X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 01 Dec 2008 18:21:05 -0500 Message-ID: X-Original-Return-Path: Received: from web33905.mail.mud.yahoo.com ([209.191.69.183] verified) by logan.com (CommuniGate Pro SMTP 5.2.10) with SMTP id 3323897 for lml@lancaironline.net; Sun, 30 Nov 2008 12:53:53 -0500 Received: (qmail 10428 invoked by uid 60001); 30 Nov 2008 17:53:54 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:X-Mailer:Date:From:Reply-To:Subject:To:In-Reply-To:MIME-Version:Content-Type:Message-ID; b=ZUDg/uVXVlR9yvEy/WVJK0O/od6V0yOvOrfv/5CtJWYzKNZeCyN/8dVWxd0lMBwjFH1ajMFoPhRhpk+Geg4gZ4+1K/qoaW/nuBU0rBNv4gaN2lfOcBIbu2KKzKBoyU6W09tKL2+9/qOLT7fQWDMbSv4tmfp3mO1BJesZUUB8U1U=; X-YMail-OSG: f6hSNF8VM1mhW8Qm.0nu_2.UsF.9u3jptqx_is2pvpUkx_y0FgG8uyN5v7LQs1qEUfXebO7q_0J9.f7w4SelBVmhNWiqt9IA.Apwp81pzZit0ZMXcswxGa4ZRczblUigkdt1z5nwvS9H1SXJvTNN_LXH27KVNBAhToyIWAYtObxBcQ-- Received: from [71.210.211.138] by web33905.mail.mud.yahoo.com via HTTP; Sun, 30 Nov 2008 09:53:54 PST X-Mailer: YahooMailWebService/0.7.260.1 X-Original-Date: Sun, 30 Nov 2008 09:53:54 -0800 (PST) From: Bill Hannahan Reply-To: wfhannahan@yahoo.com Subject: Re: [LML] Tank vent. X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-1151950458-1228067634=:9382" X-Original-Message-ID: <290744.9382.qm@web33905.mail.mud.yahoo.com> --0-1151950458-1228067634=:9382 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable =A0 Regarding this comment; =A0 =93You guys are too well educated with all your calculations.=A0You are confusing yourselves and each other.=A0Look at other aircraft in the hangar, they all work well some have 3/8"=A0 and some 1/4".=85=A0 Stop your intellectual aerobatics and get on withthe job.=94 =A0 =A0 The Boeing 747 racked up a lot of hours before a center fuel tank on one blew up. Did those hours prove that the fuel system was risk fr= ee? No. =A0 The Concord only had one accident, but the Concord accident RATE, accidents per billion miles, was much worse than for the 747. Did the accident free hours prove that the Concord could survive a tire failure? No. =A0 Lancairs have a much higher accident rate than the Concord. Do those accidents prove that all engineering risk factors have been identi= fied and eliminated? No.=20 =A0 In the course of blogging for a rational energy policy I have received countless disparaging remarks over the years. I understand th= at they are a reflection on their author. Many Lancair builders are thoughtful= intelligent people with good ideas, but some are more sensitive and choose not to participate to avoid deprecating responses. =A0 The problem is that their missing input makes my life and your life more dangerous than they need to be. So if you find yourself writ= ing a flaming comment, save yourself some embarrassment and do us all a favor b= y not clicking the send button. =A0 We have not talked much about fuel tank vent systems, but our lives depend on them. They deserve a full analysis that includes all possible conditions, not just straight and level.=20 =A0 In a worst case emergency like fire in the cockpit, I would lower the gear and descend at near red line speed. I expect a sink rate in = the range of 6,000 =96 10,000 fpm. If a wing tank is empty I would expect to se= e it being crushed in the lower altitudes. No good choices there. =A0 How many Lancairs have made an emergency maximum rate descent from high altitude to sea level with an empty wing tank, any volunteers? =A0 =93I was thinking about putting 3/8 vent line in my header tank (under construct= ion) but the opposite question is --- would it over pressure the tank?=94 =A0 Under steady state conditions the pressure depends largely on the angle of the vent opening with respect to the wind as explained by C= hris Zavatson.=20 =A0 =93The vent can=A0act much like a pitot tube and easily capture most if not all of the available ram pressure.=A0 Our wings show visible deformation, even under just one psi.=A0 Lung pressure is enough to see it.=A0 =85.=A0 In flight I could see the ribs as my skins were bulging = under pressure.=A0 Attaching an airspeed indicator to the vent line indicated almost full ram pressure.=A0 I began filing the underside until pressure drop to just a few tenths of a psi.=94 =A0 Like Chris, I reduced the angle on my vents to=A0 about 10 deg to avoid exc= essive tank pressure.=20 =A0 At 300 mph CAS, the dynamic pressure is 60.9 inches of water, 30 psi, 4,305 pounds per square foot. We do not want that kind of pressure trying to blow the skins off our wings. I do not know how efficien= t the NACA vents on LIV wing tip vents are at converting airspeed to pressure= . It is probably highly dependent on the exact location and orientation of the v= ent. I would like to see some data on that. =A0 =93Any hole in your airplane should be as small as possible in order to get it's job done.=94 =A0 Not true. The smallest possible hole is no hole at all. Each hole has an optimum size based on its function and environment. =A0 Bill Hannahan =20 wfhannahan@yahoo.com --- On Fri, 11/28/08, Ian Crowe wrote: From: Ian Crowe Subject: [LML] Tank vent. To: lml@lancaironline.net Date: Friday, November 28, 2008, 1:25 PM =20 =20 You guys are too well educated with all your=20 calculations.=A0You are confusing yourselves and each other.=A0Look at=20 other aircraft in the hangar, they all work well some have 3/8"=A0 and some= =20 1/4". Some face forward others are=A0just proud of the wing and have a=20 45degree chamfer. =A0 I have a Lancair 360 with the extended fuel tanks=20 and the 3/8" vent goes from the outboard tank to atmosphere.=A0 Never a=20 problem, fuel flows keep the engine purring and the wings show no signs of= =20 collapse!!!!! =A0 Stop your intellectual aerobatics and get on=20 withthe job. =A0 Happy Thanksgiving from a Canadian=20 cousin. =A0 Ian B.=A0 Crowe LNC 2=20 C-FKRO=0A=0A=0A --0-1151950458-1228067634=:9382 Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable


