----- Original Message -----
Sent: Wednesday, December 27, 2006 11:15
PM
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)