X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 04 Jan 2011 14:07:50 -0500 Message-ID: X-Original-Return-Path: Received: from imr-ma01.mx.aol.com ([64.12.206.39] verified) by logan.com (CommuniGate Pro SMTP 5.3.11) with ESMTP id 4663438 for lml@lancaironline.net; Tue, 04 Jan 2011 09:42:17 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.12.206.39; envelope-from=MikeEasley@aol.com Received: from mtaomg-da04.r1000.mx.aol.com (mtaomg-da04.r1000.mx.aol.com [172.29.51.140]) by imr-ma01.mx.aol.com (8.14.1/8.14.1) with ESMTP id p04EfTxh013094 for ; Tue, 4 Jan 2011 09:41:29 -0500 Received: from core-mkb004c.r1000.mail.aol.com (core-mkb004.r1000.mail.aol.com [172.29.98.13]) by mtaomg-da04.r1000.mx.aol.com (OMAG/Core Interface) with ESMTP id E9F72E0000B0 for ; Tue, 4 Jan 2011 09:41:28 -0500 (EST) From: MikeEasley@aol.com X-Original-Message-ID: <93839.4b2d7f10.3a548b98@aol.com> X-Original-Date: Tue, 4 Jan 2011 09:41:28 -0500 (EST) Subject: Re: [LML] Re: Fuel Dumping X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_93839.4b2d7f10.3a548b98_boundary" X-Mailer: AOL 9.5 sub 5401 X-AOL-IP: 75.71.55.189 X-Originating-IP: [172.29.122.22] x-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:345219392:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d338c4d2331982ef3 --part1_93839.4b2d7f10.3a548b98_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit I've had a discussion with other builders where we compared the added safety some modification weighed against the increased risk of that modification. Adding a 3" hole in your fuel tanks, even with a very reliable valve, certainly adds a potential failure point in a critical system. Mike Easley Colorado Springs In a message dated 1/3/2011 12:22:15 P.M. Mountain Standard Time, MikeEasley@aol.com writes: It seems that the nature of the fuel tank failure would determine whether you need to dump fuel or not to prevent a fire. Do Lancairs have fuel tank ruptures (big hole) or wing separation (small hole) in an off airport landing/crash? If the wing separated, you'd have a small 3/4" hole leaking fuel which would be a much smaller fire than a wing that breaks into the fuel bay and dumps most of the fuel instantly. I'm sure each model of Lancair has different wing structural characteristics that affect how vulnerable the fuel bays are in a crash. The ES has its main spar aft of the fuel bay. The forward spar extends to the outboard rib of the fuel bay (standard 92 gals. fuel). That seems to protect the fuel bay somewhat if you caught a wingtip and ripped off the wing outboard section. I know a lot of the IV guys have fuel in every nook and cranny available in the wings which makes the fuel bays much more susceptible to failure in a crash. Mike Easley Colorado Springs In a message dated 1/3/2011 6:36:15 A.M. Mountain Standard Time, rwolf99@aol.com writes: The only reason I'm aware of why designers include a fuel dump capability is when they design a landing gear system which cannot handle the maxmum takeoff gross weight. This is often the cse on large jets -- think of an airliner which may have a gross weight double that of its typical landing weight. In this case, a landing required immediately after takeoff would require a fuel dump, which could easily be a 15 minute process. I know of no cases where designers include a fuel dump provision to reduce post crash fires. That's not to say the idea is without merit, but I would not bother with it. Instead, I would take measures to prevent inadvertent fuel release after a survivable crash. I'm not sure how to do that -- would a flexible fuel line (say, steel braided) be less likely to tear than a hard aluminum line? Would a silicone fireproofed fuel line be less likely to rupture (those puppies look pretty indestructible)? What about a header tank -- I imagine that five gallons of fuel just above your knees is not a good place for a fuel leak (and yes, my airplane has the header tank). But dumping the fuel before an off-airport landing? I don't think I would do that, but that's just me. - Rob Wolf p.s. the NASA test in the early 1980's involved a remotely-piloted Convair 720 with an anti-misting additive in the fuel. As I recall, the remotely piloted airplane did not hit the intended point on laning and thus the objects intended to puncture the tanks, well, ithey pretty much ripped the wings apart, releasing the fuel all at once. This was a test failure and the explosion-inhibiting anti-mist additive was not adequately tested. Needless to say, they did not repeat the test. _http://en.wikipedia.org/wiki/Controlled_Impact_Demonstration_ (http://en.wikipedia.org/wiki/Controlled_Impact_Demonstration) --part1_93839.4b2d7f10.3a548b98_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
I've had a discussion with other builders where we compared the a= dded=20 safety some modification weighed against the increased risk of that=20 modification.  Adding a 3" hole in your fuel tanks, even with a very= =20 reliable valve, certainly adds a potential failure point in a critical=20 system.
 
