Return-Path: Received: from [206.46.252.42] (HELO vms042pub.verizon.net) by logan.com (CommuniGate Pro SMTP 4.3c2) with ESMTP id 758533 for flyrotary@lancaironline.net; Thu, 24 Feb 2005 23:20:20 -0500 Received: from verizon.net ([4.12.145.173]) by vms042.mailsrvcs.net (Sun Java System Messaging Server 6.2 HotFix 0.04 (built Dec 24 2004)) with ESMTPA id <0ICG00LIA9DMKK21@vms042.mailsrvcs.net> for flyrotary@lancaironline.net; Thu, 24 Feb 2005 22:20:10 -0600 (CST) Date: Thu, 24 Feb 2005 23:20:09 -0500 From: Finn Lassen Subject: Re: [FlyRotary] Re: Vapor Lock In-reply-to: To: Rotary motors in aircraft Message-id: <421EA779.5010906@verizon.net> MIME-version: 1.0 Content-type: multipart/alternative; boundary="Boundary_(ID_ypNs3nWZ6CXEqpaEq7WS6A)" X-Accept-Language: en-us, en References: User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.4) Gecko/20030624 Netscape/7.1 (ax; PROMO) This is a multi-part message in MIME format. --Boundary_(ID_ypNs3nWZ6CXEqpaEq7WS6A) Content-type: text/plain; charset=windows-1252; format=flowed Content-transfer-encoding: 7BIT The Cessna 152/172 have, what, 2 - 3 feet of gravity feed, you have only one. Anyway, here's a question. Is there a possibility that the path from the lagging tank gets hotter than the faster draining tank? I'm beginning to think that even a minor temp rise in fuel path to pumps produces a much bigger effect than any of us would imagine. Just a theory not proven yet. Finn Jim Sower wrote: > This problem drove me NUTS for two years. I tried everything. For > example, I checked the vents as best I could, leveled the airplane > (checked the ball to ensure it was centered - it was), disconnected > the fuel line from the engine side of the firewall and let it drain > into a bucket. I turned off one strake at a time (with manual > maintenance valve) and timed how long it took for the other strake to > gravity drain ten gal of fuel into the sump, out of the sump through > the boost pump, through the filter and then through the firewall into > the bucket(s). Then I turned it off and did the same thing with the > left tank. They both drained 10 gal each within 5% of the same > time. Then I reconnected all the plumbing, taped over the fuel caps > so there's no possible way they could leak and went flying. Right > tank drained 20 gal while the left tank maybe 2 or 3. Level balanced > flight on a cross country. All fuel lines, vent lines, etc. are as > identical as I am able to make them. To this day, I've not met > anybody who can explain what happened. I tried everything. Back and > forth on the Velocity list much longer than you've been inquiring > after your vapor lock. NOTHING. I figured out a workaround - I > installed electric shutoff valves in place of the manual maintenance > valves between the strake and the sump. Now, when one tank doesn't > transfer, I turn off the tank that does and let the "reluctant" tank > catch up. The pump sucks it through the system just fine (the head > pressure of 6" of fuel is about 0.16 psi - a problem that would > inhibit that flow you can't even MEASURE. Assymmetric transfer is > common as dirt in the Velocity community (but not nearly as persistent > as mine). It was also a problem a long time with the Vari-EZ. > > > --Boundary_(ID_ypNs3nWZ6CXEqpaEq7WS6A) Content-type: text/html; charset=windows-1252 Content-transfer-encoding: 8BIT The Cessna 152/172 have, what, 2 - 3 feet of gravity feed, you have only one.

Anyway, here's a question. Is there a possibility that the path from the lagging tank gets hotter than the faster draining tank? I'm beginning to think that even a minor temp rise in fuel path to pumps produces a much bigger effect than any of us would imagine. Just a theory not proven yet.

Finn

Jim Sower wrote:

This problem drove me NUTS for two years. I tried everything. For example, I checked the vents as best I could, leveled the airplane (checked the ball to ensure it was centered - it was), disconnected the fuel line from the engine side of the firewall and let it drain into a bucket. I turned off one strake at a time (with manual maintenance valve) and timed how long it took for the other strake to gravity drain ten gal of fuel into the sump, out of the sump through the boost pump, through the filter and then through the firewall into the bucket(s). Then I turned it off and did the same thing with the left tank. They both drained 10 gal each within 5% of the same time. Then I reconnected all the plumbing, taped over the fuel caps so there's no possible way they could leak and went flying. Right tank drained 20 gal while the left tank maybe 2 or 3. Level balanced flight on a cross country. All fuel lines, vent lines, etc. are as identical as I am able to make them. To this day, I've not met anybody who can explain what happened. I tried everything. Back and forth on the Velocity list much longer than you've been inquiring after your vapor lock. NOTHING. I figured out a workaround - I installed electric shutoff valves in place of the manual maintenance valves between the strake and the sump. Now, when one tank doesn't transfer, I turn off the tank that does and let the "reluctant" tank catch up. The pump sucks it through the system just fine (the head pressure of 6" of fuel is about 0.16 psi - a problem that would inhibit that flow you can't even MEASURE. Assymmetric transfer is common as dirt in the Velocity community (but not nearly as persistent as mine). It was also a problem a long time with the Vari-EZ.
  

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