Return-Path: Received: from imf20aec.mail.bellsouth.net ([205.152.59.68] verified) by logan.com (CommuniGate Pro SMTP 4.3c1) with ESMTP id 725338 for flyrotary@lancaironline.net; Fri, 11 Feb 2005 14:09:58 -0500 Received-SPF: pass receiver=logan.com; client-ip=205.152.59.68; envelope-from=sqpilot@bellsouth.net Received: from [209.214.45.60] by imf20aec.mail.bellsouth.net (InterMail vM.5.01.06.11 201-253-122-130-111-20040605) with ESMTP id <20050211190906.SYOD1977.imf20aec.mail.bellsouth.net@[209.214.45.60]> for ; Fri, 11 Feb 2005 14:09:06 -0500 Received: from 127.0.0.1 (AVG SMTP 7.0.300 [265.8.7]); Fri, 11 Feb 2005 13:08:57 -0600 Message-ID: <020601c5106d$211d1180$3c2dd6d1@paul52u7f5qyav> From: "Paul" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Vapor lock - bypass bleed Date: Fri, 11 Feb 2005 13:08:54 -0600 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="=======AVGMAIL-420D02C9340D=======" --=======AVGMAIL-420D02C9340D======= Content-Type: multipart/alternative; boundary="----=_NextPart_000_0203_01C5103A.D65A31F0" ------=_NextPart_000_0203_01C5103A.D65A31F0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable ----- Original Message -----=20 From: Mark R Steitle=20 To: Rotary motors in aircraft=20 Sent: Thursday, February 10, 2005 10:15 AM Subject: [FlyRotary] Re: Vapor lock - bypass bleed =20 =20 -------------------------------------------------------------------------= ----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] = On Behalf Of Al Gietzen Sent: Thursday, February 10, 2005 9:49 AM To: Rotary motors in aircraft Subject: [FlyRotary] Vapor lock - bypass bleed =20 Al,=20 What happens if the lines in the engine bay and fuel pumps get hot = enough for the fuel to boil inside them? Are the pumps still going to = produce enough pressure to function normally? My guess is no. Paul = said his coolant temp was 210+. He had been doing extended ground runs = followed by some taxiing, which would allow for lots of heat soak and = little cooling air. I imagine the fuel pumps and lines were pretty = warm. Maybe warm enough to cause vapor lock. =20 Mark; =20 I agree that the issue of potential vapor lock warrants careful = attention; and that a downstream bleed may be a necessary precaution = depending on the system design and pump location. I'd think that if you = have fuel boiling in the line and pump you have already made a mistake = in the configuration, and in that extreme case the small bleed line = isn't likely to solve the problem.=20 =20 IMO; it is important that there be minimum pressure drop upstream from = the pump - no more than can be overcome by the pressure head bringing = the fuel there; minimum heating of the fuel before getting to the pump; = and, if at all possible, that the pump be at a low point where air can = move back up stream. Because of its low surface tension, fuel will flow = past a bubble in a -6 (3/8") line, so there can be self priming. If the pump is on the engine side of the firewall, it should be = shielded and insulated; the feed line length on the engine side of the = firewall should be kept short and insulated (at least firesleeved). If = the sump or header tank is less than couple of gallons, fuel returned = from the pressure regulator should go back to the main tank or through a = cooler. With these precautions the line and pump will be kept cool by = the flow of fuel. =20 Under the circumstances that Paul describes, vapor lock would have to = be considered a possibility. =20 Al =20 Al, I totally agree, and this has been my approach (keep things cool, = return fuel to tank, etc.). One point of clarification concerning the = purpose of the air bleed. The closer the pump is to the fuel supply, = the less need for the bleed circuit. Initially, my pumps were mounted = on the firewall, about 8 feet from the tank. I have since moved the = boost pump closer and in the process was able to lower it significantly. = My only suggestion is that we check our fuel systems to verify that the = efi pump(s) are able to re-prime if/when we run a tank dry. That is = where I found a problem with my installation. The bleeder circuit fixed = that nasty little problem. =20 =20 Mark =20 =20 Very helpful information, gentlemen....my fuel pumps are 8 inches from = the sump tank. My fuel lines, however are not insulated or wrapped in = firesleeve. That will be corrected ASAP. Thank you. Paul Conner -------------------------------------------------------------------------= ----- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 265.8.7 - Release Date: 2/10/2005 ------=_NextPart_000_0203_01C5103A.D65A31F0 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
 
