ML-121 CEILING LIGHT PROJECTOR

so adding the correction is acceptable. At 2334Z, we read the left side of the solid band at 33°. Adding the equipment correction of 2° would result in only a 35° corrected angle. Since the correction is less than 45°, the correction is not added, and the 33° elevation angle should be used. CONVERTING ELEVATION ANGLE TO CLOUD HEIGHT.—The operator’s manual for the GIFFT recorder contains a table for converting elevation angle to cloud height for units using the standard 400-foot baseline. A table may be constructed for your unit’s baseline, if different from the standard, by multiplying the tangent of the elevation angles from 1° through 89° by the length of your baseline, in feet. Maintenance Maintenance requirements for the RO-546 recorder are described in the operator’s manual. All calibrations and electrical checks are performed by base ground electronics personnel. Aerographer’s Mates are responsible for changing the recorder chart paper and replacing the chart-marking stylus when the old stylus becomes worn, broken, or bent. Pilot-reported cloud heights that are consistently different from RO-546 indicated heights, or other indications of malfunction, should be reported to ground electronics. Backup equipment, such as the ML-121 ceiling light projector and the ML-l19 clinometer, should be used when the AN/GMQ-13 is out of service. ML-121 CEILING LIGHT PROJECTOR The standard light projector used by the Navy and Marine Corps is the ML-121 ceiling light projector, shown in figure 2-43. This equipment projects a narrow, concentrated beam of light vertically onto cloud bases up to 10,000 feet. An observer, sighting at the illuminated spot on a cloud base, uses clinometer elevation angle and baseline distance to find cloud height. The light projector is effective only at night. Operation The ceiling light projector is activated by a switch located in the weather office or outside near the observation point. The projector must be activated only when conducting a measurement. The high-intensity light may confuse pilots, both ashore and aboard ship; therefore, you must request permission from your supervisor to activate the projector. Figure 2-43.—ML-121 ceiling light projector. Maintenance Ground electronics personnel should provide maintenance support for the projector. Maintenance procedures are described in NA 50-30FR-521, Handbook, Operation and Maintenance Instructions, Ceiling Light Projector ML-121 and Clinometer ML- 119. Recommended operator maintenance includes the following: Weekly cleaning of glass cover plate and inspection and cleaning of drainage/ventilation holes in the projector housing Replacing lamps that are burned out or have blackened or sagging filaments Quarterly checking of lamp alignment and focus, and inspecting the projector to make sure it is level CLINOMETER Clinometers are used to measure the elevation angle of the projected light spot on a cloud base. Two different types of clinometers are used: the ML-119 clinometer, found only at shore stations, and the ML-591/U 2-33