Date: 06 Oct 97 02:14:26 From: John Weiss <John.R.Weiss@Boeing.*NOSPAM*.com> Organization: Boeing Commercial Airplane Group References: 1 2 3 4 5 6 Followups: 1
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jf mezei wrote: > > When flying at 42k feet which seems about the ceiling for commercial > passenger aircraft (except for Concorde), how long (max) would it take > for an engine-less plane to drop back to sea level an become a boat ? > > In other words, how long would the backup electrical and hydraulic system > really be needed for in the worse case scenario with a lightly loaded > plane ? Are we talking 10 minutes, 30 minutes, an hour before the plane > gets to sea level ? In round numbers (which may or may not be representative of any particular aircraft), assume: Glide speed of 200 Kts Glide ratio of 10:1 That gives a vertical speed of 20 Kts. From an altitude of 42,000' (7 miles), there is about 20 minutes of glide time available.