AEROGRAPHER'S MATE 3 & 2 



CEILING LIGHT PROJECTOR ML-121 



The Ceiling Light Projector ML-121 (fig. 

 5-4) consists of a drum and an optical system. 

 The drum is a weatherproof one-piece casting 

 which holds the various parts of the projector 

 in their correct positions. Leveling perches, 

 90° apart, are adjusted so that the beam is 

 directed at the zenith when both perches are 

 level. 



The optical system consists of the lamp, 

 primary reflector, secondary reflector, socket 

 assembly, supporting base, and transformer. 



The primary reflector is a parabolic mirror 

 constructed of silvered, high-transmission 

 glass, while the secondary reflector is 

 a spherical, silvered glass mirror, both of 

 which do not crack when subjected to repeated 

 heating and cooling cycles. 



The secondary reflector is held in a spherical 

 reflector holder which is rigidly mounted on 

 an arm of the socket assembly so that the 

 focal points of the reflector and lamp coincide. 



SOCKET 

 ASSEMBLY 



DOOR 

 CLAM 



SECONDARY 

 REFLECTOR 



DOOR 

 CLAMP 



COVER 

 GLASS 

 DOOR 



LAMP 



PRIMARY 

 REFLECTOR 



DRUM 



TRANSFORMER 



TRANSFORMER 

 HOUSING 



CONVENIENCE 

 OUTLET 



LEVELING 

 PERCH 



SLIP 

 FITTER 



209.110 

 Figure 5-4. — Ceiling light projector ML-121 

 detail. 



The socket assembly consists of a cast 

 aluminum or iron base and is located so that 

 it supports the lamp at the focal point of the 

 secondary reflector. 



The base of the projector is a single casting 

 for both the transformer housing and slip 

 fitter. The slip fitter is designed to fit over 

 a 4- inch standard pipe with sufficient play to 

 permit leveling of the drum by four setscrews. 



Operation 



The ceiling light projector should be in- 

 stalled so that a standard baseline (horizontal 

 distance from projector to observation point) 

 near 800 feet can be established and so that 

 supplementary baselines near 400 and 1,600 

 feet can be marked when practicable. 

 The 400-foot baseline is for use when clouds 

 are below 500 feet; the 1,600-foot baseline 

 is for use when clouds are above 10,000 feet. 



It is not necessary for the observation 

 point and the projector to be at the same level 

 when the clinometer is used. The control switch 

 should be convenient to the observation point, 

 so that the light need not be turned on for a 

 period of time longer than required to obtain 

 an observation. Since the ceiling light projector 

 is generally close to the field, never leave 

 it on any longer than necessary, as the power- 

 ful light may blind night-flying pilots during 

 a field approach. When at all practicable, the 

 line of sight should be from south to north 

 in order to avoid the occasional inconvenience 

 due to moonlight on thin cloud patches. The 

 projector must be carefully leveled, and the 

 level must be checked frequently to ensure a 

 true vertical light beam. The lamp should 

 be focused so as to throw a narrow, concen- 

 trated shaft of light. 



Maintenance 



In order to ensure full beam intensity, 

 clean the cover glass on the projector housing 

 and the reflector's surfaces once a week or 

 oftener as necessary. Liquid glass cleaners or 

 other nonabrasive glass cleaners, used with 

 soft clean cloths, are recommended for this 

 maintenance. 



Inspect the drainage holes in the mirror and 

 housing, and clean them as often as is necessary 

 to ensure adequate drainage and ventilation 

 of the enclosure. 



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