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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400
MAINTENANCE MANUAL
Range processing is accomplished by the range module, which is a two-processor subsystem containing the hazard processor and range converter. The range converter performs range scan conversion and sends ARINC 453 output data to the video processor.When the airplane is on the runway or in the air, the qualifier-A and qualifier-B discrete inputs become valid. These are used by a fully operational RDR-4B windshear system to automatically turn on the radar system. The antenna stabilization processor switches on the antenna drive module, which then sends power to the antenna drive motors. These qualifiers have no effect on airplanes that have only windshear provisions.Standby Mode 1) The RDR-4B radar system is placed in the standby mode
whenever the airplanes 115V AC power is applied to the left and right R/Ts. The EFIS control panel WXR switch will be in the off position. The following conditions apply to the WXR radar in the standby mode. a) No power is applied to the antenna by the RDR-4B R/T. b) The R/T transmitter is inhibited. c) The ARINC 453 data output from the R/T to the
navigation displays is inhibited.
d) The frequency module is deactivated.
e) The following R/T circuits are operational.
1.
Master processor module to perform automatic
_ activation of the windshear mode, if required.
2.
Maintenance processor module, to maintain active
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interface to the CMS.Weather Mode 1) During the weather mode, the master processor generates
timing to produce 6-microsecond and 18 microsecond transmitter pulses. The time module uses the input from the master processor to determine the pulse width. The data is received every 5.25 millisesconds. The processed output data is clocked out at 1-Mz rate to the signal module.
2) The sampled data is latched and applied as an input to the IQ processor which produces a sampled signal outut. For every 4 samples the IQ processor produces one IQ pair. This output is latched and applied to the filter processor. The filter processor provides low-pass filtering for the 6 and 18-microsecond pulse. During the output interval time, the processed radar signal is output from the time module to the frequency module.
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34-43-00
ALL ú ú 09 Page 28 ú Feb 18/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400 MAINTENANCE MANUAL
3) The time-domain signal from the timing module passes through the frequency module to the signal module. The frequency module is used only for processing predictive windshear data. The signal processor DSPs process the weather data, such as STC compensation, and send it to the range module. The data word from the signal module has 3960 range bins of weather data for a distance of 320 miles.
(q) Weather/Turbulence Mode 1) During the weather/turbulence mode, the master processor generates timing to produce nine 6-microsecond and one 18 microsecond transmitter pulses. The time module uses the input from the master processor to determine the pulse width. The data is received every 10.5 millisesconds. The processed output data is clocked out a 1-Mz rate to the signal module.
2) The processing for the weather/turbulence mode is similar to the weather mode as explained above.
(r) Windshear Mode 1) Windshear detection is accomplished by measuring the doppler frequency shift produced by out-flowing surface winds to microburst weather cells and then creating a velocity map from the data. This process, static ground clutter and moving-surface returns must be removed from the weather returns. 2) During windshear operation the frequency module is used to perform range doppler filtering. In any mode except windshear the common bus is controlled by the time module. In the windshear mode the frequency module takes control of the data bus and intercepts input data from the time module and outputs data to the signal module.
3) The range doppler filtering function consists of analyzing samples of incoming radar returns for each range bin to determine doppler shifts within expected minimum and maximum values. The amount of doppler shift is proportional to the relative velocity of the illuminated target with respect to the airplane reference. The doppler shifts provide a means of detecting both moving targets and measuring their relative velocity. This process generates a doppler frequency complex spectrum and then a magnitude spectrum for each range bin. The frequency complex spectrum correlates with random motions of rain droplets caused by weather turbulence.
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