OA-7900A/GMQ-10 CONVERTER/INDICATOR GROUP

Required AN/GMQ-32 Recorder Chart Notations Transmissometer recorder charts (fig. 2-36) should be set to Coordinated Universal Time (UTC); they must have a time check with a date-time group entered at the following times: The beginning and end of each roll The actual time of each synoptic hour observation The beginning and ending of maintenance shutdowns or other periods when the recorder is not in service When you are notified of any aircraft mishap at or near your station Figure 2-36.—AN/GMQ-32 transmissometer recorder chart notations. In addition to the regular time checks with a date- time group, other notations are required on the recorder chart on the following occasions: When the chart time differs by more than 5 minutes from the actual time. (Place a date-time group on the position the pen was recording on the chart, correct the chart time position, and enter a new date- time group on the adjusted position.) When a chart or any portion of the chart is provided for any special study or investigation. (Enter the station name, runway number, length of the baseline, and month and year on the chart, in addition to the required time checks.) OA-7900A/GMQ-10 CONVERTER/INDICATOR GROUP The OA-7900A/GMQ-10 converter/indicator group, consisting of an ID-1939/GMQ-10 digital LED visibility indicator and a CV-3125/GMQ-10 signal converter (fig. 2-37), was added to most AN/GMQ-10 systems in the early 1970’s. The original ID-l939 visibility indicators used an electromechanical display dial that was very difficult to maintain and suffered a great deal of downtime. The display dials were removed in the mid-1970’s and replaced with programmable-read-only-memory (PROM) computer chips and an LED readout for runway visual range (RVR), in hundreds of feet. Operation The OA7900/GMQ-10 will provide readouts for two different visibility readings. It provides sector visibility, in the vicinity of the runway, and runway visual range. Operating the OA7900/GMQ-10 in NORMAL mode yields sector visibility. Operating the converter in DAY or NIGHT mode, and setting the Light-setting switch to the indicated runway-lighting intensity, activates different calculations in the memory to yield runway visual range. No correction for background illumination is required. Check with the air traffic controllers to verify the runway light-intensity setting. Runway lights are frequently operated at setting 2 or 3, but a pilot may request that the level (setting) be changed. Level 1 is dimmest and 5 brightest. Ideally, the setting used is the lowest setting that lights can be seen through any obstruction to visibility. Study the operator’s manual NA 50- 30GMQ10-7, Operator and Maintenance Instructions with Illustrated Parts Breakdown, OA-7900A/GMQ- 10, for further details on operating and maintaining this system. 2-28