X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 23 May 2011 08:03:10 -0400 Message-ID: X-Original-Return-Path: Received: from imr-db02.mx.aol.com ([205.188.91.96] verified) by logan.com (CommuniGate Pro SMTP 5.4c3j) with ESMTP id 4989585 for lml@lancaironline.net; Fri, 20 May 2011 09:30:17 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.91.96; envelope-from=MikeEasley@aol.com Received: from mtaomg-mb04.r1000.mx.aol.com (mtaomg-mb04.r1000.mx.aol.com [172.29.41.75]) by imr-db02.mx.aol.com (8.14.1/8.14.1) with ESMTP id p4KDTZ44012842 for ; Fri, 20 May 2011 09:29:35 -0400 Received: from core-mka002c.r1000.mail.aol.com (core-mka002.r1000.mail.aol.com [172.29.102.70]) by mtaomg-mb04.r1000.mx.aol.com (OMAG/Core Interface) with ESMTP id 52949E000087 for ; Fri, 20 May 2011 09:29:35 -0400 (EDT) From: MikeEasley@aol.com X-Original-Message-ID: <36827.7f93daf2.3b07c6bf@aol.com> X-Original-Date: Fri, 20 May 2011 09:29:35 -0400 (EDT) Subject: Re: [LML] Re: Fuel restriction or air, Fuel Vent Check Valves X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_36827.7f93daf2.3b07c6bf_boundary" X-Mailer: AOL 9.6 sub 5001 X-AOL-IP: 75.71.55.189 X-Originating-IP: [75.71.55.189] x-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:453844320:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d294b4dd66cbf42d9 --part1_36827.7f93daf2.3b07c6bf_boundary Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en Colyn, =20 The ES has tiny NACA scoops in the wingtips like the IV with the thought= =20 that they would slightly pressurize the fuel tanks to help the fuel feed t= o=20 the engine. Sort of makes sense to me. I have no idea if it works at all= .=20 I've never found a bug in a vent line, but the vent lines are definitely= =20 part of my preflight inspection. I would guess that vent lines don't get= =20 clogged during flight (maybe ice?). They only get foreign matter in the= =20 inlet on the ground. =20 I can only think of two times that you need to have air flowing out of a = =20 fuel tank. One is when ambient temperatures rise and the air expands in the= =20 tank. The other is during a climb when you're feeding off the other tank.= =20 Fuel also expands with heat, but not nearly as much as air. We've all had= =20 fuel spill out a vent from heat expansion when we've topped of our tanks= =20 and left the plane on the ramp. None of these is a particularly high flow= =20 rate so the two small holes in the Andair check valve should be able to =20 handle that amount of back flow. =20 My bigger concern is how much the Andair valve restricts the air flow into = =20 the tank when you're using fuel from that tank. Andair lists a "cracking = =20 pressure" of 0.4 to 0.7 psi. I'm not capable or qualified to analyze how = =20 much that would effect fuel flow in a low wing aircraft. But the differen= ce=20 between a small NACA scoop slightly pressurizing the tank and a check=20 valve that creates a slightly negative pressure in the fuel tank might be = =20 enough for me to leave check valves off my plane. The number of installed= check=20 valves probably proves this isn't really an issue, however. =20 You can't inspect them during a preflight either. =20 You might be able to make the argument that check valves ad a potential =20 failure point that only eliminates a slight inconvenience of a little fuel = =20 spilling out while taxiing. =20 Mike Easley Colorado Springs =20 =20 In a message dated 5/19/2011 2:45:52 P.M. Mountain Daylight Time, =20 colyncase@earthlink.net writes: That would be 1.4 miles per hour. Wonder what a naca vent that gets the= =20 air to slow down smoothly from 250 mph down to 1.4 looks like? =20 On May 19, 2011, at 11:11 AM, _MikeEasley@aol.com_=20 (mailto:MikeEasley@aol.com) wrote: I had to drain a tank on a IV to repair a fuel leak. I plugged the vent= =20 while I removed the drain valve from the bottom of the wing, with the hope= =20 that it would slow the flow of fuel down my arm. I only got about a half= =20 gallon from the tank until the flow slowed to a drip. I don't think the= =20 engine driven pump or boost pump could overcome the vacuum caused by a clo= gged=20 vent line. So a clogged vent would stop the engine I'm guessing, not caus= e=20 it to surge. =20 I did the calculation one time to determine the air flow that has to come= =20 in the vents to replace the fuel going into the engine. I have 3/8" vent= =20 lines on my ES and that air is moving through that vent line a couple feet= =20 per second if I remember correctly. =20 Mike Easley Colorado Springs =20 =20 In a message dated 5/18/2011 6:42:57 A.M. Mountain Daylight Time,=20 _n5zq@verizon.net_ (mailto:n5zq@verizon.net) writes: =20 Good point, Bill. The check valves supplied by Lancair for the vent system= =20 on my IV are free flowing inward and =E2=80=9Csomewhat=E2=80=9D restricted = flowing =20 outward. This prevents venting a lot of fuel overboard while taxiing with = full=20 wing tanks (no winglets) yet allows air to escape at a relatively slow rat= e=20 to avoid the problem that you describe. Certainly, a normal one way valve= =20 (free flow one direction =E2=80=93 no flow in the other) should NOT be use= d on a vent=20 system. =20 Bill Harrelson N5ZQ 320 1,900 hrs N6ZQ IV under construction =20 =20 =20 =20 =20 =20 From: _Bill Hannahan_ (mailto:wfhannahan@yahoo.com) =20 Sent: Wednesday, May 18, 2011 7:43 AM To: _lml@lancaironline.net_ (mailto:lml@lancaironline.net) =20 Subject: [LML] Fuel restriction or air? =20 _ =20 {Did you verify the fuel vents are working properly? ....and that the=20 check valves on the vents are oriented correctly?}=20 There should be no check valves on vent lines. If you take off at sea=20 level with a wing tank at atmospheric pressure, 14.7 psia trapped by a che= ck=20 valve, and climb to 18,000 feet, static pressure 7.35 psia, the differenti= al=20 pressure on the tank will be 7.35 psi, 1,058 pounds per square foot trying= =20 to rip the skins off the spar and ribs.=20 Vent lines must be free flowing both directions.=20 Regards, Bill Hannahan wfhannahan@yahoo.com_ (mailto:wfhannahan@yahoo.com)=20 =3D --part1_36827.7f93daf2.3b07c6bf_boundary Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en
Colyn,
 