 

Regarding this comment;

 

=93You guys are too well educated with all your calculations. You are confusing yourselves and each other. Look a= t other aircraft in the hangar, they all work well some have 3/8"  and some 1/4".=85  Stop your intellectual aerobatics and get on withthe job.=94

 

 

The Boeing 747 racked up a lot of hours before a cen= ter fuel tank on one blew up. Did those hours prove that the fuel system was risk fr= ee? No.

 

The Concord only had one accident, but the Concord accident RATE, accidents per billion miles, was much worse than for the 747. Did the accident free hours prove that the Concord= could survive a tire failure? No.

 

Lancairs have a much higher accident rate than the <= st1:City>Concord. Do those accidents prove that all engineering risk factors have been identi= fied and eliminated? No.

 

In the course of blogging for a rational energy poli= cy I have received countless disparaging remarks over the years. I understand th= at they are a reflection on their author. Many Lancair builders are thoughtful= intelligent people with good ideas, but some are more sensitive and choose not to participate to avoid deprecating responses.

 

The problem is that their missing input makes my lif= e and your life more dangerous than they need to be. So if you find yourself writ= ing a flaming comment, save yourself some embarrassment and do us all a favor b= y not clicking the send button.

 

We have not talked much about fuel tank vent systems= , but our lives depend on them. They deserve a full analysis that includes all possible conditions, not just straight and level.

 

In a worst case emergency like fire in the cockpit, = I would lower the gear and descend at near red line speed. I expect a sink rate in = the range of 6,000 =96 10,000 fpm. If a wing tank is empty I would expect to se= e it being crushed in the lower altitudes. No good choices there.

 

How many Lancairs have made an emergency maximum rat= e descent from high altitude to sea level with an empty wing tank, any volunteers?

 

=93I was thinking about putting 3/8 vent line in my header tank (under construct= ion) but the opposite question is --- would it over pressure the tank?=94

 

Under steady state conditions the pressure depends l= argely on the angle of the vent opening with respect to the wind as explained by <= span class=3D"email">Chris Zavatson.

 

=93The vent can act much like a pitot tube and = easily capture most if not all of the available ram pressure.  Our wings show visible deformation, even under just one psi.  Lung pressure is enough= to see it.  =85.  In flight I could see the ribs as my skins were bu= lging under pressure.  Attaching an airspeed indicator to the vent line indicated almost full ram pressure.  I began filing the underside until pressure drop to just a few tenths of a psi.=94

 

Like Chris, I reduced the angle on my vents to  about 10 deg to avoid excessive tank pressure.

 

At 300 mph CAS, the dynamic pressure is 60.9 inches = of water, 30 psi, 4,305 pounds per square foot. We do not want that kind of pressure trying to blow the skins off our wings. I do not know how efficien= t the NACA vents on LIV wing tip vents are at converting airspeed to pressure= . It is probably highly dependent on the exact location and orientation of the v= ent. I would like to see some data on that.

 

=93Any hole in your airplane should be as small as p= ossible in order to get it's job done.=94

 

Not true. The smallest possible hole is no hole at a= ll. Each hole has an optimum size based on its function and environment.

 

Bill Hannahan

--- On Fri, 11/28/08, Ian Crowe <ian.crowe@sympatico.ca><= /i> wrote:
From: Ian Crowe <ian.crowe@sy= mpatico.ca>
Subject: [LML] Tank vent.
To: lml@lancaironline.netDate: Friday, November 28, 2008, 1:25 PM

=20 =20
You guys are too well educated with al= l your=20 calculations. You are confusing yourselves and each other. Look a= t=20 other aircraft in the hangar, they all work well some have 3/8"  and s= ome=20 1/4". Some face forward others are just proud of the wing and have a= =20 45degree chamfer.
 
I have a Lancair 360 with the extended= fuel tanks=20 and the 3/8" vent goes from the outboard tank to atmosphere.  Never a= =20 problem, fuel flows keep the engine purring and the wings show no signs of= =20 collapse!!!!!
 
Stop your intellectual aerobatics and = get on=20 withthe job.
 
Happy Thanksgiving from a Canadian=20 cousin.
 
Ian B.  Crowe
LNC 2=20 C-FKRO

=0A=0A=0A=0A = --0-1151950458-1228067634=:9382--