X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 16 May 2005 22:32:54 -0400 Message-ID: X-Original-Return-Path: Received: from pebblebeach.tangiblesoftware.com ([65.222.219.103] verified) by logan.com (CommuniGate Pro SMTP 4.3c5) with ESMTP id 946779 for lml@lancaironline.net; Mon, 16 May 2005 22:13:59 -0400 Received-SPF: none receiver=logan.com; client-ip=65.222.219.103; envelope-from=tspear@tangiblesoftware.com Received: from Lexington (unknown [192.168.0.1]) by pebblebeach.tangiblesoftware.com (Postfix) with ESMTP id 3B18C268006; Mon, 16 May 2005 22:13:08 -0400 (EDT) From: "Timothy Spear" X-Original-To: "'Lancair Mailing List'" X-Original-Cc: "Timothy Spear" Subject: Airplane Construction Philosophy X-Original-Date: Mon, 16 May 2005 22:13:09 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_003C_01C55A64.71A8BB40" X-Mailer: Microsoft Office Outlook, Build 11.0.6353 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 Thread-Index: AcVahfhNCeJBilbtQvCS9Pwmo9YCUg== X-Original-Message-Id: <20050517021308.3B18C268006@pebblebeach.tangiblesoftware.com> This is a multi-part message in MIME format. ------=_NextPart_000_003C_01C55A64.71A8BB40 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Hello all, Working in the computer field I was wondering why so much time in the aircraft industry is concerned with minimizing the mean time between failure (MTBF) on a single component. For example in the computer field we have moved extensively to a concept called RAID (Redundant Array of Inexpensive Disks), in the "old" days a mainframe disk drive with an average of a one MTBF every million hours cost tens of thousands, versus a PC drive had an MTBF of a thousand hours and sold for a few hundred. With RAID you would mirror the data between two PC drives, and the chance then of a both failing at the same time was back up to a million hours. Two PC drives would cost significantly less than the equivalent mainframe, the result is that the cost of disk drives for servers has gone down significantly. In addition, computer staff has become used to a failure mode for disk drives resulting in reduced data loss and better recovery procedures. In the aircraft industry we have continued to engineer for the MTBF of a million hours, with two consequences. One, everything is very expensive, two pilots are not used to any failures; so when a failure occurs the pilot does not know how to effectively deal with it. Therefore, why do we not accept a lower MTBF and have two complete avionics systems, fly by wire controls, engines.. The point could continue to everything except core structural elements. Tim ------=_NextPart_000_003C_01C55A64.71A8BB40 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

Hello all,

         =    Working in the computer field I was wondering  why so much time in the = aircraft industry is concerned with minimizing the mean time between failure = (MTBF) on a single component. For example in the computer field we have moved = extensively to a concept called RAID (Redundant Array of Inexpensive Disks), in the = “old” days a mainframe disk drive with an average of a one MTBF every million = hours cost tens of thousands, versus a PC drive had an MTBF of a thousand = hours and sold for a few hundred. With RAID you would mirror the data between two = PC drives, and the chance then of a both failing at the same time was back up to a = million hours. Two PC drives would cost significantly less than the equivalent = mainframe, the result is that the cost of disk drives for servers has gone down = significantly. In addition, computer staff has become used to a failure mode for disk = drives  resulting in reduced data loss and better recovery procedures. In the = aircraft industry we have continued to engineer for the MTBF of a million hours, = with two consequences. One, everything is very expensive, two pilots are not = used to any failures; so when a failure occurs the pilot does not know how to effectively deal with it. Therefore, why do we not accept a lower MTBF = and have two complete avionics systems, fly by wire controls, engines…. The = point could continue to everything except core structural = elements.

 

 

Tim

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