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[1] The Federal Aviation Administration (FAA) required installation of GPWS (Ground Proximity Warning System) in all commercial airplane. The purpose is to alert the flight crew to the existence of an unsafe condition due to terrain proximity. The various hazardous conditions that can be encountered in flight are divided into five modes. These are:
Mode 1 --------- Excessive descent rate
Mode 2 --------- Excessive closure rate with respect to rising terrain
Mode 3 ------- Excessive altitude loss during climb-out (in takeoff or during go-around)
Mode 4 ------- Insufficient terrain clearance when not in landing configuration (Landing gear up and/or flaps less than 25 unit )
Mode 5 ------- Excessive deviation below glide slope when making a front course approach with the gear down.
Fig. 33-1 Ground proximity warning
[2] The main component of the ground proximity warning system is the ground proximity warning computer (GPWC). It establishes the limits for the warning modes and compares the airplane flight and terrain clearance status against the established mode limits. If the airplane is found to have entered the envelope for one of the warning modes, the computer issues appropriate warning or alerting signals. The computer stores failure data in a non-valatile memory for display in a front panel window. Various parameters are received from interfacing systems and used to compute the airplane's status with respect to ground proximity warning system modes. These input parameters consists of discretes, analog signals and digital data words. The output signals for the activation of visual indicators consist of discretes transmitted to illuminate the red PULL UP lights, the amber BELOW G/S lights, and the red WINDSHEAR messages. Aural outputs are sent to the captain's and first officer's flight compartment speakers and headphones. 中國航空網 www.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：第31課 大氣數據系統 LESSON 31 AIR DATA SYSTEM(11)
