYIELDMANUALSECTIONIV

POWER PLANT 68. STARTINGOWERPLANT.-The operation of startingpractically the same as that of starting a car.a. Put main switch 20), fig. 12) and voltmeter andcircuit 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 switchpress in the starter button (12), and adjust choke (9),required for smooth operation. After the engine h;twarmed up sufficiently and after operating smoothly aminutes, push choke (9) back in, and pull out throttle COIltrol to wide open position. Tachometer (6) should indicat6approximately 900 revolutions per minute. 69. LISTENINGLOADVOLTAGEADJUSTMENT.-a. Close tbvoltmeter and lamp circuit breaker (


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ANTIAIRCRAFT SEARCHLIGHT UNITS 70

arc current. The instruments on the control panelshoUld indicate approximately the following:

Ammeter (3)Voltmeter (4) ------------------.-----------Tachometer (6)Oi l gage ( 7 ) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Temperatur0 gage (8)

(fig. 12)165100

1, 20015- 20

160- 200

panel (front view),U. Throttle .12. starter button.13. US-volt lamp receptacle.14. lIS-volt light switch.] 5. Fan season switch.16. Ignition switch.17. 6-volt light switch.18. 6-volt receptacle.19. Power voltmeter and lampcircuit breaker.20. Main switch.

FIGURE12.-Control~. A~c load voltage rheostat.. Listening load, voltage rheo-3 stat.4' PO\\er ammeter.S' Power voltmeter.6' Charging ammeter., Ta.Chometer and revolution7 .counter.8' ~1l pressure gage.9' Cemperature gage.10' hOke., Gas gage.70. ARC LOAD VOLTACFJ An.HTSTMENT.* * * * * *~l'~:l'he power plant * The engine automatically in-i .. li';es speed to 1 200 revolutions pel' minute when the arc load

'\ .\\'!I'DDlied, and decreases to 875-900 revolutions per minnte1 ell the arc load is removed. Arc load * * * for tem-ler'lt. lIre variations.[A. G. 0(;2.11 (5-2-41).] (C 1, July 15, 1041.)

_----------------------------

_

'" '"~ '


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7ll-73 COAST ARTILLERY FIELD MANUALArc load rheostat (1) when once set should not need to beadjusted except to compensate for temperature. 71. MANUALCONTROL.-a. The voltage and speed may becontroled manually should the governor fail or manual conjtrol be desired. Jb. It is necessary to block the governor arm in forwar.position in order to prevent interference from the mechanic~r~nvpr nnr . .c. With throttle 11), fig. 12) set at listening speed (r. p. m.), the arc should be struck and at the samethrottle adjusted to obtain the correct arc load speed of 1,jrevolutions per minute. Satisfactory * 1\ 0 * in paragr70. * * * * * * *[A. ? ~G2.1l (5-2-41).1 (C 1, July 15, 1941.)

removal oj arc load to decrease engine speed to 900tions per minute. This must be done to avoidengine and excessively high voltage.d. If the engine speed adjustments are carefully made,will be unnecessary to change settings of listening loarheostat (2) or arc load rheostat (1) when changingone speed to another. ,Ie. If any part of the governor 0'11 its control mechanisJfails, it is necessary to wire open the valve leverthe butterfly valve in the valve box assembly. This wiallow the engine speed to be controlled by the throttle. 72. STOPPINGPOWERPLANT.-To stop the engine after tb'arc load has been removed, open the main switch 20), fi12) and turn the ignition switch (16) "off." Open themeter and lamp circuit breaker (19).NOTE.-The main switch (20) should always be opened to avo

st.rtblg connected load ~::;:: 'j'.' 73. SEARCHLIGHTVEHICLEs.-Searchlight vehicles ha'changed considerably. The first modern unit, the MVI, we.

48

variationS,

time.:

revoll1

overspeedin

frori

control1in

volt


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I

ANTIAIRCRAFT SEARCHLIGHT UNITS 73-74carried by a combined truck-power plant (fig. 13) whichtawed 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})OWerunits. Subsequent units, the M1937 and M1939,Used two cargo trucks with each searchlight unit. The~1940 unit employs two trucks of special design. (See figs.I 6 and 17,)II 74. MVI POWER UNIT (figs. 13 and 14).-a. Description.-~escription of the automotive features will not be included1n this manual. A 15-kilowatt, l50-ampere, 100-volt, 1,800~eVolutionsper minute, compound generator is mounted onhe drive shaft of the motor with provision for engaging eitherihe generator for supplying the searchlight or the tail shaftOrlocomotion. The generator clutch shifting lever is locatedOn the left of the driver's seat. A governor is provided toia~ntain an engine speed of 1,800 revolutions per minute.fh1Sgovernor may be disengaged when traveling by meansthe governor cut out control on the dash. A %-kilowatt,25-volt rotary converter, supplied by the main D. C. gen-

~rator, furnishes the alternating current for the compara-})or. I~ is located on the right running board. A controlanel 15located in the driver's cab in rear of the seat. It~Ontains two main circuit breakers, D. C. ammeter andJ\Oltrneter,generator field rheostat, rotary converter switch,c' C. voltmeter, and illuminating lamp. The truck bodysOntains a loading winch with cable and ramps, boxes forteCUringcomparator, comparator and controller cables, andWoreels for the main power cables.r b. Operation. (1) Traveling. Before starting on theoad, check for the following conditions:g (a) Governor control should be out (governor disen-aged).

1 (b) Generator clutch lever (left of driver) should beoCkedforward by means of the chain provided:'(c) Generator ventilating doors should be clamped shut.

'e b (d) The searchlight chassis should be locked in positionI~ 'Y the three clamping, devices.