The ES has tiny NACA scoops in the wingtips like the IV with the= =20 thought that they would slightly pressurize the fuel tanks to help the fuel= feed=20 to the engine.  Sort of makes sense to me.  I have no idea if it = works=20 at all.  I've never found a bug in a vent line, but the vent line= s are=20 definitely part of my preflight inspection.  I would guess that vent l= ines=20 don't get clogged during flight (maybe ice?).  They only get foreign m= atter=20 in the inlet on the ground.
 
I can only think of two times that you need to have air flowing out of= a=20 fuel tank. One is when ambient temperatures rise and the air expands i= n the=20 tank.  The other is during a climb when you're feeding off the ot= her=20 tank.  Fuel also expands with heat, but not nearly as much as air.&nbs= p;=20 We've all had fuel spill out a vent from heat expansion when we've topped o= f our=20 tanks and left the plane on the ramp.  None of these is a particularly= high=20 flow rate so the two small holes in the Andair check valve should be able t= o=20 handle that amount of back flow.
 
My bigger concern is how much the Andair valve restricts the air flow = into=20 the tank when you're using fuel from that tank.  Andair lists a "crack= ing=20 pressure" of 0.4 to 0.7 psi.  I'm not capable or qualified to analyze = how=20 much that would effect fuel flow in a low wing aircraft.  But the=20 difference between a small NACA scoop slightly pressurizing the tank a= nd a=20 check valve that creates a slightly negative pressure in the fuel tank migh= t be=20 enough for me to leave check valves off my plane.  The= =20 number of installed check valves probably proves this isn't really an issue= ,=20 however.
 
You can't inspect them during a preflight either.
 
You might be able to make the argument that check valves ad a potentia= l=20 failure point that only eliminates a slight inconvenience of a little fuel= =20 spilling out while taxiing.
 
Mike Easley
Colorado Springs
 
In a message dated 5/19/2011 2:45:52 P.M. Mountain Daylight Time,=20 colyncase@earthlink.net writes:
= That=20 would be 1.4 miles per hour.   Wonder what a naca vent that gets the= air=20 to slow down smoothly  from 250 mph down to 1.4 looks like?=20

On May 19, 2011, at 11:11 AM, MikeEasley@aol.com wrote:
<= FONT=20 color=3D#000000 size=3D2 face=3DArial>
I had to drain a tank on a IV to repair a fuel leak.  I plugg= ed=20 the vent while I removed the drain valve from the bottom of the wing, w= ith=20 the hope that it would slow the flow of fuel down my arm.  I only = got=20 about a half gallon from the tank until the flow slowed to a drip. = ; I=20 don't think the engine driven pump or boost pump could overcome the vac= uum=20 caused by a clogged vent line.  So a clogged vent would stop the e= ngine=20 I'm guessing, not cause it to surge.
 
I did the calculation one time to determine the air flow that has = to=20 come in the vents to replace the fuel going into the engine.  I ha= ve=20 3/8" vent lines on my ES and that air is moving through that vent = line=20 a couple feet per second if I remember correctly.
 
Mike Easley
Colorado Springs
 
In a message dated 5/18/2011 6:42:57 A.M. Mountain Daylight Time, = n5zq@verizon.net writes:
Good point, Bill. The check valves supplied by Lancair for the v= ent=20 system on my IV are free flowing inward and =E2=80=9Csomewhat=E2=80= =9D restricted flowing=20 outward. This prevents venting a lot of fuel overboard while taxiing = with=20 full wing tanks (no winglets) yet allows air to escape at a relativel= y=20 slow rate to avoid the problem that you describe. Certainly, a normal= one=20 way valve (free flow one direction =E2=80=93 no flow in the other) sh= ould NOT be=20 used on a vent system.
 
Bill Harrelson
N5ZQ 320 1,900 hrs
N6ZQ  IV under construction
 
 
 
 
From: Bill=20 Hannahan
Sent: Wednesday, May 18, 2011 7:43 AM
To: lml@lancaironline.net
Subject: [LML] Fuel restriction or air?
 

 

{Did you verify the fuel vents are working= =20 properly?   ....and that the check valves on the vent= s are=20 oriented correctly?}

 

There should be no check valves on vent li= nes. If=20 you take off at sea level with a wing tank at atmospheric press= ure,=20 14.7 psia trapped by a check valve, and climb to 18,000 feet, s= tatic=20 pressure 7.35 psia, the differential pressure on the tank will = be=20 7.35 psi, 1,058 pounds per square foot trying to rip the skins = off=20 the spar and ribs.

 

Vent lines must be free flowing both=20 directions.


 

Regards,
Bill Hannahan


=3D --part1_36827.7f93daf2.3b07c6bf_boundary--