From: firstname.lastname@example.org (Terrell D. Drinkard) Organization: Boeing Commercial Airplane Group Date: 21 Apr 94 23:18:38 References: 1
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In article <email@example.com>, Tobias Henry Lutterodt <luterodt@phoenix.Princeton.EDU> wrote: > >There have been a number of incidents lately (Singapore 747-400 and others) >where a jetliner has stalled at high speed at or near cruising altitude. > >I don't understand how this happens...could someone explain? In general, a high speed stall in a commercial jet transports occurs because the wing is put at too high an angle of attack (this is actually the general definition of a stall). The wing at cruise is working quite hard, with the midspan and outboard wings near their maximum coefficients of lift. A small change in angle of attack can cause flow separation and subsequent loss of lift. This change in angle of attack can be caused by pitching the airplane up with the elevators, or by deploying high-lift devices (a la the MD-11 that had to land at Shemya). The airplane can also stall because it is moving so fast that the shockwave along the upper surface of the wing becomes so strong that the flow separates behind it. This is a Mach buffet. Contributing factors are weight (which falls out as an angle of attack) and ambient air conditions. -- Terry firstname.lastname@example.org "Anyone who thinks they can hold the company responsible for what I say has more lawyers than sense."