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74 COAST ARTILLERY FIELD MANUAL

1. Rotary converter.2. D. C and A C. cable recepta-cles.3. Power cable reels.4. Controller and comparatorcable storage boxes.

FIGURE 13.-MVI searchlight and power unit, traveling positiOJ(paulin removed) .. 5. Controller and comparato'tripod.6. Container for spare carbopS7. Controller storage box.8. Comparator storage box.9. Loading winch axle.

(e) The aZimuth lock of the searchlight must be locke'in its correct riding position.(j) The steady bar should be locked in place.(g) The elevation clamp on the trunnion, the elevatiO

clutch, and the azimuth clutch should be released.(h) The circuit breakers and switch on the control pape

should be open and the sliding doors closed.(2) Unloading and connecting searchlight (fig. 14) .-ca

Release canvas cover and raise bows about 3 inches in tbejlsockets.

(b) Place ramps; secure with pins.(c) Remove reel boxes and extended hand control.(d) Release devices which secure searchlight to truelboos.(e) Attach steering handle and loading winch cable.

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ANTIAIRCRAFT SEARCHLIGHT UNITS 74(/) ..Attach cable reel handles on each side of loadingWinch, raise pawl from ratchet, and, with one man on each~rank and one man guiding the tongue, alloW searchlighto roll slowly down the ramp. .(g) Unreel the main power cables and attach plugs to the3Tellowreceptacle on the power unit and searchlight, being;arefUI to see that the guides on the plugs are properly~ltted.

(h) Interconnect all other cable~ between ~ound locator,~OInlJarator, distant electric' control, and searchlight accord-ng to the color scheme of the plugs and receptacles.(3) Generation of power.-(a) Open ventilation ports ofgenerator and start engine. - : - '(b) With. engine idling, shift generator clutch lever (leftO~driver) to the rear, engaging the generator. to the drive~haft. If gears will not mesh, it will be necessary to depresse engine clutch, shift the transmission to low gear, andgently release the engine clutch until the generator can beengaged. The transmission should' then be returned to theneutral position. . .(c) Engage governor; depress engine clutch and put gearShift lever in high gear; release engine clutch carefully.(d) Open throttle wide and advance the spark. ,. (Speed-OIneter should read approximately 25 miles per hour,) .!

t (e) Reg~late field rheostat to bring direct current voltageo 100 volts. ' '. /' .b (1) When the engine has .warmed up, close the circuit......eakers and start the rotary converter by closing the doubleI ~le knife switch on tb,e power panel.' '.1n (g) .When the arc is struck, the following readings of theeters should obtain: . 'Volts Amperes .

Searchlight operating alone_____ 100 150: .., Searchlight. and comparator_--~- 100 . 157' .Searchlight, comparator, and COl1- ,,", 1751troller 7~ ~_~ 100

It

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-


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74-75

1_______2.345


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.4:. Locking pins for searchlight.5. Loading winch with cablewound properly.6. Coupling.7. Carbon container.

8. Tripod. dfl. Cable reel cranks in loadeposition.10. Pins for locking rear seat.11. Turnbuckle for 10 c k i pgsearchlightl ati 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 vo~ts to obtain the propelarc current. This is due to the increase in resistance of Wecables as they become heated . 75. M1934 POWER UNIT (fig. 15) .-This power unit issimilar to the power unit MVI (par. 74) except that ita more powerful motor. It has a generator and sWiteb'board equipment designed to supply current for 150-ampere,200-ampere, or 250.-ampere operation of the searchligbt,The unit is designed to run at two engine speeds, a(quiet) speed for the listening load and a 1,100 to 1,40revolutions per minute operating speed. The unit automati'

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ANTIAIRCRAFT SEARCHLIGHT UNITS 75- 77~ally speeds up as the arc is struck and the heavier current13 needed.

FIGURE 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 extraeqUipment. Two trucks were required per unit; almost any~argo truck of sufficient carrying capacity and large enoughOdy could be used.b. A block and tackle was furnished for pulling light and~~we~ plant into the truck; ramps for each truck allowed

b e lIght and power plant to be drawn up into the truckf dy; some form of hold-down device kept the equipment1'1'Olllshifting when the truck was in motion. The creode Where they could in the truck cabs and bodies.w.77. M1940 VEHICLE (fig. 16) .-The vehicles furnishedc Ith the M1940 units are special vehicles. They are of the:-over-engine type and drive through four rear wheels.

'ce special double cabs (fig. 17) accommodate the entire1'ewof the searchlight unit.

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FIGURE 16.-Truck, M1940 searchlight.

FIGURE 17.-Gab, M1940 searchlight truck.

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CHAPTER 4PREPARATIONS FOR ACTION AND FOR MoVEMENT

. ." ParagraphSECTION I. Preparing for action ..:________________ 78- 9. II. Orienting and synchronizing________________ 95- 9 ,

III. Preparing for the road 100-10IV. Protective measures 109-11SECTIONI

PREPARING FOR ACTION 78. ScoPE.-This section describes the setting up of thequipment from traveling position on the road to operatinllosition ready for action. .,' '.. 79. TRAV~LINGOSITION.--a. When on the road,' one com:Plete searchlight unit uses two trucks-the first carryin~he searchlight, control station, and the sound locator; anhe second truck the power plant and the cables. .t b. The personnel and equipment are in places on thrUcks as indicated in figure 18.80. SELECTIONOFSEARCHLIGHTOSITION.-The position seected should be- .t a. On or near a road good enough to permit use by th

trucks in all. kinds of weather. (In terrain permittinrUcks to move cross country in all kinds of weather, thi:PrOVision

military searchlights (1943)

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