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Subject: RE: [FlyRotary] Re: Bad day at the airport
Date: Tue, 8 Feb 2005 12:10:37 -0600
Message-ID: <87DBA06C9A5CB84B80439BA09D86E69EC07F14@MAIL01.austin.utexas.edu>
Thread-Topic: [FlyRotary] Re: Bad day at the airport
Thread-Index: AcUOBijAN346NWl0Ri2yspjZCgG2SQAAVmaQ
From: "Mark R Steitle" <mark.steitle@austin.utexas.edu>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>

Jim,=20
EFI pumps don't draw very well, but they push great.  I've never seen a
fuel pump with a built-in air bleed.  You'll have to add one to the fuel
circuit, downstream of the fuel pump.  The goal is to get the pump
primed and producing pressure again.  Letting the air bubble out that's
downstream will accomplish this.  To make my air bleed, I tapped the
inside of an AN4 to 1/8" NPT fitting and screwed a motorcycle carburetor
jet into it.  I used 1/4" aluminum tubing with AN4 fittings.  I figured
I could change sizes if the first one didn't work.  I'll take a picture
tonight and post it tomorrow.

Another option would be an electric solenoid with a switch on the panel.
But this isn't as simple a solution as the air bleed and requires the
pilot's intervention at a time when he may be very busy. =20

I decided this was an important change after reading about the
Eggenfelner forced landings, and also of a test flight of a Lancair ES
where they deliberately ran one wing tank dry, then switched to the
other tank.  They almost had to set it down on the interstate due to
this "air-lock" problem.  It finally caught at the last minute.  Not
good. =20

Mark S.     =20

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Jim Sower
Sent: Tuesday, February 08, 2005 11:46 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Bad day at the airport

Marc,
That's interesting.  I can't visualize how it wouldn't blow all the=20
vapor through the fuel rail and injectors (they will pass a lot more air

than fuel, even at lower pressure) but I have to accept that it=20
happened.  How do you determine if a pump has a bleed circuit?  If not,=20
or if you're not able to make the determination, would a small (1/8" OD=20
line) downstream from the pump (perhaps at a high point in the fuel=20
path) bypassing the regulator to the return line work?=20

Inquiring minds need to know ... Jim S.

Mark R Steitle wrote:

>Paul,
>Do you have a bleed circuit between your pump and fuel pressure
>regulator? Do you have heat shields on your fuel lines? My guess is
that
>you may have experienced vapor lock.  Without a bleed circuit, the fuel
>pump can't produce enough pressure to overcome the fuel pressure
>regulator.  I discovered this in my fuel system, as did some builders
on
>the Eggenfelner group.  They actually had a couple of forced landings
>attributed to vapor lock.  I could reproduce this condition by letting
>my fuel pump suck air for a couple of seconds, then reinsert the pickup
>back into the tank.  This was to simulate running a tank dry, and then
>switching to the other tank.  With air in the lines, the pump couldn't
>overcome the back pressure from the regulator.  Only way to get it to
>run again was to crack the line to the injectors (with pump running)
>until the pump re-primed.  The bleed circuit allows this.  It has a
>.020" orifice, so it doesn't pass an excessive amount of fuel, but it
>will pass quite a bit of air.  Now, if I pull the pickup out of the
tank
>and reinsert it, the pump will reprime in a few seconds.  In your case,
>I suspect that once you landed, there was enough time for engine/fuel
>system to cool enough to allow a restart.  Just a guess. =20
>
>Mark S. =20
>(Glad you weren't hurt, or the a/c either)   =20
>
>-----Original Message-----
>From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
>Behalf Of Ernest Christley
>Sent: Tuesday, February 08, 2005 8:16 AM
>To: Rotary motors in aircraft
>Subject: [FlyRotary] Re: Bad day at the airport
>
>Paul wrote:
>
> =20
>
>>    =20
>>    Thanks, Bill....My next step is to pull the cowling and check
>>    plugs, filters, etc.  I will inspect the plugs to see what
>>    condition they are in. That can tell me a lot. I wish I hadn't
>>    re-started the engine to taxi back to the hangar. Running the
>>    engine after the problem might have covered up the problem, as it
>>    seemed to be running better on the taxi trip back to the hangar.=20
>>    I'll report back with my findings.  Take care, and many thanks to
>>    everyone for their input and suggestions.  Paul, I'd rather be
>>    flying, Conner
>>    =20
>>
>>   =20
>>
>Paul, I got excited just reading your account.  Glad you and your plane

>are still in one piece.
>
>Just to add to Bill's suggestion, the first car I owned was...let's
say,
>
>'previously owned'.    Occasionaly, when you tried to get on the gas to

>hard, it would die.  Always cranked right back up.  The problem went=20
>away when I rebuilt the carb to clean out all the trash that would get=20
>sucked up and block the jets (only when you really needed it not to).
>
> =20
>
>>> Homepage:  http://www.flyrotary.com/
>>> Archive:   http://lancaironline.net/lists/flyrotary/List.html
>>>     =20
>>>
>
> =20
>
>>> Homepage:  http://www.flyrotary.com/
>>> Archive:   http://lancaironline.net/lists/flyrotary/List.html
>>>     =20
>>>
>
>
> =20
>

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