Return-Path: Received: from mail20.syd.optusnet.com.au ([211.29.132.201] verified) by logan.com (CommuniGate Pro SMTP 4.3c1) with ESMTP-TLS id 729254 for flyrotary@lancaironline.net; Tue, 15 Feb 2005 00:57:02 -0500 Received-SPF: none receiver=logan.com; client-ip=211.29.132.201; envelope-from=lendich@optusnet.com.au Received: from george (d211-31-87-63.dsl.nsw.optusnet.com.au [211.31.87.63]) by mail20.syd.optusnet.com.au (8.12.11/8.12.11) with SMTP id j1F5uCK8011212 for ; Tue, 15 Feb 2005 16:56:13 +1100 Message-ID: <004201c51323$5f9831c0$3f571fd3@george> From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Jet Pump Date: Tue, 15 Feb 2005 15:58:29 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_003F_01C51377.30EB9A70" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 This is a multi-part message in MIME format. ------=_NextPart_000_003F_01C51377.30EB9A70 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Yep Ed! Sure does. The one concern of Tracy's very simple direct system, was the transfer = system - I suppose you could have a hand pump back-up. At this point in time, I'm thinking ( for a low wing design) a small = exterior sump tank (under the pilot), Gravity fed ( maintaining equal = fuel distribution from both tanks - like a water level) with duel pumps = inside the sump tank, which is vented to one or both wing tanks. Being exterior it's easier to get at for maintenace and repair, no probs = with fuel in the cockpit or fumes and kept cool. George (down under) George, its actually a siphon pump for a two tank system. They use = the fuel being released by the fuel pressure regulator in one tank and = run it through a restriction ( a Ventura) and it flows through the = Ventura (returning back into the main tank) it develops a low pressure, = this low pressure region of the jet is plumbed to the second tank. The = "suction" action pulls fuel from the second tank into the main tank = where the EFI pump, "Jet pump" and fuel pressure regulator are all = located. This is used as a "transfer" pump but does not require another = "electric" pump such as a facet pump that many of us use as either a = boost pump or fuel transfer pump. Interesting concept for sure - but if = for some reason something would break the "siphon" effect (say trash in = the Ventura) then NO fuel transfer from the second tank. But, then a = transfer pump can fail as well - sigh nothing never breaks {:>) Hope this explains it well enough. Ed A ----- Original Message -----=20 From: George Lendich=20 To: Rotary motors in aircraft=20 Sent: Monday, February 14, 2005 9:01 PM Subject: [FlyRotary] Re: Fuel System Design - Jet Pump Mark/Ed, What's a Jet pump? George ( down under) Good Idea, Mark I think that people get pretty hung up and adamant about certain = things - even though they may indeed work. While all fuel systems = clearly require careful design and construction attention, some appear = to require even more scrutiny. What I think sometimes gets folks in = trouble is they "copy" a design they have seen/hear works. However, = they seldom ever copy the design faithfully either due to = space/configuration constraints - or they have an "improvement" to it. = The bottom line is the system has changed, "Yes, Virginia, it may really = matter as to whether the pickup is at the top vs the bottom, etc. ". Even Tracy's system can byte you if you are not careful. You must = pay attention to fuel transfer or you can end up with the return fuel = pushing out the vent of the return tank. So while I do believe his = design eliminates (or certainly diminishes the chance of vapor lock) - = you now must carefully monitor how much fuel is in the return tank. I = believe Tracy uses a facet pump to move fuel from one tank to the other = - which even though unlikely, could fail leaving fuel unavailable. I = would have to agree though that scenario certainly would leave you a bit = more time to consider your options - than a faltering engine on take = off.=20 But, yes, it would appear that the "jet pump" might indeed be a = replacement for the facet pump. Interesting concept. Ed A =20 ----- Original Message -----=20 From: Mark R Steitle=20 To: Rotary motors in aircraft=20 Sent: Monday, February 14, 2005 4:40 PM Subject: [FlyRotary] Fuel System Design - Jet Pump Ed,=20 Thanks for that excellent article on fuel system design. In = reading through it, on page 5, I came to the description of the jet pump = and had a thought (that alone is a scary thing). I was thinking that = this could be used to eliminate the need for the facet pump in a design = such as Tracy's which would simplify things even more than Tracy's = system already does. Of course, as in Tracy's design, this would = eliminate the need for the fuel selector valve too. As it was designed = to do, the Jet Pump would be powered by excess fuel from the main fuel = pump located in the left tank. Fuel from the other (right) wing tank = would be drawn into the main (left) tank by the Jet Pump. To prevent = overfilling the main tank, transfer could be controlled by a small = solenoid valve. Since you would be drawing fuel from the right tank = pretty much all the time, it may be possible to route the return fuel to = the right tank. I guess this idea could also be used with a sump tank. = Time for a sanity check. =20 =20 Mark S. =20 =20 ------=_NextPart_000_003F_01C51377.30EB9A70 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Yep Ed!
Sure does.
The one concern of Tracy's very simple = direct=20 system, was the transfer system - I suppose you could have a hand pump=20 back-up.
 
