Return-Path: Received: from [69.171.36.121] (account marv@lancaironline.net) by logan.com (CommuniGate Pro WebUser 4.2.2) with HTTP id 421467 for lml@lancaironline.net; Sun, 19 Sep 2004 13:31:37 -0400 From: "Marvin Kaye" Subject: Re: [LML] Re: AOA To: lml X-Mailer: CommuniGate Pro WebUser Interface v.4.2.2 Date: Sun, 19 Sep 2004 13:31:37 -0400 Message-ID: In-Reply-To: <002501c49e58$d25eb7f0$6401a8c0@axs> References: <002501c49e58$d25eb7f0$6401a8c0@axs> X-Priority: 3 MIME-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format="flowed" Content-Transfer-Encoding: 8bit Posted for "terrence o'neill" : Skip. Thanks for adding your pewrsonal experience to truth. The Navy learned the value of AOAs when in 1956, shocked at the crash rate when they began landing jets on carriers at 140-mph in stead of Bearcats at 90 mph, they changed all carriers to AOAs, at GREAT expense. It was proved worth it, in curtting the crash rate FIFTY PERCENT the first year; and they have refined it and kept the system ever since. Mark obviously lacks understanding of how relative wind uses an airfoil to develop lift; and, how the pilot really controls his airplanes lift -- by using his pitch control to control the ANGLE at which the wing enters the relative wind. I did a solid month of research on AOA in 1998 to write an 8-page article for KITPLANES, starting on page 96, with encouragement of its then editor Dave Martin, who knew very well the value of AOA, having been a back-seater in F4s with many carrier landings. Because pilots are trained by doing, like riding a bicycle, -- instead of by understanding in order to design an airplane to make it fly -- they are reasonably very cautious about changing how they have come to think about flying. EVEN IF IT IS WRONG. Because they don't know. In fact many of them resent it, like Mark. I can testify to that after trying to explain the AOA for 40 years! Even the head of the FAA's Safety Office I talked to, back when Najeeb Hallaby was head of the FAA, didn't understand the AOA, and that it was THE most BASIC instrument possible, even moreso, or equal to, the horizon. That is: a wing airfoil can produce lift and ANY speed, even one mph; and, the wing airfoil produces more lift at greater angles; and, at some increased angle peculiar to that airfoil, the airflow will start to break away and the lift will drop to about half, the stall, usually occurring at between 8 to 25 degrees, depending on the sharpness of the leading edge, the airfoil thickness, the camber, and the planform/aspect ratio/sweepback. Since sirflow is invisible, the conservative FAA still teaches tyro pilots 'stall speed', which is a secondary indicator. That term really means the indicated speed of stall at one G and/or weight, and can, in a C206 for instance, vary so much as to be almost useless... depending on t/o weight. An AOA, on the other hand, enables a pilot to SEE, with his EYEBALLS, how close he is flying his wing to its STALL AOA. He instantly controls this angle with his pitch control, almost as if the indicator were attached to the elevator. With an AOA like the ones I made a pilot can SEE THE ANGLE accurate to a degree, and fly the plane throuogh all kinds of maneuvers, unusual attitudes, steep turns on Final, and so on, and avoid stalling by avoiding pulling back too far on the pitch control. But if he tried this without and AOA ...it is walking along a cliff with a blindfold on. He can't SEE what he's doing. It is incredibly difficult to communicate these simple ideas to pilots. They know how to work the machine pretty well, but they don't UNDERSTAND what's happening with the air and the wing. Perhaps these and Skip's comments will help fix that. Any other comments are invited. T.