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 nm10-vm0.bullet.mail.ne1.yahoo.com ([98.138.91.72] verified) by logan.com (CommuniGate Pro SMTP 5.4c3j) with SMTP id 4992225 for lml@lancaironline.net; Mon, 23 May 2011 18:05:07 -0400 Received-SPF: none receiver=logan.com; client-ip=98.138.91.72; envelope-from=wfhannahan@yahoo.com Received: from [98.138.90.55] by nm10.bullet.mail.ne1.yahoo.com with NNFMP; 23 May 2011 22:04:32 -0000 Received: from [98.138.87.6] by tm8.bullet.mail.ne1.yahoo.com with NNFMP; 23 May 2011 22:04:32 -0000 Received: from [127.0.0.1] by omp1006.mail.ne1.yahoo.com with NNFMP; 23 May 2011 22:04:32 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 275887.62568.bm@omp1006.mail.ne1.yahoo.com Received: (qmail 99033 invoked by uid 60001); 23 May 2011 22:04:31 -0000 DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:MIME-Version:Content-Type; b=hs1Rn1PAKdSTo4aFLXg/kQedz/Zd3QwoMR0co2EbzK3EQ9y0Ez2y6aS021ksln5tIw223/F93DfRWEcyrX2weEUaiTURlPik1l/c4ie916aW5AoEipPo1vsXQjprW71THZJs1QGyoJLRr8VXfwzRrqJS5IrYM4LrU3rT1+02KKQ=; X-Original-Message-ID: <753711.91215.qm@web33904.mail.mud.yahoo.com> X-YMail-OSG: g8WWKH4VM1lAGr7ooniORbe654wtn.v9Ce1e.36tzEmcuqc lYHbkZ8vJ1SnTfz3pGKmEjAVVXzikTcblXIglgvuVhR1v6IhzUwekMwu2u_e oFYmzHQtdCcfgqVUPZ4.PHcO.FXgTMENYZOycJKVGgEOVNA5RxcfRl_TO7A3 GgRWnQfb.nlIeUW2ez5m7WGYiOzHrCW..q4MVFmtM27hJAR3c897fpU7cFXu qzGVWSOhkON5x2MQGVzY6yq_QQez1PlTOwIMOxIS_q4DmmZeTsf33oSGaBNM mHpZas3nDOW7vsAoH7xFxmPU8NsyHH20AVACJh9h7mZgqhzwDtfQK2AzDkrw MfponI6wtIg77wn2ZZAdOzKNIxnvHK8x9S8RG0oKEp7usvYF18EQPVfx4AUm roQbudRJSzKEHPmcQjIbfXC.brttN62Hkv5lwVWA_LaI4Mv4gEBgnRIU8xKX ERAuwNRPeQIvq Received: from [174.29.152.94] by web33904.mail.mud.yahoo.com via HTTP; Mon, 23 May 2011 15:04:31 PDT X-Mailer: YahooMailClassic/14.0.1 YahooMailWebService/0.8.111.303096 X-Original-Date: Mon, 23 May 2011 15:04:31 -0700 (PDT) From: Bill Hannahan Subject: Fuel restriction or air, Fuel Vent Check Valves X-Original-To: MAIL LANCAIR MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-899988205-1306188271=:91215" --0-899988205-1306188271=:91215 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable =0A=0A=0A=0A =0ARegarding this;=20 =0A =0A{ the Andair check valves (at least the model I got) are marked 1psi req= uired=0Ato push air out the valve. =0A=0ASo each wing would have about 50 s= quare feet top and bottom=0Aor about 100 lbs. total force trying to blow th= e wing apart.} =0A =0A =0AThere are 144 square inches in one square foot. 1 psi is equivalent to 1= 44=0Apounds per square foot. The 320/360 with extended fuel tanks has about= 15=0Asquare feet of wing tank, so about 2,200 pounds of force on each skin= at 1 psi.=0A=0A=C2=A0=0A=0A=C2=A0=0A=0ARegarding this;=0A=0A=C2=A0=0A=0A{ = The ES has tiny NACA scoops in the wingtips like the IV=0Awith the thought = that they would slightly pressurize the fuel tanks to help the=0Afuel feed = to the engine.=C2=A0 Sort of makes=0Asense to me.=C2=A0 I have no idea if i= t works=0Aat all.