At this point in time, I'm thinking ( = for a low=20 wing design) a small exterior sump tank (under the pilot), Gravity fed ( = maintaining equal fuel distribution from both tanks - like a water = level) with=20 duel pumps inside the sump tank, which is vented to one or both wing=20 tanks.
 
Being exterior it's easier to get at = for maintenace=20 and repair, no probs with fuel in the cockpit or fumes and kept=20 cool.
 
George (down under)
George, its actually a siphon pump = for a two tank=20 system.  They use the fuel being released by the fuel pressure = regulator=20 in one tank and run it through a restriction ( a Ventura) and it = flows=20 through the Ventura (returning back into the main tank) = it develops a low=20 pressure, this low pressure region of the jet is plumbed to the second = tank.  The "suction" action pulls fuel from the second tank into = the main=20 tank where the EFI pump, "Jet pump" and fuel pressure regulator are = all=20 located.  This is used as a "transfer" pump but does not require = another=20 "electric" pump such as a facet pump that many of us use as either a = boost=20 pump or fuel transfer pump. Interesting concept for sure - but if for = some=20 reason something would break the "siphon" effect (say trash in the = Ventura)=20 then NO fuel transfer from the second tank. But, then a transfer = pump can=20 fail as well - sigh nothing never breaks {:>)
 
Hope this explains it well = enough.
 
Ed A
----- Original Message -----
From:=20 George Lendich
To: Rotary motors in = aircraft=20
Sent: Monday, February 14, = 2005 9:01=20 PM
Subject: [FlyRotary] Re: Fuel = System=20 Design - Jet Pump

 
Mark/Ed,
What's a Jet pump?
George ( down under)
 
Good Idea, Mark
 
I think that people get pretty = hung up and=20 adamant about certain things - even though they may indeed=20 work. While all fuel systems clearly require careful design = and=20 construction attention, some appear to require even more = scrutiny. =20 What I think sometimes gets folks in trouble is they "copy" a = design they=20 have seen/hear works.  However, they seldom ever copy the = design=20 faithfully either due to space/configuration constraints - or they = have an=20 "improvement" to it.  The bottom line is the system has = changed,=20 "Yes, Virginia, it may really matter as to whether the pickup is = at the=20 top vs the bottom, etc. ".
 
Even Tracy's system can byte you = if you are=20 not careful.  You must pay attention to fuel transfer or you = can=20 end up with the return fuel pushing out the vent of = the return=20 tank.  So while I do believe his design eliminates (or = certainly=20 diminishes the chance of vapor lock) - you now must carefully=20 monitor how much fuel is in the return tank.  I=20 believe Tracy uses a facet pump to move fuel from one tank to = the=20 other - which even though unlikely, could fail leaving fuel=20 unavailable.  I would have to agree though that scenario = certainly=20 would leave you a bit more time to consider your options - than a=20 faltering engine on take off. 
 
But, yes, it would appear = that the "jet=20 pump" might indeed be a replacement for the facet pump.  = Interesting=20 concept.
 
Ed A 
----- Original Message ----- =
From:=20 Mark R = Steitle
To: Rotary motors in = aircraft=20
Sent: Monday, February = 14, 2005=20 4:40 PM
Subject: [FlyRotary] Fuel = System=20 Design - Jet Pump

Ed,=20

Thanks for that = excellent=20 article on fuel system design.  In reading through it, on = page 5, I=20 came to the description of the jet pump and had a thought (that = alone is=20 a scary thing).  I was thinking that this could be used to=20 eliminate the need for the facet pump in a design such as = Tracy=92s which=20 would simplify things even more than Tracy=92s system already = does. =20 Of course, as in Tracy=92s design, this would = eliminate=20 the need for the fuel selector valve too.  As it was = designed to=20 do, the Jet Pump would be powered by excess fuel from the main = fuel pump=20 located in the left tank.  Fuel from the other (right) wing = tank=20 would be drawn into the main (left) tank by the Jet Pump.  = To=20 prevent overfilling the main tank, transfer could be controlled = by a=20 small solenoid valve.  Since you would be drawing fuel from = the=20 right tank pretty much all the time, it may be possible to route = the=20 return fuel to the right tank.  I guess this idea could = also be=20 used with a sump tank.  Time for a sanity check. =20

 

Mark S.=20    

 

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