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
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