}=0A=0A=C2=A0=0A=0AThe pressure produced by a NACA scoop i= s not proportional to=0Aits size. A poorly designed or poorly located scoop= may produce no pressure=0Again at all. A well designed NACA scoop located = near the front of a body, that=0Ais, where the shape is still expanding, su= ch that you can see the inlet standing=0Adirectly in front of it, may well = produce full dynamic pressure at zero flow,=0Alike a pitot tube.=0A=0A=C2= =A0=0A=0AOut of curiosity, I have looked at many fuel vents at=0Afly-ins. T= here is great variation in type and location. Some are located such=0Athat = I would expect them to produce near full dynamic pressure.=0A=0A=C2=A0=0A= =0ADynamic pressure increases with the square of velocity. At=0A200 knots C= AS it is 27 inches of water, about 1 psi. 300 knots equals 62 inches=0Aof w= ater, 2.2 psi, 317 pounds per square foot trying to blow the skins off the= =0Awing.=0A=0A=C2=A0=0A=0Ahttp://www.iflyez.com/manometer.shtml=0A=0A=C2=A0= =0A=0ARegarding this;=0A=0A=C2=A0=0A=0A{Having a check valve or float valve= in the vent line is=0Acommon in certified aircraft so I disagree that vent= lines must be free flowing=0Ain both directions.=C2=A0 The twin cessnas us= e=0Aa float system to block the vent when fuel is present. This has led to = problems=0Awith unanticipated blockage of the vent line leading to ADs like= this one:}=0A=0A=C2=A0=0A=0AI think the AD makes a good case for free flow= ing vent=0Alines.=0A=0A=C2=A0=0A=0AImagine you have a vent with a float val= ve. You have an=0Aearly morning departure from Phoenix=0Aand top the tanks = the night before. Something comes up that delays the trip one=0Aday and you= r plane sits on the ramp where temperatures skyrocket during the day.=0AThe= fuel expands, the float valve closes, and the wing is structurally damaged= =0Aby expanding fuel. The damage may be indicated by a big fuel stain on th= e ramp,=0Athen again it may not be indicated until you take off.=0A=0A=C2= =A0=0A=0AI am somewhat suspect of multiple vents to one tank. I met a=0Abui= lder with a BD4. He had doubts about the wing tip vents, so he had drilled= =0Anumerous holes in his inboard mounted fuel caps. I pointed out that with= =0Agasoline, the fuel vapor concentration is usually above the combustion l= imit,=0Abut with the fuel cap in a low pressure region, and the tip vent ge= tting ram=0Aair, there would be a continuous flow of fresh air through his = tank that could=0Amake it combustible. A static spark near the vent could s= et it off. He thought=0Athat was interesting.=0A=0A=C2=A0=0A=0AA check valv= e in the cap allowing air in, not out is probably OK=0Aas long as the main = vent is not in a negative pressure region, but it might allow=0Awater in wh= ile sitting on the ramp.=0A=0A=C2=A0=0A=0AI=E2=80=99m a big fan of the Keep= It Simple principle regarding=0Afuel vents. I only top off a few times a y= ear for long trips and regard the=0Apossibility of a little spillage taxiin= g out as a small price to pay.=0A=0A=C2=A0=0A=0A=C2=A0=0A=0ARegards, Bill = Hannahan =20 wfhannahan@yahoo.com --0-899988205-1306188271=:91215 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable

= =0A=0A=0A


=0ARegarding this;
=0A<= br>=0A{ the Andair check valves (at least the model I got) are marked 1psi = required=0Ato push air out the valve.

=0A=0A

So e= ach wing would have about 50 square feet top and bottom=0Aor about 100 lbs.= total force trying to blow the wing apart.}
=0A
=0A
=0AThere are = 144 square inches in one square foot. 1 psi is equivalent to 144=0Apounds p= er square foot. The 320/360 with extended fuel tanks has about 15=0Asquare = feet of wing tank, so about 2,200 pounds of force on each skin at 1 psi.=0A=0A

 

=0A=0A

 

=0A=0A

Regarding this;

= =0A=0A

 

=0A=0A

{ The ES has tiny NACA scoops in the wingtips like the IV=0Awith the th= ought that they would slightly pressurize the fuel tanks to help the=0Afuel= feed to the engine.  Sort of makes=0Asense to= me.  I have no idea if it works=0Aat all.}=0A=0A

 

=0A=0A

The pressure produced by a NACA scoop is not proportional to=0Aits siz= e. A poorly designed or poorly located scoop may produce no pressure=0Again= at all. A well designed NACA scoop located near the front of a body, that= =0Ais, where the shape is still expanding, such that you can see the inlet = standing=0Adirectly in front of it, may well produce full dynamic pressure = at zero flow,=0Alike a pitot tube.

=0A=0A

&nb= sp;

=0A=0A

Out of curiosity, I have looked a= t many fuel vents at=0Afly-ins. There is great variation in type and locati= on. Some are located such=0Athat I would expect them to produce near full d= ynamic pressure.

=0A=0A

 

=0A=0A

Dynamic pressure increases with the squa= re of velocity. At=0A200 knots CAS it is 27 inches of water, about 1 psi. 3= 00 knots equals 62 inches=0Aof water, 2.2 psi, 317 pounds per square foot t= rying to blow the skins off the=0Awing.

=0A=0A

 

=0A=0A

http://www.iflyez.com/manometer.shtml

=0A=0A 

=0A=0A

Rega= rding this;

=0A=0A

 

=0A=0A

{Having a check valve or float valve in the vent line is= =0Acommon in certified aircraft so I disagree that vent lines must be free = flowing=0Ain both directions.  The twin cessna= s use=0Aa float system to block the vent when fuel is present. This has led= to problems=0Awith unanticipated blockage of the vent line leading to ADs = like this one:}

=0A=0A

 

=0A=0A=

I think the AD makes a good case for free flowing ve= nt=0Alines.

=0A=0A

 

=0A=0A

Imagine you have a vent with a float valve. You have an= =0Aearly morning departure from Phoenix=0Aand top the tanks the night before. Something comes up that dela= ys the trip one=0Aday and your plane sits on the ramp where temperatures sk= yrocket during the day.=0AThe fuel expands, the float valve closes, and the= wing is structurally damaged=0Aby expanding fuel. The damage may be indica= ted by a big fuel stain on the ramp,=0Athen again it may not be indicated u= ntil you take off.

=0A=0A

 

=0A= =0A

I am somewhat suspect of multiple vents to one ta= nk. I met a=0Abuilder with a BD4. He had doubts about the wing tip vents, s= o he had drilled=0Anumerous holes in his inboard mounted fuel caps. I point= ed out that with=0Agasoline, the fuel vapor concentration is usually above = the combustion limit,=0Abut with the fuel cap in a low pressure region, and= the tip vent getting ram=0Aair, there would be a continuous flow of fresh = air through his tank that could=0Amake it combustible. A static spark near = the vent could set it off. He thought=0Athat was interesting.

=0A=0A

 

=0A=0A

A chec= k valve in the cap allowing air in, not out is probably OK=0Aas long as the= main vent is not in a negative pressure region, but it might allow=0Awater= in while sitting on the ramp.

=0A=0A

 <= /o:p>

=0A=0A

I=E2=80=99m a big fan of the Keep It = Simple principle regarding=0Afuel vents. I only top off a few times a year = for long trips and regard the=0Apossibility of a little spillage taxiing ou= t as a small price to pay.

=0A=0A

=  

=0A=0A

 

=0A=0ARegards,
Bill Hannahan

--0-899988205-1306188271=:91215--