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To keep things straight, the follow-up message and attachment was for Bob
Perkinson's RV-9.
Mark S.
Lancair ES - 20B
At 09:45 AM 5/27/2004 -0500, you wrote:
- ----- Original Message -----
- From: Bob Perkinson
- To: Rotary motors in
aircraft
- Sent: Thursday, May 27, 2004 9:09 AM
- Subject: [FlyRotary] Re: Fuel Pump Design
- The attached drawing is my idea of a simple fuel system for the 9a
that I am building, with Aux fuel tanks akin to Berne Kerr?s
Project. I would like some feed back as to what problems this
arrangement might pose, and what the remedy would be for such
problems. The plan is to use large diameter pipe between the main
fuel tanks so as to allow the fuel to equalize
- Bob Perkinson.
- -----Original Message-----
- From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net]On
Behalf Of Mark Steitle
- Sent: Tuesday, May 25, 2004 3:06 PM
- To: Rotary motors in aircraft
- Subject: [FlyRotary] Fuel Pump Design
- Fuel system design hasn't come up in quite a while. But since a
large portion of accidents are fuel related, I thought this would be
worthy of discussion.
- I have experienced a failure mode during ground runs on my Lancair ES
with 20B that seems to be a problem with other types of installations as
well. I recently read a first flight report by a professional test
pilot, David Allen, that almost had to set a Lancair ES, N711RG, down on
I-70 due to the inability to restart the engine after running a tank
dry. (See
www.geocities.com/daveandjj for the full
story.) This was a certified fuel-injected engine
installation. Also, the Subaru guys (I have been lurking on the
Eggenfelder Subie site today) had a similar situation, resulting in some
glider time and a dead-stick landing.
- The problem is that after exhausting the fuel in one tank an airlock
forms between the fuel pump(s) and the fuel pressure regulator that the
efi pump cannot overcome due to lack of fuel in the supply line.
This is what I have experienced with my installation on ground
runs. I can't get the efi pumps to re-prime unless I momentarily
break a line loose between the pump outlet and the pressure
regulator. As soon as I do that the pump will re-prime and all is
well.
- For the record, I have two of Tracy's efi pumps, with two efi
filters, hooked in parallel. They are mounted low on the fire
wall. Upstream is a gascolator and an Andair 6-port selector
valve. Downstream of the pumps/filters is a map sensing pressure
regulator. There is a -6AN going to the fuel rail, and a -4 return
line back to the Andair valve/tank.
- I was curious if anyone else has had this happen and what they did to
resolve the issue. I have come up with two possible
solutions.
- 1. Tee off the pump output and put an electric solenoid valve
in the line and tee the outlet of the solenoid to the fuel return line,
past the regulator. Push-button switch on panel would activate the
solenoid. If needed, a second or two of activation should relieve
the air-lock and allow the pumps to re-prime.
- 2. Install a bleed line around the pressure regulator with a
small metering orifice (.020-.030") that would bleed off any air
that might get trapped. (This appears to be the solution the Subaru
group is focusing on). This would be a full time bypass. This
seems to be the simpler solution.
- 3. Install a low pressure, high volume fuel pump in one, or
both, of the wing tanks. Procedure would be to always keep reserve
fuel in this tank.
- Any comments from seasoned flyers would be welcomed.
- Mark S.
Hi, Mark.....looking at the drawing, I noted that there are two
spring loaded ball check valves after the two fuel pumps. In order
to possibly simplify the installation, might I suggest using fuel pumps
such as the MSD high pressure fuel pumps, as they already have a built-in
check valve inside each pump. I am unfamiliar with Tracy's pumps, so I
don't know if his has the check valve built into it as well?
Paul Conner
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