X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 10 [X] Return-Path: Sender: To: lml Date: Thu, 21 Dec 2006 12:02:10 -0500 Message-ID: X-Original-Return-Path: Received: from jrcda.com ([69.36.178.59] verified) by logan.com (CommuniGate Pro SMTP 5.1.3) with ESMTP id 1698392 for lml@lancaironline.net; Thu, 21 Dec 2006 11:12:06 -0500 Received-SPF: none receiver=logan.com; client-ip=69.36.178.59; envelope-from=hwasti@starband.net Received: from [127.0.0.1] (cbl-238-61.conceptcable.com [207.170.238.61] (may be forged)) (authenticated) by jrcda.com (8.11.6/8.11.6) with ESMTP id kBLGBGL12742 for ; Thu, 21 Dec 2006 09:11:16 -0700 X-Original-Message-ID: <458AB21F.1060704@starband.net> X-Original-Date: Thu, 21 Dec 2006 08:11:11 -0800 From: "Hamid A. Wasti" User-Agent: Thunderbird 1.5.0.9 (Windows/20061207) MIME-Version: 1.0 X-Original-To: Lancair Mailing List Subject: [LML] System level reliability References: In-Reply-To: Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Fred Moreno wrote:

It would be interesting to know the causes of total electrical system failures in experimental aircraft, but we shall probably never know. My guess: a combination of poor system architecture coupled with poor workmanship standards on things like connectors, couplings, joints, wire chaffing protection and such.

I think the importance of good workmanship and proper component selection has not been emphasized enough. Not all diodes are created equal nor are all relays, all switches, all wires....... Not everyone is willing to invest in high quality crimping tools required to make a high reliability connection or invest the time to practice enough to be good at it.

Here are a couple of extreme examples. Lets say one copies the Columbia system schematic EXACTLY, but uses 10V/1A diodes. The diodes will blow the instant the system is powered up. Another person copies the system exactly including all the component choices. Instead of using proper connectors, this person just sticks stripped wires into receptacles and shoves in some toothpicks to keep them from falling out (I said this was an extreme example and yes I have personally seen that done in an automobile). Is that system even remotely reliable? Bottom line, an excellent paper design is just a starting point. It does not buy you any reliability unless it is backed up with proper component selection and good workmanship.

Looking over your design, I see one issue: Will the bus 1 to bus 2 diode keep you from reliably getting the low voltage warning on bus 2?

Regards,

Hamid