Return-Path: Received: from [65.54.169.120] (HELO hotmail.com) by logan.com (CommuniGate Pro SMTP 4.2b5) with ESMTP id 167918 for flyrotary@lancaironline.net; Fri, 18 Jun 2004 15:48:41 -0400 Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Fri, 18 Jun 2004 12:48:11 -0700 Received: from 65.54.98.165 by bay3-dav90.bay3.hotmail.com with DAV; Fri, 18 Jun 2004 19:48:10 +0000 X-Originating-IP: [65.54.98.165] X-Originating-Email: [lors01@msn.com] X-Sender: lors01@msn.com From: "Tracy Crook" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Fuel Delivery - Vapor Lock Date: Fri, 18 Jun 2004 15:47:24 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00CA_01C4554B.8CB33740" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: MSN 9 X-MimeOLE: Produced By MSN MimeOLE V9.00.0013.2101 Seal-Send-Time: Fri, 18 Jun 2004 15:47:24 -0400 Message-ID: X-OriginalArrivalTime: 18 Jun 2004 19:48:11.0272 (UTC) FILETIME=[2FAA9080:01C4556D] This is a multi-part message in MIME format. ------=_NextPart_000_00CA_01C4554B.8CB33740 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Friday, June 18, 2004 1:46 AM Subject: [FlyRotary] Re: Fuel Delivery - Vapor Lock Subject: [FlyRotary] Fuel Delivery - Vapor Lock First, it appears that at least one of the incidents resulted from the = fuel pumps/gas collator/lines getting hot enough to cause vapor lock at = the inlet of the pump(s). The a/c was running mogas at the time of the = engine stoppage. One solution appears to be to shield and cool the = pumps and related plumbing with fresh air. =20 Once this happened, it led to the second shortcoming (I have = experienced this with my 20B installation during ground runs). Once the = system had vapor downstream of the pump(s), the efi pump couldn't force = it past the pressure regulator. This can be the result of either vapor = lock or running a tank dry. Their recommendation here is to install a = bleed orifice (approx. .020") around the pressure regulator. =20 Now, the Subie guys are contemplating a re-design of their fuel = systems. I'm wondering now if I should make any changes to my fuel = system (2 wing tanks, 6-port Andair valve, dual EFI pumps mounted on = f/w)? Comments would be welcome, especially from those that have been = flying for a while. Mark S. Clearly this is an important issue and warrants critical review in = anyone's plane. It seemed to me there are some basic considerations; = somewhat dictated by the airplane design. I haven't been flying yet but = my thoughts on designing the system incorporate these;=20 1.. Minimize the potential for pressure drop upstream of the pump. = If you are pumping from a sump tank, don't pump off the bottom, and have = a sump drain there to take care of any water, and have a relatively = coarse screen at the exit from the main tank to take out anything that = you don't want going through the pump. Skip the gascolator upstream. = Put your 10-30 micron filter downstream from the pump.=20 2.. Have the pump at a low point; i.e., in a position of always = having positive pressure, maybe a foot or two of head if possible, and = where any air or vapor bubble will migrate back toward the tank when the = flow is stopped. If there is fuel at the inlet or in the pump there is = no problem having it force any air or vapor downstream through the = pressure regulator. Don't expect the pump to ever have to "suck" the = fuel uphill.=20 3.. Have the pumps and filter in a relatively cool place. I don't = particularly like having fuel in the cabin, but at the bottom of the = firewall is a "cool" place, and some airflow over them couldn't hurt.=20 Hopefully this will keep me from having any problems. We'll see. Al Al always comes up with solid & sensible advice and I would second = most everything he said here. I don't have Al's aversion to fuel = plumbing in the cockpit however. I like it there because I know it's = "cool" and Laura's nose will tell me in an instant if it has the tiniest = of leaks. "Cool" at the bottom of the firewall depends on the = airplane. That is the hottest spot under the cowl on mine. =20 Tracy ------=_NextPart_000_00CA_01C4554B.8CB33740 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
----- Original Message -----
From: Al Gietzen
To: Rotary motors in = aircraft
Sent: Friday, June 18, 2004 = 1:46 AM
Subject: [FlyRotary] Re: Fuel = Delivery -=20 Vapor Lock

Subject:=20 [FlyRotary] Fuel Delivery - Vapor Lock

 


First, it appears that at = least one=20 of the incidents resulted from the fuel pumps/gas collator/lines = getting hot=20 enough to cause vapor lock at the inlet of the pump(s).  The a/c = was=20 running mogas at the time of the engine stoppage.  One solution = appears=20 to be to shield and cool the pumps and related plumbing with fresh = air. =20

Once this happened, it led to the second shortcoming (I have=20 experienced this with my 20B installation during ground runs).  = Once the=20 system had vapor downstream of the pump(s), the efi pump couldn't = force it=20 past the pressure regulator.  This can be the result of either = vapor lock=20 or running a tank dry.  Their recommendation here is to install a = bleed=20 orifice (approx. .020") around the pressure regulator.  =

Now, the=20 Subie guys are contemplating a re-design of their fuel systems.  = I'm=20 wondering now if I should make any changes to my fuel system (2 wing = tanks,=20 6-port Andair valve, dual EFI pumps mounted on f/w)?  Comments = would be=20 welcome, especially from those that have been flying for a = while.

Mark=20 S.

Clearly = this is an=20 important issue and warrants critical review in anyone=92s = plane.  It=20 seemed to me there are some basic considerations; somewhat dictated by = the=20 airplane design.  I haven=92t been flying yet but my thoughts on = designing=20 the system incorporate these;

  1. Minimize the=20 potential for pressure drop upstream of the pump.  If you are = pumping=20 from a sump tank, don=92t pump off the bottom, and have a sump drain = there to=20 take care of any water, and have a relatively coarse screen at the = exit from=20 the main tank to take out anything that you don=92t want going = through the=20 pump.  Skip the gascolator upstream. Put your 10-30 micron = filter=20 downstream from the pump.=20
  2. Have = the pump at=20 a low point; i.e., in a position of always having positive pressure, = maybe a=20 foot or two of head if possible, and where any air or vapor bubble = will=20 migrate back toward the tank when the flow is stopped.  If = there is=20 fuel at the inlet or in the pump there is no problem having it force = any air=20 or vapor downstream through the pressure regulator.  Don=92t = expect the=20 pump to ever have to =93suck=94 the fuel uphill.=20
  3. Have = the pumps=20 and filter in a relatively cool place.  I don=92t particularly = like=20 having fuel in the cabin, but at the bottom of the firewall is a = =93cool=94=20 place, and some airflow over them couldn=92t hurt. =

 

Hopefully = this will=20 keep me from having any problems.  We=92ll see.

 

Al

 Al always comes up with = solid &=20 sensible advice and I would second most everything he said = here.   I=20 don't have Al's aversion to fuel plumbing in the cockpit = however.  I=20 like it there because I know it's "cool" and Laura's nose will tell me = in an=20 instant if it has the tiniest of leaks.   "Cool" = at the=20 bottom of the firewall depends on the airplane.  That is the = hottest spot=20 under the cowl on mine.  

 

Tracy

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