X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 24 May 2011 13:23:22 -0400 Message-ID: X-Original-Return-Path: Received: from elasmtp-dupuy.atl.sa.earthlink.net ([209.86.89.62] verified) by logan.com (CommuniGate Pro SMTP 5.4c3j) with ESMTP id 4991877 for lml@lancaironline.net; Mon, 23 May 2011 12:33:36 -0400 Received-SPF: none receiver=logan.com; client-ip=209.86.89.62; envelope-from=colyncase@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=belEqoOdAwps6oyb8zga2weC1won6djgUamF4KnZDvwlm47xi+guzPknPl1be2Of; h=Received:From:Mime-Version:Content-Type:Subject:Date:In-Reply-To:To:References:Message-Id:X-Mailer:X-ELNK-Trace:X-Originating-IP; Received: from [216.57.118.194] (helo=[192.168.1.131]) by elasmtp-dupuy.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1QOY3z-0000dA-A3 for lml@lancaironline.net; Mon, 23 May 2011 12:33:03 -0400 From: Colyn Case Mime-Version: 1.0 (Apple Message framework v1082) Content-Type: multipart/alternative; boundary=Apple-Mail-421--703815338 Subject: Re: [LML] Re: Fuel restriction or air, Fuel Vent Check Valves X-Original-Date: Mon, 23 May 2011 12:33:02 -0400 In-Reply-To: X-Original-To: "Lancair Mailing List" References: X-Original-Message-Id: X-Mailer: Apple Mail (2.1082) X-ELNK-Trace: 63d5d3452847f8b1d6dd28457998182d7e972de0d01da940876147ffd6e73d9e5ee6754668bd7fad350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 216.57.118.194 --Apple-Mail-421--703815338 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 good points. My wonder was whether the naca vent is way bigger than it needs to be. =20= The complication point is well taken.=20 I guess my problem is the memory of a IV dumping a couple gallons on the = pavement once. Colyn On May 23, 2011, at 8:03 AM, MikeEasley@aol.com wrote: > Colyn, > =20 > The ES has tiny NACA scoops in the wingtips like the IV with the = thought that they would slightly pressurize the fuel tanks to help the = fuel feed to the engine. Sort of makes sense to me. I have no idea if = it works at all. I've never found a bug in a vent line, but the vent = lines are definitely part of my preflight inspection. I would guess = that vent lines don't get clogged during flight (maybe ice?). They only = get foreign matter in the inlet on the ground. > =20 > I can only think of two times that you need to have air flowing out of = a fuel tank. One is when ambient temperatures rise and the air expands = in the tank. The other is during a climb when you're feeding off the = other tank. Fuel also expands with heat, but not nearly as much as air. = We've all had fuel spill out a vent from heat expansion when we've = topped of our tanks and left the plane on the ramp. None of these is a = particularly high flow rate so the two small holes in the Andair check = valve should be able to handle that amount of back flow. > =20 > My bigger concern is how much the Andair valve restricts the air flow = into the tank when you're using fuel from that tank. Andair lists a = "cracking pressure" of 0.4 to 0.7 psi. I'm not capable or qualified to = analyze how much that would effect fuel flow in a low wing aircraft. = But the difference between a small NACA scoop slightly pressurizing the = tank and a check valve that creates a slightly negative pressure in the = fuel tank might be enough for me to leave check valves off my plane. = The number of installed check 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 failure point that only eliminates a slight inconvenience of a = little fuel spilling out while taxiing. > =20 > Mike Easley > Colorado Springs > =20 > In a message dated 5/19/2011 2:45:52 P.M. Mountain Daylight Time, = colyncase@earthlink.net writes: > That would be 1.4 miles per hour. Wonder what a naca vent that gets = the 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 wrote: >=20 >> I had to drain a tank on a IV to repair a fuel leak. I plugged the = vent while I removed the drain valve from the bottom of the wing, with = the hope that it would slow the flow of fuel down my arm. I only got = about a half gallon from the tank until the flow slowed to a drip. I = don't think the engine driven pump or boost pump could overcome the = vacuum caused by a clogged vent line. So a clogged vent would stop the = engine I'm guessing, not cause it to surge. >> =20 >> I did the calculation one time to determine the air flow that has to = come in the vents to replace the fuel going into the engine. I have = 3/8" vent lines on my ES and that air is moving through that vent line a = couple feet per second if I remember correctly. >> =20 >> Mike Easley >> Colorado Springs >> =20 >> 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 vent = system on my IV are free flowing inward and =93somewhat=94 restricted = flowing outward. This prevents venting a lot of fuel overboard while = taxiing with full wing tanks (no winglets) yet allows air to escape at a = relatively slow rate to avoid the problem that you describe. Certainly, = a normal one way valve (free flow one direction =96 no flow in the = other) should NOT be used on a vent system. >> =20 >> Bill Harrelson >> N5ZQ 320 1,900 hrs >> N6ZQ IV under construction >> =20 >> =20 >> =20 >> =20 >> From: Bill Hannahan >> Sent: Wednesday, May 18, 2011 7:43 AM >> To: lml@lancaironline.net >> Subject: [LML] Fuel restriction or air? >> =20 >> =20 >> {Did you verify the fuel vents are working properly? ....and that = the check valves on the vents are oriented correctly?} >> =20 >> There should be no check valves on vent lines. If you take off at sea = level with a wing tank at atmospheric pressure, 14.7 psia trapped by a = check valve, and climb to 18,000 feet, static pressure 7.35 psia, the = differential pressure on the tank will be 7.35 psi, 1,058 pounds per = square foot trying to rip the skins off the spar and ribs. >> =20 >> Vent lines must be free flowing both directions. >>=20 >> =20 >> Regards, >> Bill Hannahan >>=20 >> wfhannahan@yahoo.com >>=20 >=20 > =3D --Apple-Mail-421--703815338 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252 good = points.
My wonder was whether the naca vent is way bigger than it = needs to be.   

The complication = point is well taken. 
I guess my problem is the memory of = a IV dumping a couple gallons on the pavement = once.

Colyn

On May 23, = 2011, at 8:03 AM, MikeEasley@aol.com = wrote:

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 = lines are=20 definitely part of my preflight inspection.  I would guess that = vent lines=20 don't get clogged during flight (maybe ice?).  They only get = foreign matter=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 in the=20 tank.  The other is during a climb when you're feeding off the = other=20 tank.  Fuel also expands with heat, but not nearly as much as = air. =20 We've all had fuel spill out a vent from heat expansion when we've = topped of 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 to=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 = "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=20= difference between a small NACA scoop slightly pressurizing the = tank and a=20 check 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=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 = potential=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:

I had to drain a tank on a IV to repair a fuel leak.  I = plugged=20 the vent while I removed the drain valve from the bottom of the = wing, with=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 = vacuum=20 caused by a clogged vent line.  So a clogged vent would stop = the engine=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 = have=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 vent=20 system on my IV are free flowing inward and =93somewhat=94 = 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 = relatively=20 slow rate to avoid the problem that you describe. Certainly, a = normal one=20 way valve (free flow one direction =96 no flow in the other) = should NOT be=20 used on a vent system.
 
Bill Harrelson
N5ZQ 320 1,900 hrs
N6ZQ  IV under construction
 
 
 
 
Sent: Wednesday, May 18, 2011 7:43 AM
Subject: [LML] Fuel restriction or = air?
 

=3D
= --Apple-Mail-421--703815338--

 

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

 

There = should be no check valves on vent lines. If=20 you take off at sea level with a wing tank at atmospheric = pressure,=20 14.7 psia trapped by a check valve, and climb to 18,000 = feet, static=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