Return-Path: Received: from [65.54.169.70] (HELO hotmail.com) by logan.com (CommuniGate Pro SMTP 4.2b3) with ESMTP id 90172 for flyrotary@lancaironline.net; Wed, 26 May 2004 00:08:42 -0400 Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Tue, 25 May 2004 20:57:34 -0700 Received: from 4.174.0.58 by bay3-dav40.bay3.hotmail.com with DAV; Wed, 26 May 2004 03:57:34 +0000 X-Originating-IP: [4.174.0.58] X-Originating-Email: [lors01@msn.com] X-Sender: lors01@msn.com From: "Tracy Crook" To: "Rotary motors in aircraft" Subject: Re: [FlyRotary] Fuel Pump Design Date: Tue, 25 May 2004 23:57:30 -0400 MIME-Version: 1.0 X-Mailer: MSN Explorer 7.02.0011.2700 Content-Type: multipart/alternative; boundary="----=_NextPart_001_0000_01C442B4.0A2A5730" Message-ID: X-OriginalArrivalTime: 26 May 2004 03:57:34.0856 (UTC) FILETIME=[93CFE880:01C442D5] ------=_NextPart_001_0000_01C442B4.0A2A5730 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Good point Mark. This sounds like another good argument for the arrangem= ent that I use. Always draw & return to the same tank. Refill from the other tank when n= ecessary using a low pressure facet fuel pump. This eliminates the need = to ever run the tank in use low and risk running dry (unless you are real= ly OUT of gas). No fuel selector needed. Simple plumbing. Only require= s a single return port. Eliminates that nervous moment when you wonder "= Should I switch tanks now or use that last gallon of fuel in the tank & r= isk running dry". =20 Tracy ----- Original Message ----- From: Mark Steitle Sent: Tuesday, May 25, 2004 4:12 PM To: Rotary motors in aircraft Subject: [FlyRotary] Fuel Pump Design Fuel system design hasn't come up in quite a while. But since a large po= rtion of accidents are fuel related, I thought this would be worthy of di= scussion. I have experienced a failure mode during ground runs on my Lancair ES wit= h 20B that seems to be a problem with other types of installations as wel= l. I recently read a first flight report by a professional test pilot, D= avid Allen, that almost had to set a Lancair ES, N711RG, down on I-70 due= to the inability to restart the engine after running a tank dry. (See w= ww.geocities.com/daveandjj for the full story.) This was a certified fue= l-injected engine installation. Also, the Subaru guys (I have been lurki= ng on the Eggenfelder Subie site today) had a similar situation, resultin= g in some glider time and a dead-stick landing. =20 The problem is that after exhausting the fuel in one tank an airlock form= s between the fuel pump(s) and the fuel pressure regulator that the efi p= ump cannot overcome due to lack of fuel in the supply line. This is what= I have experienced with my installation on ground runs. I can't get the= efi pumps to re-prime unless I momentarily break a line loose between th= e pump outlet and the pressure regulator. As soon as I do that the pump = will re-prime and all is well. =20 For the record, I have two of Tracy's efi pumps, with two efi filters, ho= oked in parallel. They are mounted low on the fire wall. Upstream is a = gascolator and an Andair 6-port selector valve. Downstream of the pumps/= filters is a map sensing pressure regulator. There is a -6AN going to th= e fuel rail, and a -4 return line back to the Andair valve/tank. I was curious if anyone else has had this happen and what they did to res= olve the issue. I have come up with two possible solutions. =20 1. Tee off the pump output and put an electric solenoid valve in the lin= e and tee the outlet of the solenoid to the fuel return line, past the re= gulator. Push-button switch on panel would activate the solenoid. If ne= eded, a second or two of activation should relieve the air-lock and allow= the pumps to re-prime. 2. Install a bleed line around the pressure regulator with a small meter= ing orifice (.020-.030") that would bleed off any air that might get trap= ped. (This appears to be the solution the Subaru group is focusing on). = This would be a full time bypass. This seems to be the simpler solution= 3. Install a low pressure, high volume fuel pump in one, or both, of the= wing tanks. Procedure would be to always keep reserve fuel in this tank= =20 Any comments from seasoned flyers would be welcomed. Mark S. =20 ------=_NextPart_001_0000_01C442B4.0A2A5730 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Good point Mar= k.  This sounds like another good argument for the arrangement that = I use.
 
Always draw & return to the same = tank.  Refill from the other tank when necessary using a low pressur= e facet fuel pump.  This eliminates the need to ever run the tank in= use low and risk running dry (unless you are really OUT of gas).  N= o fuel selector needed.  Simple plumbing.  Only requires a sing= le return port.  Eliminates that nervous moment when you wonder "Sho= uld I switch tanks now or use that last gallon of fuel in the tank & = risk running dry". 
 
Tracy
&= nbsp;
----- Original Message -----
From: Mar= k Steitle
Sent: Tuesday, May= 25, 2004 4:12 PM
To: Rotary= motors in aircraft
Subject:= [FlyRotary] Fuel Pump Design
 
Fuel system design h= asn't come up in quite a while.  But since a large portion of accide= nts are fuel related, I thought this would be worthy of discussion.
I have experienced a failure mode during ground runs on my Lancair ES w= ith 20B that seems to be a problem with other types of installations as w= ell.  I recently read a first flight report by a professional test p= ilot, David Allen, that almost had to set a Lancair ES, N711RG, down on I= -70 due to the inability to restart the engine after running a tank dry.&= nbsp; (See www.geocities.com/daveandjj for the full story.)  This was a certified fuel-injected engine in= stallation.  Also, the Subaru guys (I have been lurking on the Eggen= felder Subie site today) had a similar situation, resulting in some glide= r time and a dead-stick landing. 

The problem is that after = exhausting the fuel in one tank an airlock forms between the fuel pump(s)= and the fuel pressure regulator that the efi pump cannot overcome due to= lack of fuel in the supply line.  This is what I have experienced w= ith my installation on ground runs.  I can't get the efi pumps to re= -prime unless I momentarily break a line loose between the pump outlet an= d the pressure regulator.  As soon as I do that the pump will re-pri= me and all is well. 

For the record, I have two of Tracy's e= fi pumps, with two efi filters, hooked in parallel.  They are mounte= d low on the fire wall.  Upstream is a gascolator and an Andair 6-po= rt selector valve.  Downstream of the pumps/filters is a map sensing= pressure regulator.  There is a -6AN going to the fuel rail, and a = -4 return line back to the Andair valve/tank.

I was curious if any= one else has had this happen and what they did to resolve the issue. = ; I have come up with two possible solutions. 

1.  Tee = off the pump output and put an electric solenoid valve in the line and te= e the outlet of the solenoid to the fuel return line, past the regulator.=   Push-button switch on panel would activate the solenoid.  If = needed, a second or two of activation should relieve the air-lock and all= ow the pumps to re-prime.

2.  Install a bleed line around the= pressure regulator with a small metering orifice (.020-.030") that would= bleed off any air that might get trapped.  (This appears to be the = solution the Subaru group is focusing on).  This would be a full tim= e bypass.  This seems to be the simpler solution.

3.  In= stall a low pressure, high volume fuel pump in one, or both, of the wing = tanks.  Procedure would be to always keep reserve fuel in this tank.=  

Any comments from seasoned flyers would be welcomed.
Mark S.
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