X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sat, 12 Jan 2008 14:28:53 -0500 Message-ID: X-Original-Return-Path: Received: from imo-d23.mx.aol.com ([205.188.139.137] verified) by logan.com (CommuniGate Pro SMTP 5.2c4) with ESMTP id 2640900 for lml@lancaironline.net; Fri, 11 Jan 2008 10:37:08 -0500 Received-SPF: pass receiver=logan.com; client-ip=205.188.139.137; envelope-from=Sky2high@aol.com Received: from Sky2high@aol.com by imo-d23.mx.aol.com (mail_out_v38_r9.3.) id q.be5.223de061 (14501) for ; Fri, 11 Jan 2008 10:36:25 -0500 (EST) From: Sky2high@aol.com X-Original-Message-ID: X-Original-Date: Fri, 11 Jan 2008 10:36:25 EST Subject: Re: [LML] Single Point Failures X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1200065785" X-Mailer: Unknown sub 34 X-Spam-Flag: NO -------------------------------1200065785 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Rob, "There is no fool proof device. Fools are so ingenious." Anom Yep, I certainly agree with those bottom lines. After all, almost all of us still operate with only one (1) pitot tube. What good is my AOA device and two airspeed indicators if they use the same reference source? Scott In a message dated 1/11/2008 8:52:10 A.M. Central Standard Time, rwolf99@aol.com writes: While designing the Javelin Jet we wrestled with single-point failures all the time. The electrical guys were constantly telling us "but the systems are electrically separated, the functions are on different cards, each board has its own power supply, there are metal dividers between the boards -- why do you care that it's all in the same box?" We responded "everything goes in one cable to that box and what if that gets cut, a fire caused by something else could take out the entire box" and so forth. Your example of water dripping on the box or the spilled coffee in the movie "Fate is the Hunter" are examples of external factors causing multiple failures in distributed systems that happen to all reside at the same physical spot. In my little Lancair, however, I don't think physical separation of my electrical systems will protect me from a fire on one side of the cockpit. It may help me, though, if the canopy starts leaking or if a passenger barfs on the circuit breaker panel... The bottom lines are: 1) Do what you can, but realize there is a point of dimishing returns, but ... 2) Murphy is out there ... **************Start the year off right. Easy ways to stay in shape. http://body.aol.com/fitness/winter-exercise?NCID=aolcmp00300000002489 -------------------------------1200065785 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
Rob,
 
"There is no fool proof device.  Fools are so ingenious."=20 Anom
 
Yep, I certainly agree with those bottom lines.  After all, almost= all=20 of us still operate with only one (1) pitot tube. What good is my AOA device= and=20 two airspeed indicators if they use the same reference source? 
 
Scott
 
In a message dated 1/11/2008 8:52:10 A.M. Central Standard Time,=20 rwolf99@aol.com writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>While=20 designing the Javelin Jet we wrestled with single-point failures all the=20 time.  The electrical guys were constantly telling us "but the system= s=20 are electrically separated, the functions are on different cards, each boa= rd=20 has its own power supply, there are metal dividers between the boards -- w= hy=20 do you care that it's all in the same box?"

We responded "everythin= g=20 goes in one cable to that box and what if that gets cut, a fire caused by=20 something else could take out the entire box" and so forth.  You= r=20 example of water dripping on the box or the spilled coffee in the mov= ie=20 "Fate is the Hunter" are examples of external factors causing multipl= e=20 failures in distributed systems that happen to all reside at the same phys= ical=20 spot.

In my little Lancair, however, I don't think physical=20 separation of my electrical systems will protect me from a fire on one sid= e of=20 the cockpit.  It may help me, though, if the canopy starts leaking or= if=20 a passenger barfs on the circuit breaker panel...

The bottom lines=20 are:

1)  Do what you can, but realize there is a point of=20 dimishing returns, but ...
2)  Murphy is out there=20 ...



Easy ways to st= ay in shape in the new year.
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