X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 19 May 2011 11:11:52 -0400 Message-ID: X-Original-Return-Path: Received: from elasmtp-kukur.atl.sa.earthlink.net ([209.86.89.65] verified) by logan.com (CommuniGate Pro SMTP 5.4c3j) with ESMTP id 4988520 for lml@lancaironline.net; Thu, 19 May 2011 09:15:37 -0400 Received-SPF: none receiver=logan.com; client-ip=209.86.89.65; envelope-from=colyncase@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=LzTF4eenh+iDq9qM8qWAwhhb6ae3L8cK2UQ83CglrPI4gvqskBrng/liOJzIT2f6; 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-kukur.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1QN348-00054S-WB for lml@lancaironline.net; Thu, 19 May 2011 09:15:01 -0400 From: Colyn Case Mime-Version: 1.0 (Apple Message framework v1082) Content-Type: multipart/alternative; boundary=Apple-Mail-269--1061298178 Subject: Re: [LML] Re: Fuel restriction or air? X-Original-Date: Thu, 19 May 2011 09:14:59 -0400 In-Reply-To: X-Original-To: "Lancair Mailing List" References: X-Original-Message-Id: <6DF53FAC-52DD-4C8D-A440-F339FAEB69F1@earthlink.net> X-Mailer: Apple Mail (2.1082) X-ELNK-Trace: 63d5d3452847f8b1d6dd28457998182d7e972de0d01da9409693ed5cf307c9712a0428b678662275350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 216.57.118.194 --Apple-Mail-269--1061298178 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 Bill, I happen to be putting these valves in now. I talked to the lady at = Andair and got an answer that approximates what you have below. ....However, it would be comforting to have some actual data. Did you = happen to do any testing? e.g. in a 2000 fpm climb you need to lose about 1.5" of mercury per = minute to avoid pressurizing. The worst case would be nearly empty = tanks because more volume of air would have to escape to maintain nearly = neutral pressure. On May 18, 2011, at 8:42 AM, Bill Harrelson wrote: > 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 --Apple-Mail-269--1061298178 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252


On May 18, 2011, at = 8:42 AM, Bill Harrelson wrote:

Good point, Bill. The check valves supplied by Lancair for the vent = system=20 on my IV are free flowing inward and =93somewhat=94 restricted flowing = outward. This=20 prevents venting a lot of fuel overboard while taxiing with full wing = tanks (no=20 winglets) yet allows air to escape at a relatively slow rate to avoid = the=20 problem that you describe. Certainly, a normal one way valve (free flow = one=20 direction =96 no flow in the other) should NOT be 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?
 

= --Apple-Mail-269--1061298178--
=20 =20

 

{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 you=20 take off at sea level with a wing tank at atmospheric pressure, = 14.7 psia=20 trapped by a check valve, and climb to 18,000 feet, static = pressure 7.35=20 psia, the differential pressure on the tank will be 7.35 psi, = 1,058 pounds=20 per square foot trying to rip the skins off the spar and = ribs.

 

Vent lines must be free flowing both=20 directions.


 

Regards,
Bill Hannahan