X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml Date: Fri, 18 Aug 2006 05:21:36 -0400 Message-ID: X-Original-Return-Path: Received: from [64.12.137.4] (HELO imo-m23.mail.aol.com) by logan.com (CommuniGate Pro SMTP 5.1c.3) with ESMTP id 1336434 for lml@lancaironline.net; Thu, 17 Aug 2006 23:50:19 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.137.4; envelope-from=Sky2high@aol.com Received: from Sky2high@aol.com by imo-m23.mx.aol.com (mail_out_v38_r7.6.) id q.3f7.8941dbd (29678) for ; Thu, 17 Aug 2006 23:49:39 -0400 (EDT) From: Sky2high@aol.com X-Original-Message-ID: <3f7.8941dbd.321692d3@aol.com> X-Original-Date: Thu, 17 Aug 2006 23:49:39 EDT Subject: Re: [LML] Lancair 4PT fuel system seems dangerous to me... help X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1155872979" X-Mailer: 9.0 Security Edition for Windows sub 5330 X-Spam-Flag: NO -------------------------------1155872979 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 8/17/2006 9:41:21 P.M. Central Standard Time, sysder@gmail.com writes: I was looking at a friends Lancair 4PT the other day and what I found really scared me. Seems that Lancair is telling builders to use the belly tank as a header tank, and there is a vent that has an solenoid (electric) that is closed when the master is switched on. The theory seems to be that when the plane is refueled, the master is off and therefore solenoid open and any air in the system can escape at that time. First, it is ridiculas to use a belly tank as a primary tank on one of these little planes. This means that the belly will always be the tank to have the last bit of fuel in the plane. It is completely dangerous to do this simply because of a potential gear up landing intentional or not...... Second, it seems to me that when the plane is low on fuel, clearly there is the potential of air getting into the belly tank when either wing gets low. These planes can climb really aggressivly. When this happens, the fuel rolls aft, and now the pump can pull air. It is completely non-standard to gravity feed fuel in a low wing aircraft. On a turbine aircraft,,, No way. I don't even want to think about what would happen if this little electic solenoid would fail... If it didn't close, the electic fuel pump will have a much easier time pulling air than fuel... I can't imagine that there haven't been failures of this sort already. I am suggesting to him that there be a way to purge air from the fuel system all the time. Also, he should use the fuel in the belly first, and use it completely. A simple selector valve would take care of this. Some selectors even have a return line built into them for injected piston engines that need it. You should have a return to a vented wing. Another way would be to pump the belly to a wing, as needed. Maybe a small header tank after the electric fuel pump, with a reduced fitting on the top for a return to purge any air in the system. A reduced fitting will keep the pressure up but also purge any air back to a vent wing. I find it difficult to believe Lancair would endorse such a fuel system as it stands now. It would never pass an FAA system check. They must have never run this past a FAA system DER. I certainly hope the insurance company's that underwrite these planes never hear about this. Seems to me just a flameout waiting to happen. Please anyone tell me where my mis guidance is..... Bill McDonald Sys DER Big airplanes Bill, Welcome to the list. Let's look at the whole picture - While low wing aircraft carrying fuel are at risk in any gear up landing, belly fuel doesn't necessarily increase the risk - if it rips open during the slide, the fuel will escape before coming to rest. Maybe. Another view is that the belly is merely a large sump for the wing tanks, ideally located at the lowest point so that all the wing fuel can be utilized during level coordinated flight. Properly baffled, the belly should deliver almost all of the fuel aboard and is kept filled via gravity and positive pressure supplied by the wing tank vents - simple, no? No slosh compartments are necessary in the wings and no selector valves that seem to be a root of so many fuel management accidents. Of course, this requires that the vents be operational only in the wing tanks in flight since an unbalanced flight pressurized vent in the belly could force the fuel back into the wings, could it not? Even check valves might stop the reverse flow, but the belly vent pressure could be working against the gravity flow. If the wings had a greater pressure (gravity plus vent) than the belly vent, fuel could be forced out the belly vent - well maybe a check valve could stop that too. Of course, everybody checks their well baffled belly tank for the minimum fuel required in a slip,skid, climb or descent so that the fuel intake would not become unported. See, the pump should only pull air if there is not enough fuel in the entire plane. You have interesting ideas. However, the system ,as originally outlined, should have no problem passing the requirements for an Experimental, Amateur Built airworthiness certificate as determined by an FAA inspector or DAR. As an experimental aircraft, the builder can obtain good solenoids as opposed to those TSO'd in 1938 - you know, the ones that you expect to fail because of your experience. Scott Krueger AKA Grayhawk Lancair N92EX IO320 SB 89/96 Aurora, IL (KARR) -------------------------------1155872979 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
In a message dated 8/17/2006 9:41:21 P.M. Central Standard Time,=20 sysder@gmail.com writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>
I was looking at a friends Lancair 4PT the other day and what I=20 found really scared me.
Seems that Lancair is telling builders to use the belly tank as a hea= der=20 tank, and there is
a vent that has an solenoid (electric) that is closed when the master= is=20 switched on.
The theory seems to be that when the plane is refueled, the master is= off=20 and therefore solenoid open and any
air in the system can escape at that time.
 
