Return-Path: Received: from [24.25.9.102] (HELO ms-smtp-03-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 3082979 for flyrotary@lancaironline.net; Wed, 17 Mar 2004 11:11:00 -0500 Received: from edward (clt78-020.carolina.rr.com [24.93.78.20]) by ms-smtp-03-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id i2HGAvs2011161 for ; Wed, 17 Mar 2004 11:10:59 -0500 (EST) Message-ID: <000801c40c3a$70443050$2402a8c0@edward> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Automatic Fuel pump backup Date: Wed, 17 Mar 2004 11:11:00 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0005_01C40C10.872DC3F0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1158 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0005_01C40C10.872DC3F0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable ----- Original Message -----=20 From: Al Gietzen=20 To: Rotary motors in aircraft=20 Sent: Wednesday, March 17, 2004 9:36 AM Subject: [FlyRotary] Re: mainfold hose Perry wrote: If you are flying and running only one h.p. fuel pump, and that pump = fails, the engine will become silent only milliseconds later!=20 This is interesting. As my circuit diagram is currently configured, I = have a pressure switch in the fuel system which automatically turns on = the backup pump if the pressure drops below about 30 psi. (don't = remember now the exact setting on the pressure switch). Do you suppose = that this wouldn't react fast enough to keep the engine running? There is a manual bypass so I can turn the pump on if I want. The = idea was to turn on both pumps for takeoff, but at other times the = backup would automatically kick in to keep the engine from stopping if = the primary pump stopped; thereby avoiding rapid heart rates on the part = of pilot and passengers. Al Al, I think that your set up should preclude rapid heart rates for the = most part. Being a switch, if it is set for around 30 psi fuel pressure = then your back-up pump should kick in immediately if pressure falls = below that point. With a pump that can pump 45 lbs/hour or 4.5 = gallons/min at 43 psi then it should not take it any appreciable time to = fill and repressurize the fuel rails and hoses.=20 I am assuming you are using AN-6 lines and assuming you have a total = of 4 feet of it in your high pressure part of your fuel system. Then at = 3/8" ID you have approx 5.3 cubic inches (if it were completely empty - = which it shouldn't be when you backup pump kicked on) that amounts to = around 0.02294 gallons. So at 4.5 gallons/min the time to fill that = volume would be 0.02294/4.5 =3D 0.0051 minutes or around 0.306 seconds. = And that is if the pump turned on after the lines were completely = empty. So I don't think you would notice it during normal operations. = You might notice the engine changing tone as the fuel mixture started to = lean but I think that would be about it. Ed Anderson ------=_NextPart_000_0005_01C40C10.872DC3F0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
----- Original Message -----
From:=20 Al = Gietzen=20
Sent: Wednesday, March 17, 2004 = 9:36=20 AM
Subject: [FlyRotary] Re: = mainfold=20 hose

Perry = wrote:

 

If you are flying and running only one h.p. = fuel pump,=20 and that pump fails, the engine will become silent only milliseconds = later!=20

 

This is=20 interesting.  As my circuit diagram is currently configured, I = have a=20 pressure switch in the fuel system which automatically turns on the = backup=20 pump if the pressure drops below about 30 psi. (don=92t remember now = the exact=20 setting on the pressure switch).  Do you suppose that this = wouldn=92t react=20 fast enough to keep the engine running?

 

  = There is a=20 manual bypass so I can turn the pump on if I want.  The idea was = to turn=20 on both pumps for takeoff, but at other times the backup would = automatically=20 kick in to keep the engine from stopping if the primary pump stopped; = thereby=20 avoiding rapid heart rates on the part of pilot and=20 passengers.

 

Al

 

Al,

 

   =20 I think that your set up should preclude rapid heart rates for the = most=20 part.  Being a switch, if it is set for around 30 psi fuel = pressure then=20 your back-up pump should kick in immediately if pressure falls below = that=20 point.  With a pump that can pump 45 lbs/hour or 4.5 gallons/min = at 43=20 psi then it should not take it any appreciable time to fill and=20 repressurize the fuel rails and hoses. 

 

 I = am=20 assuming you are using AN-6 lines and assuming you have a total of 4 = feet of=20 it in your high pressure part of your fuel system.  Then at 3/8" = ID you=20 have approx 5.3 cubic inches (if it were completely empty - which it = shouldn't=20 be when you backup pump kicked on) that amounts to around 0.02294=20 gallons.  So at 4.5 gallons/min the time to fill that volume = would be=20 0.02294/4.5 =3D 0.0051 minutes or around 0.306 = seconds.   And=20 that is if the pump turned on after the lines were completely = empty.  So=20 I don't think you would notice it during normal operations. You = might=20 notice the engine changing tone as the fuel mixture started to lean = but I=20 think that would be about it.

 

Ed=20 Anderson

 

 

------=_NextPart_000_0005_01C40C10.872DC3F0--