----- Original Message -----
From:=20 Mark R Steitle =
Sent: Thursday, February 10, = 2005 10:15=20 AM
Subject: [FlyRotary] Re: Vapor = lock -=20 bypass bleed

 

 

From: Rotary=20 motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Al = Gietzen
Sent: Thursday, February 10, = 2005 9:49=20 AM
To: Rotary = motors in=20 aircraft
Subject: = [FlyRotary]=20 Vapor lock - bypass bleed

 

Al,=20

What=20 happens if the lines in the engine bay and fuel pumps get hot enough = for the=20 fuel to boil inside them?  Are the pumps still going to produce = enough=20 pressure to function normally?  My guess is no.   Paul = said his=20 coolant temp was 210+.  He had been doing extended ground runs = followed=20 by some taxiing, which would allow for lots of heat soak and little = cooling=20 air.  I imagine the fuel pumps and lines were pretty warm.  = Maybe=20 warm enough to cause vapor lock. =20     

Mark;

 

I agree = that the=20 issue of potential vapor lock warrants careful attention; and that a=20 downstream bleed may be a necessary precaution depending on the system = design=20 and pump location.  I=92d think that if you have fuel boiling in = the line=20 and pump you have already made a mistake in the configuration, and in = that=20 extreme case the small bleed line isn=92t likely to solve the problem. =

 

IMO; it = is=20 important that there be minimum pressure drop upstream from the pump = =96 no more=20 than can be overcome by the pressure head bringing the fuel there; = minimum=20 heating of the fuel before getting to the pump; and, if at all = possible, that=20 the pump be at a low point where air can move back up stream.  = Because of=20 its low surface tension, fuel will flow past a bubble in a -6 (3/8=94) = line, so=20 there can be self priming.

If the = pump is on=20 the engine side of the firewall, it should be shielded and insulated; = the feed=20 line length on the engine side of the firewall should be kept short = and=20 insulated (at least firesleeved).  If the sump or header tank is = less=20 than couple of gallons, fuel returned from the pressure regulator = should go=20 back to the main tank or through a cooler.  With these = precautions the=20 line and pump will be kept cool by the flow of=20 fuel.

 

Under the = circumstances that Paul describes, vapor lock would have to be = considered a=20 possibility.

 

Al

 

Al,

I totally = agree, and=20 this has been my approach (keep things cool, return fuel to tank, = etc.). =20 One point of clarification concerning the purpose of the air = bleed.  The=20 closer the pump is to the fuel supply, the less need for the bleed=20 circuit.  Initially, my pumps were mounted on the firewall, about = 8 feet=20 from the tank.  I have since moved the boost pump closer and in = the=20 process was able to lower it significantly.  My only suggestion = is that=20 we check our fuel systems to verify that the efi pump(s) are able to = re-prime=20 if/when we run a tank dry.  That is where I found a problem with = my=20 installation.  The bleeder circuit fixed that nasty little = problem. =20

 

Mark =20

    

Very = helpful=20 information, gentlemen....my fuel pumps are 8 inches from the sump = tank. =20 My fuel lines, however are not insulated or wrapped in = firesleeve.  That=20 will be corrected ASAP.  Thank you.  Paul Conner

No virus found in this incoming message.
Checked by AVG=20 Anti-Virus.
Version: 7.0.300 / Virus Database: 265.8.7 - Release = Date:=20 2/10/2005
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