X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imf24aec.mail.bellsouth.net ([205.152.59.72] verified) by logan.com (CommuniGate Pro SMTP 4.3c5) with ESMTP id 930645 for flyrotary@lancaironline.net; Mon, 02 May 2005 22:06:35 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.152.59.72; envelope-from=ceengland@bellsouth.net Received: from [209.215.61.7] by imf24aec.mail.bellsouth.net (InterMail vM.5.01.06.11 201-253-122-130-111-20040605) with ESMTP id <20050503020550.ZVHJ2434.imf24aec.mail.bellsouth.net@[209.215.61.7]> for ; Mon, 2 May 2005 22:05:50 -0400 Message-ID: <4276DC7C.7050808@bellsouth.net> Date: Mon, 02 May 2005 21:05:48 -0500 From: Charlie England User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040804 Netscape/7.2 (ax) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: To Fuse or not to Fuse References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Bill Dube wrote: > >> >> Here is Bob K's and his well reasoned argument FOR fuses >> >> http://www.aeroelectric.com/articles/Rev9/ch10-9.pdf >> >> >> > > The keystone of Bob's endorsement of fuses: > > > When the failure manifests itself by opening the breaker or > fuse likelihood of recovering the system by replacing a > fuse or pushing in a breaker is very, very small. > > Beneath it all, this is what all the fuse versus circuit > breaker discussions hinge on. It is an incorrect assumption, in my > experience. > > A very large percentage (but by no means all) of electrical > problems in vehicles are intermittent in nature. You can very often > reset the breaker and restore the critical system long enough to > safely land the aircraft. A fuse does not give you this option, at > least not in a timely manner. To be realistic, don't most of the multi-reset stories start in old/poorly maintained/poorly designed/etc aircraft? I really think that the cornerstone(s) of his endorsement is more along the lines of 1. you don't have to have a 50 year old design & 'aircraft (poor) quality' factory electrical system in a homebuilt and 2. you can design critical-to-flight systems to have automatic or flip-a-switch backups. The reality is (as he's stated many times) *nothing* is failure proof. His philosophy is that you design the system with redundancy to trump any single failure. Everyone's got to make their own choices but it helps to start with the right assumptions. Charlie (I'll make the decision when it's time to pull wire.)