James,
Sorry to
hear about your problem. I also
have fiberglass fuel tanks on the Cozy, but when I did them, I coated the, with
a sealant made by Jeffco, which is impervious to the various fuels out there. Well, at least the ones they knew about
back in 2002.
I was
pretty careful when I built mine, on getting all of the debris out as well,
though I did check the fuel filters a couple of times in the first 10 hours,
and also replace the one on the primary fuel every year during the conditional
inspection.
I know
that I saw a post earlier by Ernest, who is also building a Delta. He was going with an aluminum tank, I believe,
on his plane.
Steve Brooks
-----Original
Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net]On Behalf
Of James Maher
Sent: Wednesday, December 27, 2006
11:15 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Yet another
limp home story
N11XD Forth
Flight report
The intent of
this flight was to expand the flight envelope a bit from the previous flights
where the aircraft was flown in the center of its envelope. This was also
supposed to be the first flight to retract the landing gear after having
repaired the up-lock release cable.
It was a
somewhat warmer day (mid 50’s F) than the past few flights. By the time I
finished the run-up and was ready for takeoff the coolant temp was up to 110C
but the oil temp was still only 80C. Luckily I was told to position and hold on
runway 2 which allowed the coolant to cool to 100C before I was given takeoff
clearance. There was a 90 degree left cross wind at about 10 knots which, as
soon as I broke ground caused the aircraft to weather vane to the left. It took
lots of right rudder to straighten it out.
It was also
very bumpy close to the ground.
Climb out was
120 MPH at first and then increased to 130MPH to try to improve cooling.
After
leveling off at 2000 feet I headed east to the practice area. The coolant temp
eventually came back down to 90C once in level cruise and the power was
reduced.
Once in the
practice area I climbed to 3000 feet where the air smoothed out a bit and did a
few clearing turns. There were a few other aircraft in the area but they were
in transit away from the practice area. Power was reduced to begin some slow
flight maneuvers. Once the speed came down to about 90MPH the aircraft began to
rock a bit and the controls became a bit "softer". The aircraft also
began to descend slowly.
This is all
normal for a Delta.
It was when I
throttled back up that things began to be "not" normal.
At full
throttle the engine was only making about 50% power.
Here we were,
at 2800 feet and 110MPH, and slowly descending.
I went into
engineering mode trying to diagnose the problem.
I switched
from one fuel pump to the other and the power was further reduced so I went
back to the first fuel pump selected and full power came back … for a little
while.
It then began
to diminish again.
I tried
switching computers, no change.
I disabled
the injectors individually, first the secondarys then the primarys with no
change.
I pulled be
throttle back and power came up a bit but not much.
The engine
was barely making enough power to stay aloft, but it was still making power, so
I headed for my home airport about 18 miles away.
The air/fuel
gauge was all over the place.
At some point
I switched to both fuel pumps and power came up a bit more so I climbed up a
bit.
I was looking
for spots to land but there was not much inviting territory around.
That area is
pretty desolate which is why it is used for a practice area.
The engine
was still running smoothly just not producing much power.
At this power
setting I was able to maintain level flight so I just left it there, not
wanting to make it worse.
At 10 miles
out I radioed the tower that I was inbound.
I was asked
to report a right downwind for runway 2.
At this point
I was mentally preparing for a one shot landing as I would not have sufficient
power for a go- around.
Everything
had to be just right.
I still had a
cross wind to deal with, but was reasonably sure the plane and I could handle
it, if we made it back that far.
The tower
asked for a position report when we were 4 miles out.
At this point
I was thinking that we just might make it back in one piece.
There was
another aircraft entering the airspace at about the same time.
The tower
asked for another position report a few minutes later and I responded with 2
miles after hearing that the other aircraft was 3 miles out. This way I got
preference for sequence even though he was landing on the other runway. I
entered a tight downwind and reported upon turning base. At that point I was
cleared to land. I had to fight a gusty crosswind all the way down final
approach but managed to put it down right on the first part of the runway. I
was then asked by the tower to taxi all the way to the other end of the runway
before exiting. But I didn’t mind.
I was just
glad to be back on earth without incident.
The next day
I went back to try to confirm my suspicions.
During the
summer I had a similar encounter with my car while driving back from the
airport. On the highway in 5th gear the car would only do about
40MPH and about 2000RPM no matter how hard I pressed on the throttle. It turned
out to be a partially clogged fuel filter.
So the first
thing that I looked at on my Delta was the inside of the gascolator.
Sure enough
there was lots of debris in the bottom and on the screen.
It looked
sort of like little fragments of jello.
After
removing the fuel filter it was found to be severely restricted.
I believe
that the new auto fuel formulated with ethanol is causing my fiberglass fuel
tank to slowly disintegrate.
When this
fuel tank was first constructed in 2001 leftover pieces of fiberglass samples
were submerged in fuel to test its long-term effects. Those pieces are still in
tact, but that was the old fuel with MTBE.
The fuel tank
is being used to test the new formulation and it appears that it is failing.
Next project
… perhaps an aluminum fuel tank.
Well back to
the drawing board.
Jim Maher
(Dyke Delta N11XD 13B 4.1 hrs)