X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 06 Jan 2009 21:22:57 -0500 Message-ID: X-Original-Return-Path: Received: from [64.12.143.100] (HELO imo-m12.mail.aol.com) by logan.com (CommuniGate Pro SMTP 5.2.11) with ESMTP id 3411593 for lml@lancaironline.net; Mon, 05 Jan 2009 12:50:53 -0500 Received: from VTAILJEFF@aol.com by imo-m12.mx.aol.com (mail_out_v39.1.) id q.d40.32aec836 (37530) for ; Mon, 5 Jan 2009 12:50:45 -0500 (EST) Received: from smtprly-ma01.mx.aol.com (smtprly-ma01.mx.aol.com [64.12.207.140]) by cia-mb01.mx.aol.com (v121_r5.5) with ESMTP id MAILCIAMB013-5c48496248695; Mon, 05 Jan 2009 12:50:46 -0500 Received: from WEBMAIL-MY01 (webmail-my01.sim.aol.com [64.12.108.12]) by smtprly-ma01.mx.aol.com (v121_r5.5) with ESMTP id MAILSMTPRLYMA016-5c48496248695; Mon, 05 Jan 2009 12:50:33 -0500 References: X-Original-To: lml@lancaironline.net Subject: Re: [LML] Re: L-IVP Cracked Windshield X-Original-Date: Mon, 05 Jan 2009 12:50:33 -0500 X-AOL-IP: 75.58.185.119 In-Reply-To: X-MB-Message-Source: WebUI MIME-Version: 1.0 From: vtailjeff@aol.com X-MB-Message-Type: User Content-Type: multipart/alternative; boundary="--------MB_8CB3D753E109608_340_BD4_WEBMAIL-MY01.sysops.aol.com" X-Mailer: AOL Webmail 40627-STANDARD Received: from 75.58.185.119 by WEBMAIL-MY01.sysops.aol.com (64.12.108.12) with HTTP (WebMailUI); Mon, 05 Jan 2009 12:50:33 -0500 X-Original-Message-Id: <8CB3D753E04AA55-340-5DF@WEBMAIL-MY01.sysops.aol.com> X-Spam-Flag:NO ----------MB_8CB3D753E109608_340_BD4_WEBMAIL-MY01.sysops.aol.com Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii" I concur that the method of repair is problematic. Flying with a cracked windshield especially in a pressurized airplane is not recommended. If the window were to fail (worst case) is it would be catastrophic for the pilot?and passengers. I know this is not what one would like to hear but the only solution I see here is to remove and replace the windshield. Best Regards, Jeff -----Original Message----- From: REHBINC To: lml@lancaironline.net Sent: Mon, 5 Jan 2009 11:32 am Subject: [LML] Re: L-IVP Cracked Windshield Bill, ? My guess is that a residual stress was introduced when you replaced the brace after the gear failure. This has been acting on the windshield ever since, and along with operational loads, has given you this new crack. ? Drilling the crack tip will reduce the stress concentration from infinity to some calculable value. This will make things a whole lot better for awhile, however, it won't necessarily prevent the crack continuing to propagate. Gluing carbon fiber across the crack?MAY restore the structural integrity, but it won't?remove the residual strain at the crack tip. Unfortunately, the initial crack probably transformed a rather broadly curved distortion in the windshield opening into a much more angular one. Adding the carbon fiber reinforcement will reinforce the deformation rather than remove it. Until the deformation is removed or the crack propagates far enough to reduce the strain to an acceptable level, the crack will keep growing. ? It is possible that the crack has already extended far enough to reduce the strain and that drilling the crack tip will arrest the problem, but I doubt it. It will probably continue to propagate some additional distance before the strain is adequately reduced and drilling the crack will be effective. ? I can envision braces being attached to the windshield opening to restore it to its original shape, and thereby removing the residual stress in the plexiglass. You might also be able to reinforce the windshield in front of the crack tip to prevent the distortion from traveling with the crack, but this will probably?impair vision. All of this seems a lot more complicated and involved than just cutting out the windshield and gluing in a replacement. ? Sorry this isn't what you wanted to hear. ? Rob? ? ----------MB_8CB3D753E109608_340_BD4_WEBMAIL-MY01.sysops.aol.com Content-Transfer-Encoding: 7bit Content-Type: text/html; charset="us-ascii" I concur that the method of repair is problematic. Flying with a cracked windshield especially in a pressurized airplane is not recommended. If the window were to fail (worst case) is it would be catastrophic for the pilot and passengers. I know this is not what one would like to hear but the only solution I see here is to remove and replace the windshield.

Best Regards,

Jeff


-----Original Message-----
From: REHBINC <rehbinc@aol.com>
To: lml@lancaironline.net
Sent: Mon, 5 Jan 2009 11:32 am
Subject: [LML] Re: L-IVP Cracked Windshield

Bill,
 
My guess is that a residual stress was introduced when you replaced the brace after the gear failure. This has been acting on the windshield ever since, and along with operational loads, has given you this new crack.
 
Drilling the crack tip will reduce the stress concentration from infinity to some calculable value. This will make things a whole lot better for awhile, however, it won't necessarily prevent the crack continuing to propagate. Gluing carbon fiber across the crack MAY restore the structural integrity, but it won't remove the residual strain at the crack tip. Unfortunately, the initial crack probably transformed a rather broadly curved distortion in the windshield opening into a much more angular one. Adding the carbon fiber reinforcement will reinforce the deformation rather than remove it. Until the deformation is removed or the crack propagates far enough to reduce the strain to an acceptable level, the crack will keep growing.
 
It is possible that the crack has already extended far enough to reduce the strain and that drilling the crack tip will arrest the problem, but I doubt it. It will probably continue to propagate some additional distance before the strain is adequately reduced and drilling the crack will be effective.
 
I can envision braces being attached to the windshield opening to restore it to its original shape, and thereby removing the residual stress in the plexiglass. You might also be able to reinforce the windshield in front of the crack tip to prevent the distortion from traveling with the crack, but this will probably impair vision. All of this seems a lot more complicated and involved than just cutting out the windshield and gluing in a replacement.
 
Sorry this isn't what you wanted to hear.
 
Rob 
 
----------MB_8CB3D753E109608_340_BD4_WEBMAIL-MY01.sysops.aol.com--