X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Wed, 14 Jul 2010 13:37:18 -0400 Message-ID: X-Original-Return-Path: Received: from TX2EHSOBE005.bigfish.com ([65.55.88.13] verified) by logan.com (CommuniGate Pro SMTP 5.3.8) with ESMTPS id 4392069 for lml@lancaironline.net; Tue, 13 Jul 2010 22:18:32 -0400 Received-SPF: pass receiver=logan.com; client-ip=65.55.88.13; envelope-from=rpastusek@htii.com Received: from mail104-tx2-R.bigfish.com (10.9.14.236) by TX2EHSOBE005.bigfish.com (10.9.40.25) with Microsoft SMTP Server id 8.1.340.0; Wed, 14 Jul 2010 02:17:56 +0000 Received: from mail104-tx2 (localhost.localdomain [127.0.0.1]) by mail104-tx2-R.bigfish.com (Postfix) with ESMTP id 1CD2D1B700B4 for ; Wed, 14 Jul 2010 02:17:56 +0000 (UTC) X-SpamScore: -4 X-BigFish: VPS-4(zzace9izz1202hzz186Mz2fh2a8h61h) X-Spam-TCS-SCL: 0:0 Received: from mail104-tx2 (localhost.localdomain [127.0.0.1]) by mail104-tx2 (MessageSwitch) id 1279073874303286_7140; Wed, 14 Jul 2010 02:17:54 +0000 (UTC) Received: from TX2EHSMHS047.bigfish.com (unknown [10.9.14.244]) by mail104-tx2.bigfish.com (Postfix) with ESMTP id 3D5AAA38046 for ; Wed, 14 Jul 2010 02:17:54 +0000 (UTC) Received: from VA3DIAHUB014.RED001.local (65.55.171.153) by TX2EHSMHS047.bigfish.com (10.9.99.147) with Microsoft SMTP Server (TLS) id 14.0.482.44; Wed, 14 Jul 2010 02:17:54 +0000 Received: from VA3DIAXVS171.RED001.local ([172.18.2.196]) by VA3DIAHUB014.RED001.local ([10.32.17.82]) with mapi; Tue, 13 Jul 2010 19:17:54 -0700 From: Robert R Pastusek X-Original-To: Lancair Mailing List X-Original-Date: Tue, 13 Jul 2010 19:17:53 -0700 Subject: Door Window Failure-Lancair IV-P Thread-Topic: Door Window Failure-Lancair IV-P Thread-Index: Acsgn0hyjcvyGQgcSsyWrgHXbQSNgAAAydjAAJTEjTA= X-Original-Message-ID: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-cr-hashedpuzzle: AvK8 A3jC BCE8 BN6f BphI BsWp Dm9u EEIZ EQiY FQVO GMWw HEUE Hhu4 IBYf LdGr MSTN;1;bABtAGwAQABsAGEAbgBjAGEAaQByAG8AbgBsAGkAbgBlAC4AbgBlAHQA;Sosha1_v1;7;{104A88FE-C250-4B7F-A420-014E456F73B0};cgBwAGEAcwB0AHUAcwBlAGsAQABoAHQAaQBpAC4AYwBvAG0A;Wed, 14 Jul 2010 02:04:23 GMT;RABvAG8AcgAgAFcAaQBuAGQAbwB3ACAARgBhAGkAbAB1AHIAZQAtAEwAYQBuAGMAYQBpAHIAIABJAFYALQBQAA== x-cr-puzzleid: {104A88FE-C250-4B7F-A420-014E456F73B0} acceptlanguage: en-US Content-Type: multipart/alternative; boundary="_000_E374BE0180357344BBD396A27A0527F60F2FCE46VA3DIAXVS171RED_" MIME-Version: 1.0 X-Reverse-DNS: smtp801.microsoftonline.com X-Original-Return-Path: rpastusek@htii.com --_000_E374BE0180357344BBD396A27A0527F60F2FCE46VA3DIAXVS171RED_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Gentlemen, After much exchange of ideas and techniques with several of you, I finally = cut into my cabin door this past weekend to replace a cracked window. I dis= covered this crack-only visible by looking at an angle into the sandwich be= tween the inner and outer skins in the upper back corner-during pre-flight.= The crack did not extend into the transparent part of the window. This was= one of the early "fast build" doors from Lancair; purchased in 2004-2005. = I will post a detailed report when I'm done, but thought you'd be intereste= d in what I found to date...I was surprised. As this fault was observed directly opposite a door latch, I assumed it res= ulted from the holes drilled through the Plexi to accommodate the latch. As= the door/window was still intact (not blown out), I was careful to grind a= way carbon from the outside to free the window without further damage so we= could confirm this. As I removed the carbon, I exposed a 4" crack starting= about an inch below the latch and extending toward the top of the door and= around the corner radius. The crack was about =BC" "under" the carbon skin= , and had not progressed to the edge of the Plexi at either end. It did not= originate at the bolt holes, but was generally parallel to the edge of the= Plexi and about =BD" farther from the edge than the bolt holes. The crack = appeared to be caused by forceful flexing of the Plexi parallel to its edge= . I am not a structural engineer, but believe this was caused by one or more = of three possibilities (Clark Still gets credit for suggesting the second o= ne). First hypothesis: the latch exerts a twisting moment on the door frame whe= n closed and the door is pressurized. Possible, but I checked the latch ali= gnment and function carefully during initial installation. All of the latch= es are aligned the same, and work very easily...no binding and no stress up= on opening or closing. They also engage fully, and only very slightly "pull= " on the door frame when going over-center. No other latches showed any dam= age or stress in the area, and one of the forward latches is also bolted wi= th holes drilled through the Plexi. The process of pressurizing is a gradua= l increase in force on the door/window, allowing them to conform-within the= ir stress limits. I therefore believe it unlikely this crack was caused by = the door latch or associated mounting holes in the Plexi. Second hypothesis. The window fracture was caused by taxiing the airplane w= ith the door open, allowing it to flex against the air strut during upswing= s. This is a possibility. Clark Still observed during our travel to Alaska = last summer that I often taxi with the door fully open (I think he's jealou= s because he needs to secure the door to start his IV-P Turbine). I have do= ne this from the first flights, but have always closed, or held the door pa= rtially closed, during any taxi over rough surfaces...and this has been ve= ry infrequent. I don't think this was the cause, but the failure mode I obs= erved in the window was likely caused by door frame flexing that this situa= tion would cause, so it's a possibility. Third hypothesis. Starting with the FB doors, Lancair re-oriented the lift= strut location so that its attach point on the door frame is just above t= he "offending" latch location, and it's mounted to the door stiffener. On a= t least two known occasions, other people have opened the canopy door in th= e wind and allowed the door to extend forcibly against the lift strut inter= nal stop. This would cause a sudden twisting of the door frame in the locat= ion of the crack. Although both violent door openings that I am aware of oc= curred some time ago, I believe this to be the cause of the failure--subjec= t to further review/ideas/comments from you. A couple of related observations. The door was well constructed in the area= s I opened. I found no voids or weak areas. Holes in the Plexi for through-= bolts had been drilled to approximately =BD", filled with Hysol and redrill= ed. All four of them were intact, and these "spacers" quite forcefully held= the inner and outer skins together. The window had been bedded against the= outer skin with Hysol, and bedded with micro around the edges. The window = was well attached to the door skins, although it could be separated with a = thin putty knife. The bond appears to be mechanical-the Hysol adheres by co= nforming very closely to the rough surface without making a chemical or adh= esive attachment. More to follow as I have data... Bill Harrelson and I took a lot of pictures, and I'll take more as we compl= ete this job. I'll write up the details for posting on the LML and LOBO web= sites for those interested. I'd like to extend a special thanks to Laurie = Fitzgerald (Australia), Brent Regan and Brad Simmons for their exceptional = advice, pictures, information-and encouragement. As with most things done o= n this airplane, I'm combining their excellent recommendations to hopefully= make a long-lasting and reliable fix. See you at Oshkosh! Bob --_000_E374BE0180357344BBD396A27A0527F60F2FCE46VA3DIAXVS171RED_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Gentlemen,

