X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: <marv@lancaironline.net> Sender: <marv@lancaironline.net> To: lml@lancaironline.net Date: Thu, 23 Jun 2005 00:43:49 -0400 Message-ID: <redirect-1010916@logan.com> X-Original-Return-Path: <Christopher.Zavatson@udlp.com> Received: from mta-out-1.udlp.com ([207.109.1.8] verified) by logan.com (CommuniGate Pro SMTP 4.3.4) with ESMTP id 1010883 for lml@lancaironline.net; Wed, 22 Jun 2005 23:58:56 -0400 Received-SPF: pass receiver=logan.com; client-ip=207.109.1.8; envelope-from=Christopher.Zavatson@udlp.com Received: from asdmngwia.udlp.com (asdmngwia.mpls.udlp.com [10.1.62.22]) by mta-out-1.udlp.com (8.12.10/8.12.10) with ESMTP id j5N1dOu2012097 for <lml@lancaironline.net>; Wed, 22 Jun 2005 20:39:24 -0500 Received: from DM-MN-06-MTA by asdmngwia.udlp.com with Novell_GroupWise; Wed, 22 Jun 2005 22:58:09 -0500 X-Original-Message-Id: <s2b9ed01.056@asdmngwia.udlp.com> X-Mailer: Novell GroupWise Internet Agent 6.5.4 X-Original-Date: Wed, 22 Jun 2005 22:58:33 -0500 From: "Christopher Zavatson" <Christopher.Zavatson@udlp.com> X-Original-To: <lml@lancaironline.net> Subject: [LML] Re: Induction air filter Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Walter, <<We have watched many detonation events--some=20 even heavy detonation events--some for extended periods-without any=20 ill effects on the piston, cylinder or engine in general. The danger=20 is these turning into pre-ignition, usually from a damaged spark plug=20 from the detonation. That can destroy the engine in 30 seconds and=20 while our observations are that detonation doesn't hole a piston,=20 pre-ignition will do it in a heartbeat.>> Now I'm confused. =20 A few year back my plane was topped off with 20 gallons of fuel that was = about 95% avgas and 5% Jet A. I didn't notice anything unusual while = operating the engine. 6 flight hours later, I and 200 other unlucky = aircraft owners were informed of the fuel contamination. Upon removal of = the cylinders and connecting rods, we found that the rear pistons had been = almost completely cleaned of all carbon deposits and a new uniform deposit = layer had started forming. The front pistons had not been so completely = cleaned and so the much of the original carbon deposit layer was still = present. It had a coarsely pitted appearance. The exhaust valve seats = had turned blue. Also, the babbitt in the connecting rods bearings had = been smeared against the crank. =20 The diagnosis at the time was detonation. Do you agree? The scary part = is that I couldn't tell anything was amiss. All indications in terms of = sound, feel and temperatures were within typical operating ranges, yet it = caused the engine to be scrapped. I imagine the plugs were not damaged as = they continued to fly for six hours without any sign of trouble. I = probably had 3 hours on a 2.5% blend of Jet A and 3 more on something much = more dilute. The engine was a completely stock Lyc. 0-360A1A with 300 = hours since new. I was left with the impression that a little (not = noticeable) detonation over a long period of time (a few hours) will = destroy an engine. =20 In the affected group, turbo charged engines, modified engines (hi-comp = pistons etc.) and those receiving the highest concentrations of Jet-A did = almost come apart at the seams leading to a number of emergency landings. Chris Zavatson N91CZ + engine #2 360 std