Return-Path: Sender: (Marvin Kaye) To: lml Date: Mon, 22 Sep 2003 21:06:18 -0400 Message-ID: X-Original-Return-Path: X-SpamCatcher-Score: 1 [X] Received: from siaag1ae.compuserve.com ([149.174.40.7] verified) by logan.com (CommuniGate Pro SMTP 4.1.3) with ESMTP id 2589708 for marv@lancair.net; Mon, 22 Sep 2003 18:10:04 -0400 Received: (from mailgate@localhost) by siaag1ae.compuserve.com (8.12.9/8.12.7/SUN-2.7) id h8MMA2Xf001880 for marv@lancair.net; Mon, 22 Sep 2003 18:10:02 -0400 (EDT) X-Original-Date: Mon, 22 Sep 2003 18:05:43 -0400 From: James Frantz Subject: Please post this AOA message for me X-Original-Sender: James Frantz X-Original-To: Marve Kaye X-Original-Message-ID: <200309221805_MC3-1-4F77-FC86@compuserve.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=ISO-8859-1 Content-Disposition: inline After talking with Ron about his accident I asked him to post a message about how the AOA gets information as I didn't have access to the mail li= st at that time. I thought a review should be addressed to the mail list regarding AOA and when it can be used as a backup to faulty IAS and pitot/static systems. The PSS AOA system uses both wing loading and pitot static pressures to gauge AOA. The wing loading is determined by measuring the differential pressure between the lower and upper wing static. A pitot/static pressur= e is used by the AOA to get dynamic pressure and is usually gotten from the= existing system although some folks install a separate pitot/static syste= m dedicated to the AOA. AOA is derived by dividing the wing loading by the dynamic pressure. Should the IAS indicator fail, certainly the AOA would make an excellent source. However, if the pitot/static system fails (covered pitot tube fo= r example) then the dynamic pressure is in error and the IAS indicator and the AOA will both give invalid indications; garbage in garbage out. Ron reported that the pitot tube was covered by tape or clogged by mud-daubers This results in the dynamic system pressures being falsely low in relation to the speed. This system error would have resulted in a= low airspeed indication and a high AOA indication. = I hope this helps. Jim Proprietary Software Systems, Inc. www.angle-of-attack.com (952) 474-4154 Jim Proprietary Software Systems, Inc. www.angle-of-attack.com (952) 474-4154