|
|
I would like to share an experience I had with what I believe is a fuel line
vent problem on my ES.
I was flying out of Manteo, NC last week on a very damp but sunny morning,
so damp the moisture formed again about as fast as we could dry it. I used a
squeegee to clean the water off of the wings and wiped the wings parallel to
the cord. (I usually wipe perpendicular to the cord.) My wife was following
with a cloth to wipe the wing/horizontal stabilizer dry. We probably did not
do a good job of wiping the water from the bottom of the wing.
We left the airport about 08:30 local time and flew through the typical
coastal high humidity hazy conditions. I took off with the boost on low and
left it on until the top of the climb. Level at 8500 feet I turned the low
boost off and the pressure and gas flow went to zero quickly. Turned the low
boost on and everything was ok.
After some thought, I believed I had a diaphragm break in the mechanical
fuel pump or a plugged vent line. I told my wife I was going to run an
experiment, switched tanks while the boost was on. Everything was
"hunky-dory" so now I switched the fuel pump off. Gas pressure and flow went
to zero, turned the boost back on and everything was normal. Ah Ha - a
broken diaphragm.
The "one who must be obeyed" then said "Don't touch that damn switch again!"
so no more experimenting.
After landing and on the taxiway I shut off the fuel pump and everything was
normal - no broken diaphragm. Shut down and on Monday started back up with
no fuel pump, taxied to the local shop and took the cowl of to see if
anything was loose. Every thing was tight and I talked to the local
mechanic. He said what I was explaining could not happen, but it did!
We taxied with no fuel pump on and did the run-up without boost. We took off
for home with the fuel pump on and I was not allowed to experiment for the
entire boring 5 hour flight. We left the fuel pump on all the way per
demand/request.
At home I again took the cowl off and could find nothing. Reassembled and
flew the plane in the pattern with fuel pump on until 1500' AGL (6500'). I
shut the fuel pump off @ 6500' and climbed to 8300'. Everything worked as
expected. WHAT IS GOING ON?
I suspect we got a small amount of water near/in the NACA scoops on the
ground in NC. As we took off there was a water film/bubble in each of the
vents that created a small vacuum in the tanks that could be overcome by the
electric fuel pump but not the mechanical one. I know from previous
experience that the mechanical fuel pump on my airplane will not prime
itself but will maintain 8 to 34psi depending on RPM after it is primed.
Is there a better explanation??
Eugene Long
Lancair Super ES
glong2@netzero.net
-----Original Message-----
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of John
Huft
Sent: Wednesday, May 09, 2007 9:28 AM
To: lml@lancaironline.net
Subject: [LML] Re: IO-550 fuel injection
Here is an off-the-wall theory from the RV spy....
I am suspicious of those cute little NACA vents you guys use for tank
vents. I am thinking they may not be as effective as they need to be at
higher altitudes (lower indicated airspeeds). I think maybe NACA vents
work better when there is airflow through them, rather than being used
to generate a static pressure. ------
|
|