X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [69.171.58.236] (account marv@lancaironline.net) by logan.com (CommuniGate Pro WebUser 5.0.9) with HTTP id 1125721 for lml@lancaironline.net; Wed, 24 May 2006 00:17:55 -0400 From: "Marvin Kaye" Subject: Re: How Not to Do 1st Runup To: lml X-Mailer: CommuniGate Pro WebUser v5.0.9 Date: Wed, 24 May 2006 00:17:55 -0400 Message-ID: In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format="flowed" Content-Transfer-Encoding: 8bit Posted for Gary Casey : Normally, with a main gear (like on a Cessna) the assumption is that the only load on the main downlocks is the weight of the gear itself. When on the ground the weight of the aircraft holds the gear in the "down" position. In order to retract the gear initially goes down - straight down on a Cessna, but I don't know the details of the geometry on the LIV - but alternatively, the aircraft could be lifted to allow the gear to retract. Remove much of the weight on the mains, and then probably double the thrust and the loading on the downlocks is probably more than they are designed to withstand, the plane lifts as the gear folds. Artificially restraining the wheels with chocks shouldn't be a problem as the limit is the coefficient of friction to the ground, probably higher with a locked wheel than between the block and the ground, although one block flying out might have put an impact load on the other gear, which could have started the chain reaction. I'd put my bet on the lack of thought in planning the test as being the root cause. If one is going to restrain a plane in a test like that, doing it closer to the center of thrust would reduce the abnormal loading on all components. I'd vote for restraint cables attached at the root of the gear legs. Gary Casey