First, it is ridiculas to use a belly tank as a primary tank on one o= f=20 these little planes.
This means that the belly will always be the tank to have the last bi= t of=20 fuel in the plane.
It is completely dangerous to do this simply=20 because of a potential gear up landing  intentional or=20 not...... 
 
Second, it seems to me that when the plane is low on=20 fuel, clearly there is the potential
of air getting into the belly tank when either wing gets=20 low. 
These planes can climb really aggressivly. When this=20 happens, the fuel rolls aft, and
now the pump can pull air.  
 
It is completely non-standard to gravity feed fuel in a low wing=20 aircraft.
On a turbine aircraft,,, No way.
 
I don't even want to think about what would happen if this little ele= ctic=20 solenoid would
fail... If it didn't close, the electic fuel pump will have a much ea= sier=20 time pulling air than fuel...
 
I can't imagine that there haven't been failures of this sort=20 already.
 
I am suggesting to him that there be a way to purge air from the fuel= =20 system all the time.
Also, he should use the fuel in the belly first, and use it completel= y. A=20 simple selector valve
would take care of this. Some selectors even have a return line built= =20 into them for injected piston engines that need
it. You should have a return to a vented wing.
Another way would be to pump the belly to a wing, as needed.
 
Maybe a small header tank after the electric fuel pump, with a reduce= d=20 fitting on the top for a return to purge any air in the system.=20
A reduced fitting will keep the pressure up but also purge any air ba= ck=20 to a vent wing.
 
I find it difficult to believe Lancair would endorse such a fuel syst= em=20 as it stands now.
It would never pass an FAA system check. They must have never run thi= s=20 past a FAA system DER.
I certainly hope the insurance company's that underwrite these planes= =20 never hear about this.
Seems to me just a flameout waiting to happen.
Please anyone tell me where my mis guidance is.....
 
Bill McDonald
Sys DER
Big airplanes
Bill,
 
Welcome to the list.
 
Let's look at the  whole picture - While low wing aircraft carryin= g=20 fuel are at risk in any gear up landing, belly fuel doesn't necessarily= =20 increase the risk - if it rips open during the slide, the fuel will escape=20 before coming to rest.  Maybe.
 
Another view is that the belly is merely a large sump for the wing tank= s,=20 ideally located at the lowest point so that all the wing fuel can be utilize= d=20 during level coordinated flight.  Properly baffled, the belly shou= ld=20 deliver almost all of the fuel aboard and is kept filled via gravity and=20 positive pressure supplied by the wing tank vents - simple, no?&nb= sp;=20
 
No slosh compartments are necessary in the wings and no selector valves= =20 that seem to be a root of so many fuel management accidents.  Of course= ,=20 this requires that the vents be operational only in the wing tanks= in=20 flight since an unbalanced flight pressurized vent in the belly co= uld=20 force the fuel back into the wings, could it not? Even check valves mig= ht=20 stop the reverse flow, but the belly vent pressure could be working aga= inst=20 the gravity flow.  If the wings had a greater pressure (gravity plus ve= nt)=20 than the belly vent, fuel could be forced out the belly vent - well maybe a=20 check valve could stop that too.  Of course, everybody checks their=20 well baffled belly tank for the minimum fuel required in a slip,skid, c= limb=20 or descent so that the fuel intake would not become unported.  See= ,=20 the pump should only pull air if there is not enough fuel in the entire=20 plane.
 
You have interesting ideas.  However, the system ,as originally=20 outlined, should have no problem passing the requirements for an Experimenta= l,=20 Amateur Built airworthiness certificate as determined by an FAA inspector or= =20 DAR.  As an experimental aircraft, the builder can obtain good solenoid= s as=20 opposed to those TSO'd in 1938 - you know, the ones that you expect=20 to fail because of your experience.=20
 
Scott Krueger=20 AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL (KARR)

 
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