From: "G. E. Lambert" <firstname.lastname@example.org> Organization: Netcom Date: 21 Dec 95 03:33:11 References: 1 2
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When in landing configuration (they were) the GPWS must sense "excessive" rate of closure with terrain, as measured by a radio altimeter that is looking straight down, not forward. "Excessive rate" is a function of radio altitude. Obviously, the system must permit rates on the order of 700 to 1000 fpm or no landing could ever be completed without a warning. In this incident, the rates apparently never exceeded the "excessive" threshold. If they had I think the outcome would have been much different (much worse).