installations, is the OA-7900/GMQ-10 converter/
indicator group. It provides a LED digital display of
runway visual range in hundreds of feet.
The AN/GMQ-32 system is an upgrade of the
AN/GMQ-10 system. This major change replaced the
vacuum-tube electronics of the AN/GMQ-10 with
solid-state circuitry. The external appearance of the
equipment was not changed. The equipment still retains
the original identification plates.
The ID-353B/GMQ-10(B) or the ID-820/GMQ-
10(C) transmissometer indicator/recorder unit (fig.
2-35) is found in the observers work area of Naval
Meteorology and Oceanography detachments and
Marine Corps weather offices. The only visible
difference between the two models is that the
calibration setting meter is found only on the ID-353B,
which was originally designed for use overseas where
the local electricity did not conform to the carefully
maintained 60-hertz AC found in the United States.
The transmissometer equipment is normally left on.
It is turned off only for maintenance. If the system has
been turned off, start-up calibration adjustments are
required after a 1-hour warm-up period.
Detailed operational procedures for the upgraded
AN/GMQ-32 system, including the ID-353/GMQ-10
and ID-820/GMQ-10 transmissometer indicator/
recorder, are found in Air Force Technical Order
(AFTO) 31M1-2 GMQ-32-1, Operation Manual,
Transmissometer AN/GMQ-32, provided with each
Instructions provided in
NAVWEPS 50-30GMQ-10-2, Technical Manual,
Operation and Maintenance Instructions with
Illustrated Parts Breakdown, for the mechanical
components, such as the spring chart drive, are still
valid and may be used if the AFTO is not available.
Instructions and criteria for use of transmissometer data
are contained in NAVMETOCCOMINST 3141.2.
The transmissometer indicator/recorder provides
two output readings: the recorder graph and the
transmissivity meter. Both outputs provide
transmissivity percentages. Two sensitivity settings are
used to process incoming data. The indicator/recorder
is normally operated in the LOW sensitivity setting, but
the HIGH sensitivity setting may be used during low-
visibility conditions, when transmissivity falls below
20%. The HIGH setting simply multiplies the
indicator/recorder output by 5, which allows the
operator to read the output more accurately. Both
readings must be corrected for background illumination
and converted by using the tables provided in
NAVMETOCCOMINST 3141.2 to yield runway
visual range or sector visibility.
The background illumination correction is found by
placing the Background switch in the TEST position,
obtaining a background illumination level, and then
subtracting the background illumination level from the
transmissivity reading to obtain a corrected
The runway visual range (RVR) table in
NAVMETOCCOMINST 3141.2 is in two sections:
one for use during the day and the other for use at night.
Columns are provided for runway light settings (LS) 5,
4, 3, and Other. The Other column is used when runway
lighting is either not in operation or at setting 1 or 2. The
runway light setting is obtained from the air traffic
controllers. Use the transmissivity value in the proper
light setting column to find RVR.
General maintenance for the AN/GMQ-32 system
is performed by base ground electronics personnel or
trained METEM (METeorological Equipment
Maintenance) Electronics Technicians. Refer to the
care-and-use publications for more detailed
information. The following routine maintenance is
usually performed by the observer:
Replacing the recorder paperReplace the
paper by using the reloading diagram exposed in the
recorder window. Charts in continuous operation run at
3 inches per hour and are normally changed every 2
Rewinding the recorder chart drive
springRewind when setting the recorder chart time or
once per week. A fully wound drive will operate for 8
Adjusting the recorder zero adjustmentAdjust
daily when the recorder is in use
Refilling/cleaning the inkwell and pensEmpty
and clean inkwells, indicator pens, and marker pens
once a month. In many recorders, the inkwells have
been removed and pen cartridges have replaced the ink