The use of searchlights for flashing-light signaling purposes, both day and night, is so general throughout the service that the Signalman must have a basic knowledge of the operation of this type of signal apparatus. An intelligent understanding of the proper operation of the various types of searchlights will do away with unnecessary trouble, delay, expense, and inconvenience.

Searchlights and their accessories constitute material under the cognizance of the Bureau of Ships, and the Engineer Officer of a vessel is directly responsible for the material in accordance with existing instructions. This does not in any way relieve the Signalman of the full responsibility of observing the instructions for the proper use of this type of material. The instructions set forth in this chapter are meant to serve as a general guide and are not to be taken as altering the operating instructions in effect on any vessel.

Many ships have found it satisfactory to assign the upkeep of signaling apparatus as one signalman's cleaning station. He is required to check and clean the gear daily, thus preventing the run-down condition which otherwise would ruin the shutter assembly and delicate spare parts of signal searchlights. Operating a light with loose or missing screws in the shutter will cause the blades to crack and break easily. Salt spray on the lens and reflector not only reduces the operating range but in time pits the reflector. A piece of leather or sponge rubber secured to the arm stop will reduce shutter vibration. If operators will realize that the life of a signal searchlight is directly proportional to the upkeep they give it, the situation will take care of itself.

In general, searchlights may be classified as incandescent and arc types.

12-INCH SEARCHLIGHT

In this type the source of light is a specially designed incandescent lamp. Control of the light is by means of a shutter arrangement. The front and rear doors are hinged to the searchlight case to permit access to the interior for relamping and cleaning. There is usually a handle on the rear of the case to elevate and depress the light or turn it in azimuth. Relamping and refocusing should be done only by the Electrician's Mate in charge of searchlights, unless a member of the signalman gang is qualified and authorized to do so.

OPERATION

The Navy standard 12-inch searchlight is simple to operate. Any striker can learn in a short time the proper procedure for turning the lamp on and off, positioning it horizontally or vertically, and operating the shutters.

INSPECTION AND MAINTENANCE

In general, Navy searchlights must be maintained in accordance with the same good practice which relates to all electrical and mechanical equipment. Specifically, (1) electrical contacts must be kept clean and bright to maintain good contact; (2) all moving parts must be lubricated at intervals dependent on the severity of service; (3) the trunnion bearing and stanchion socket should be lubricated with light grease in the fittings provided; and (4) screws and bolts should be checked for tightness at regular intervals, particularly following firing of the vessel's guns.

The shutter vane hinges and links are lubricated at the factory. They should be relubricated once a month or at intervals as required with graphite mixed with kerosene to float it into place. This mixture should be used sparingly to prevent spattering on the door glass and reflector. It is recommended that the searchlight be operated for a few

minutes after relubrication with the door glass and cover removed to allow the kerosene to evaporate.

At regular intervals the two shutter-stop screws should be adjusted to take up wear in the leather bumper. The leather bumper should just touch the stop adjustment when the vanes are closed, so as to prevent twisting of the shaft.

Figure 2-9.-12-inch Navy searchlight.

The reflector should be cleaned weekly or oftener to remove all the dust. The reflecting surface should be polished with any standard Navy brightwork metal polish on absorbent cotton or a soft cloth.

Do not clean the reflector while it is hot. Never use polish containing iron or abrasives. Do not wipe the reflector with a rotary motion but pass the cotton or soft cloth over the surface of the reflector in a radial motion from the center toward the rim of the reflector.

CAUTION

No incandescent lamp should be kept burning for a longer period of time than is absolutely necessary to do the required job. Incandescent searchlights should not be used for general ship illumination unless by authority of the Commanding Officer.

When the searchlight is used at night, the beam should be projected where it will be most clearly distinguished by the receiving unit(s) but not directly on the receiver. Great care must be exercised to see that the searchlight beam is never turned on the bridge of other vessels.

During daylight the searchlight must be accurately trained on the receiver. For this purpose searchlights are fitted with a sighting device. This device is generally found on the righthand side of the barrel.

The ship's specific operating instructions for searchlights should be studied and understood before attempting to operate or cut in any searchlight. The following operations are general:

TO START.-Turn main switch handle to ON position.

TO STOP.-Turn off the above in the inverse order of turning on.

TO TRAIN.-Unlock the clamp and turn the searchlight by hand.

TO ELEVATE AND DEPRESS.-Unlock clamps and elevate or depress the searchlight by hand.

24-INCH SEARCHLIGHT

The carbon-arc 24-inch searchlight is intended primarily for signaling and secondarily for navigational use. It consists of a stationary pedestal which is secured to the searchlight platform, a turntable which carries the two trunnion arms and rotates in train on the pedestal, and a drum which is pivoted on the trunnion arms to allow it to be elevated and depressed.

The drum contains an automatic high-intensity carbon-arc lamp which is operated from a direct current power supply. At the rear of the drum is a metal reflector. At the front of the drum is a dome glass, an iris shutter for shutting off the searchlight beam completely, and a high-speed sector vane shutter which may be operated locally or remotely for signaling with the searchlight beam.

Handles at the rear of the drum provide a means of swinging the searchlight in train and elevation to direct the beam

of light. The drum may be rotated continuously in train and between angles of 110-degree elevation and 30-degree depression.

Figure 2-10.-Standard 24-inch Navy searchlight.

When the searchlight is in proper working condition and the carbons are properly installed, the modern automatic searchlight requires very little attention while operating. However, great care should be exercised not to permit the carbons to burn beyond the safety limit, which would cause the noses of the carbon heads to be damaged or completely melted. This can be prevented by frequently observing the position of the carbon tips through the smoked-glass lenses provided for that purpose on each searchlight case. All arctype searchlights have peep sights so that the operator can check the carbons.

OPERATION

In general, except in an emergency, a large searchlight should not be turned on until permission has been obtained from the Officer of the Deck. The main reason for this is that the searchlights draw a large amount of power, and the engine room should have an opportunity to prepare the generators to take the load. On destroyers the unexpected