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Terrain Warning

Old 15th Jun 2007, 15:35
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Terrain Warning


question: what happens if i fly with gear down and flaps 25 towards rising terrain. When does the system cry pull up terrain terrain and when not. Talking about the 737 classic AND the NG

thanks so much!

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Old 15th Jun 2007, 20:47
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Olendirk Information on the operation of the Enhanced GPWS (EGPWS) is available from www.egpws.com See Operation - pilots guides; I think that you need the Mk V and Mk VII.

The Enhanced system will provide ‘amber’ Terrain Ahead alerts with approximate 60 sec lead time, and a ‘red’ Terrain Pull Up warning at approx 30 sec before the aircraft encounters terrain / or obstacle. The times vary with the terrain and several flight parameters.

Other information is provided in the web page General Information section, which includes examples and videos.

Your question suggests possible confusion with the basic version of GPWS where flap and gear selection did restrict the type of warning given. The basic GPWS features are still in the Enhanced system, but rarely encountered as the look-ahead feature provides superior alerting. However, if the enhanced features fail or are selected off, then in most aircraft installations the basic GPWS remains active (depends on sensor inputs). For an example of this see incident #8 from the ICAO library Celebrating TAWS ‘Saves’: But lessons still to be learnt.

Also see the latest issue (02/2007) of the ICAO Journal and the article - Recent Issues with TAWS, which provides a good overview of current operational problems.
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