Perry and all, I posted several times in Feb when Paul had his first vapor
lock that the problem was the Facet pump in my opinion.  A Facet pump has a
plunger, cavity, and two check valves and is designed to flow only in one
direction. When the plunger draws back and fills the cavity, the downstream
check valve closes to keep from pulling fuel from downstream and the
upstream valve opens to allow the cavity to fill from the source side. When
the plunger pushes the fuel out, the downstream valve opens and the upstream
valve closes so fuel will flow in the correct direction.

The problem is that Paul normally did not run the pump and relied on gravity
flow, but when the hot fuel pushed bubbles backward in the line, the ck
valve closed and blocked all flow. He did install a vent line, but it was
only 3/16" od (1/8" ID) and must not have been adequate in all circumstances
to vent all the pressure. If the pump had been running, it may have overcome
the vapor and pushed in cool fuel, but I have no idea if the pump was on or
even still configured in the system as before. I would also like to know if
he ever changed to a larger vent line.

If anyone who has seen the wreckage can tell us how the system was
configured when it last failed, that might help us know what not to do.
Herb

> -----Original Message-----
> From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
> Behalf Of Perry Mick
> Sent: Friday, May 27, 2005 4:09 PM
> To: Rotary motors in aircraft
> Subject: [FlyRotary] Re: Sump tank - Velocity version
>
> I'll have to go look at the archives to see what changes Paul made after
> his
> first flame out. One thing different about mine vs. Paul's, is he had
> external pumps and I have internal. I'm still sceptical of this fuel
> heating
> theory, but I'll have to put a temp sensor in my sump tank to prove
> anything
> one way or the other. My sump tank is steel and exposed on the bottom of
> the
> fuselage inside the naca inlet. I touch it after flight and it's stone
> cold.
> With all the hours I have on it, I would say it's well proven by now.
>
> BTW, I've mentioned this on other lists. When doing first flights and
> flight
> testing of canard aircraft, especially with auto conversions, I think one
> should choose an airport to fly out of with multiple, crossing, very long
> runways. Have plans on what you will do if your engine quits soon after
> takeoff from any runway you will use. You can't expect to just hop in an
> experimental plane of this nature and fly it off a short runway as if it
> were a certified plane that has been well proven. You have to expect or
> assume something can go wrong at any time, even the worst possible time.
>
> Back to luring... :)
>
>
> Jim S. wrote:
>
> That gives us two data points. Yours and Paul's first flame out. It's
> entirely possible that Paul did NOT have vapor lock, and never did fix his
> problem. Also possible that there's something else about your system that
> makes it different enough from his to not manifest the problem. I don't
> know. All I can do is the best I can with the data and experience I've
> got ... Jim S.
>
> Jim S. wrote:
>
> There are several down sides to returning fuel to the sump (aggrivated
> quite
> a bit as the size of the sump decreases).
>
> Perry Mick wrote:
>
> Don't know where this comes from? My sump is only 1 gallon and contains
> two
> fuel pumps. Never had an issue with fuel return to the sump in 520 hours
> now.
> I had a minor problem at one time with sump vent placement. Had a
> potential
> major problem once when I had the sump vent temporarily plugged - BIG NO-
> NO!
>
>
>
>
>
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