 

After much exchange of ideas and techniques with several of = you, I finally cut into my cabin door this past weekend<= span style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'= > to replace a cracked window. I discovered this crack—only visible by loo= king at an angle into the sandwich between the inner and outer skins in the uppe= r back corner—during pre-flight. The crack did not extend into the transparent part of the window. This was one of the early “fast build= ” doors from Lancair; purchased in 2004-2005. I will post a detailed report w= hen I’m done, but thought you’d be interested in what I found to date…I was surprised.

 

As this fault was observed directly opposite a door latch, I assumed it resulted from the holes drilled through the Plexi to accommodate= the latch. As the door/window was still intact (not blown out), I was careful t= o grind away carbon from the outside to free the window without further damag= e so we could confirm this. As I removed the carbon, I exposed a 4” crack starting about an inch below the latch and extending toward the top of the = door and around the corner radius. The crack was about =BC” “under&#= 8221; the carbon skin, and had not progressed to the edge of the Plexi at either = end. It did not originate at the bolt holes, but was generally parallel to the e= dge of the Plexi and about =BD” farther from the edge than the bolt holes= . The crack appeared to be caused by forceful flexing of the Plexi parallel to it= s edge.

 

I am not a structural engineer, but believe this was caused by one or more of three possibilities (Clark Still gets credit for suggesting the second one).

 

First hypothesis:  the latch exerts a twisting moment o= n the door frame when closed and the door is pressurized. Possible, but I che= cked the latch alignment and function carefully during initial installation. All of the latches are aligned the same, and work very easily…no binding = and no stress upon opening or closing. They also engage fully, and only very slightly “pull” on the door frame when going over-center. No ot= her latches showed any damage or stress in the area, and one of the forward lat= ches is also bolted with holes drilled through the Plexi. The process of pressurizing is a gradual increase in force on the door/window, allowing th= em to conform—within their stress limits. I therefore believ= e it unlikely this crack was caused by the door latch or associated mounting hol= es in the Plexi.

 

Second hypothesis. The window fracture was caused by taxiing the airplane with the door open, allowing it to flex agai= nst the air strut during upswings. This is a possibility. Clark Still observed during our travel to Alaska last summer that I often taxi with the door ful= ly open (I think he’s jealous because he needs to secure the door to sta= rt his IV-P Turbine). I have done this from the first flights, but have always closed, or held the door partially closed, during any taxi over rough surfa= ces…and this=A0 has been very infrequent. I don’t think this was the cause, b= ut the failure mode I observed in the window was likely caused by door frame flexi= ng that this situation would cause, so it’s a possibility.

 

Third hypothesis. Starting with the<= span style=3D'font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'= > FB  doors, Lancair re-oriented the lift strut location so that its attach poin= t on the door frame is just above =A0the ”offending” latch location, and it’s mounted to the door stiffener. On at least two known occasions, other people have opened the canopy door in the wind and allowed= the door to extend forcibly against the lift strut internal stop. Th= is would cause a sudden twisting of the door frame in the location of the crac= k. Although both violent door openings that I am aware of occurred some time ago, I believe this to be the cause of the failure--subject to further review/ideas/comments from you.

 

A couple of related observations. The door was well construc= ted in the areas I opened. I found no voids or weak areas. Holes in the Plexi f= or through-bolts had been drilled to approximately =BD”, filled with Hys= ol and redrilled. All four of them were intact, and these “spacers” qu= ite forcefully held the inner and outer skins together. The window had been bed= ded against the outer skin with Hysol, and bedded with micro around the edges. = The window was well attached to the door skins, although it could be separated = with a thin putty knife. The bond appears to be mechanical—the Hysol adher= es by conforming very closely to the rough surface without making a chemical o= r adhesive attachment. More to follow as I have data…=

 

Bill Harrelson and I took a lot of pictures, and I’ll = take more as we complete this job. I’ll write up the details for posting o= n the LML and LOBO web sites for those interested. I’d like to extend a special thanks to Laurie Fitzgerald (Australia), Brent Regan and Brad Simmo= ns for their exceptional advice, pictures, information—and encouragement= . As with most things done on this airplane, I’m combining their excellent recommendations to hopefully make a long-lasting and reliable fix.

 

See you at Oshkosh!

 

Bob

 

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