X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 10 [X] Return-Path: Sender: To: lml@lancaironline.net Date: Sun, 29 Apr 2007 17:55:37 -0400 Message-ID: X-Original-Return-Path: Received: from jrcda.com ([69.36.178.59] verified) by logan.com (CommuniGate Pro SMTP 5.1.8) with ESMTP id 2016370 for lml@lancaironline.net; Sun, 29 Apr 2007 13:41:51 -0400 Received-SPF: none receiver=logan.com; client-ip=69.36.178.59; envelope-from=hwasti@starband.net Received: from [192.168.1.101] (cbl-238-61.conceptcable.com [207.170.238.61] (may be forged)) (authenticated bits=0) by jrcda.com (8.12.11.20060308/8.12.11) with ESMTP id l3THeqXc017653 for ; Sun, 29 Apr 2007 11:40:53 -0600 X-Original-Message-ID: <4634D8A2.3030105@starband.net> X-Original-Date: Sun, 29 Apr 2007 10:40:50 -0700 From: "Hamid A. Wasti" User-Agent: Thunderbird 1.5.0.10 (Windows/20070221) MIME-Version: 1.0 X-Original-To: Lancair Mailing List Subject: Re: [LML] Re: 12v supply to stabilize avionics References: In-Reply-To: Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Mike,

I have not read the particular article you cited (no time) but I am familiar with Bob's position on the this subject.  He correctly asserts that most properly designed modern avionics should not get harmed by being on during engine start.  The supposed "spikes" during engine start that are so fatal to avionics are just myths. 

That said, there is another issue that needs to be considered.  If you have additional loads active while you are cranking the engine, you putting additional strain on the battery.  Is the additional strain from having a simple engine monitor significant?  Most probably not.  Is the additional strain from turning on the entire avionics stack, pitot heat, position lights, strobe and landing light significant?  Absolutely.  The threshold of what is acceptable lies somewhere between the two extremes and I can not tell you where that is.  It is a decision that you need to make, both as the designer and as the pilot.

The second issue is whether the avionics are "properly designed."  The avionics that we can install in experimental birds do not have to meet DO-160 and many (most?) will not survive the over-voltage and possibly the under-voltage tests.  DO-160 requirements, compiled by the private firm RTCA and not the FAA, are not there because some FAA bureaucrat had a fight with his mistress and decided to take it out on the aviation community by coming up with some unreasonable requirements.  These requirements are there because it has been shown, either analytically or anecdotally, that those conditions can and do exist in real life.  It is up to you, as a manufacturer, what level of testing, if any, you want done on the electronics that go in your airplane.

Regards,

Hamid


MikeEasley@aol.com wrote:
Most of us need to have some avionics turned on for engine starting so we have our engine monitor up a running for initial oil pressure readings, etc.  Bob Nuckols at the Aeroelectric Connection has some very strong opinions on avionics during engine start.
 
 
Mike Easley