X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao09.cox.net ([68.230.241.30] verified) by logan.com (CommuniGate Pro SMTP 5.0.9) with ESMTP id 1094478 for flyrotary@lancaironline.net; Sat, 06 May 2006 10:30:13 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.30; envelope-from=ALVentures@cox.net Received: from BigAl ([72.192.132.90]) by fed1rmmtao09.cox.net (InterMail vM.6.01.06.01 201-2131-130-101-20060113) with ESMTP id <20060506142925.PUKF24290.fed1rmmtao09.cox.net@BigAl> for ; Sat, 6 May 2006 10:29:25 -0400 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: Fuel system pressure bleed off Date: Sat, 6 May 2006 07:29:42 -0700 Message-ID: <000001c67119$83b3fd50$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C670DE.D7552550" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: <87DBA06C9A5CB84B80439BA09D86E69E01D6C66D@MAIL01.austin.utexas.edu> X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2869 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C670DE.D7552550 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Subject: RE: [FlyRotary] Re: Fuel system pressure bleed off =20 Hi Bill... Welcome back. =20 The bleed circuit came about as a result of two Eggenfellner Subaru accidents/incidents traced to fuel starvation. They hashed it over on = the Subaru group and the simplest solution was to add a bleed circuit = between the fuel rail and the return line (bypassing the pressure regulator), allowing any trapped air to be easily forced out of the system. = Preventing "weeping" of the injectors was a secondary benefit. =20 The need for a bleed is dependant on fuel system design. If you can be = sure that there is fuel at the pump inlet for re-prime, then there is no need = for a bleed. IOW, if there is any point in the line upstream from the pump = that is higher than the pump, there is potential for a bubble of trapped air. Air at the pump inlet may not allow the pump to force any flow through = the pressure regulator. =20 A good way to avoid injector 'weeping' (which would only happen on a = faulty injector), or residual pressure in the rail, is shutoff the pump first = in your shutdown sequence. =20 At least that's my opinion . . . =20 Al =20 =20 ------=_NextPart_000_0001_01C670DE.D7552550 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Subject: RE: [FlyRotary] Re: Fuel system pressure bleed off

Hi Bill... Welcome back.

The bleed circuit came = about as a result of two Eggenfellner Subaru accidents/incidents traced to fuel starvation. They hashed it over on the Subaru group and the = simplest solution was to add a bleed circuit between the fuel rail and the return = line (bypassing the pressure regulator), allowing any trapped air to be = easily forced out of the system. Preventing "weeping" of the = injectors was a secondary benefit.

The need for a bleed is dependant = on fuel system design. If you can be sure that there is fuel at the = pump inlet for re-prime, then there is no need for a bleed. IOW, if = there is any point in the line upstream from the pump that is higher than the = pump, there is potential for a bubble of trapped air. Air at the pump = inlet may not allow the pump to force any flow through the pressure = regulator.

A good way to avoid injector = ‘weeping’ (which would only happen on a faulty injector), or residual pressure in = the rail, is shutoff the pump first in your shutdown = sequence.

At least that’s my = opinion . . .

Al

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