X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 1 [X] Return-Path: Sender: To: lml Date: Tue, 19 Dec 2006 09:05:56 -0500 Message-ID: X-Original-Return-Path: Received: from imo-m28.mx.aol.com ([64.12.137.9] verified) by logan.com (CommuniGate Pro SMTP 5.1.3) with ESMTP id 1690787 for lml@lancaironline.net; Tue, 19 Dec 2006 08:47:11 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.12.137.9; envelope-from=MikeEasley@aol.com Received: from MikeEasley@aol.com by imo-m28.mx.aol.com (mail_out_v38_r7.6.) id q.bd0.ae34273 (32915) for ; Tue, 19 Dec 2006 08:46:18 -0500 (EST) From: MikeEasley@aol.com X-Original-Message-ID: X-Original-Date: Tue, 19 Dec 2006 08:46:15 EST Subject: Re: [LML] Re: electric attitude indicators X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1166535975" X-Mailer: 9.0 Security Edition for Windows sub 5354 X-Spam-Flag: NO -------------------------------1166535975 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Jeff and Doug, I don't remember hearing failure rates expressed in percentages but typically MTBF. One percent (1%) could mean that only 1% of Cheltons ever fail, or that they work 99% of the time, or something else. If you think about it, 99% is pretty lousy. That could mean the Chelton's out of service a couple minutes every flight. The more features we cram into one box, the failure rate has to climb. Not like the good ol' days when only one instrument or one radio would quit. So we may disagree on how often something will fail and even whether a certain failure rate is acceptable. I think the important this is they DO fail, whether it's once a decade or once a month. Either way, we need to have some backup for WHEN they fail. Murphy's Law would suggest that whenever the failure happens, it will be at the worst possible time. Mike -------------------------------1166535975 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
Jeff and Doug,
 
I don't remember hearing failure rates expressed in percentages but=20 typically MTBF.  One percent (1%) could mean that only 1% of Cheltons e= ver=20 fail, or that they work 99% of the time, or something else.  If you thi= nk=20 about it, 99% is pretty lousy.  That could mean the Chelton's out of=20 service a couple minutes every flight.  The more features we cram into=20= one=20 box, the failure rate has to climb.  Not like the good ol' days when on= ly=20 one instrument or one radio would quit.
 
So we may disagree on how often something will fail and even whether a=20 certain failure rate is acceptable.  I think the important this is they= DO=20 fail, whether it's once a decade or once a month.  Either way, we need=20= to=20 have some backup for WHEN they fail.  Murphy's Law would suggest that=20 whenever the failure happens, it will be at the worst possible time.
 
Mike
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