Mike Easley
Colorado Springs
 
In a message dated 1/3/2011 12:22:15 P.M. Mountain Standard Time,=20 MikeEasley@aol.com writes:
It seems that the nature of the fuel tank failure would determine wh= ether=20 you need to dump fuel or not to prevent a fire.  Do Lancairs have fu= el=20 tank ruptures (big hole) or wing separation (small hole) in an off airpor= t=20 landing/crash?  If the wing separated, you'd have a small 3/4" hole= =20 leaking fuel which would be a much smaller fire than a wing that breaks i= nto=20 the fuel bay and dumps most of the fuel instantly.
 
I'm sure each model of Lancair has different wing structural=20 characteristics that affect how vulnerable the fuel bays are in= a=20 crash.  The ES has its main spar aft of the fuel bay.  The forw= ard=20 spar extends to the outboard rib of the fuel bay (standard 92 gals.=20 fuel).  That seems to protect the fuel bay somewhat if you caught a= =20 wingtip and ripped off the wing outboard section.  I know a lot of t= he IV=20 guys have fuel in every nook and cranny available in the wings which make= s the=20 fuel bays much more susceptible to failure in a crash.
 
Mike Easley
Colorado Springs
 
In a message dated 1/3/2011 6:36:15 A.M. Mountain Standard Time,=20 rwolf99@aol.com writes:
The only reason I'm aware of why designers include a fuel dump=20 capability is when they design a landing gear system which cannot handl= e the=20 maxmum takeoff gross weight.  This is often the cse on large jets = --=20 think of an airliner which may have a gross weight double that of = its=20 typical landing weight.  In this case, a landing required immediat= ely=20 after takeoff would require a fuel dump, which could easily be a 15 min= ute=20 process.
 
I know of no cases where designers include a fuel dump provision t= o=20 reduce post crash fires.  That's not to say the idea is without me= rit,=20 but I would not bother with it.  Instead, I would take measures to= =20 prevent inadvertent fuel release after a survivable crash.  I'm no= t=20 sure how to do that -- would a flexible fuel line (say, steel brai= ded)=20 be less likely to tear than a hard aluminum line?  Would a silicon= e=20 fireproofed fuel line be less likely to rupture (those puppies look pre= tty=20 indestructible)?  What about a header tank -- I imagine that five= =20 gallons of fuel just above your knees is not a good place for a fuel le= ak=20 (and yes, my airplane has the header tank).
 
But dumping the fuel before an off-airport landing?  I don't = think=20 I would do that, but that's just me.
 
- Rob Wolf
 
p.s. the NASA test in the early 1980's involved a remotely-piloted= =20 Convair 720 with an anti-misting additive in the fuel.  As I recal= l,=20 the remotely piloted airplane did not hit the intended point on laning = and=20 thus the objects intended to puncture the tanks, well, ithey pretty muc= h=20 ripped the wings apart, releasing the fuel all at once.  This was = a=20 test failure and the explosion-inhibiting anti-mist additive was not=20 adequately tested.  Needless to say, they did not repeat the=20 test.
 
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