In a message dated 2/7/2003 5:45:21 AM Pacific Standard Time,
graham@gflight.f9.co.uk writes:
> Mini U2 test pilots
> Dave
> It sounds as though either your trim is not correct or the CG is too far
> forward. I would stick with holding the tail down and let it go forward
> smoothly exactly as Joim Nelson and Dave Watts say. Judge it by feel. If
> stick force is high trim might be too far forward, but CG might affect
> that. I would persuade Andy Draper to coach you on that , maybe John Hurst
> too, I would guess John has more U2 experience than any of us.
>
> One thing I found, all aircraft are different in some respects, even
> airplanes of the same type. Our Classic short wing had too different trim
> positions, one for landing and one for take off, I approached at 60 kts,
> (55 if dead calm. Gives a steeper approach) if full power was selected we
> had to trim forward a lot or the airplane got below the glide stall speed,
> if the engine quits in that flight condition you have real trouble. Other
> Classics had no trim change with power change.
>
> One other thing, as Jim? remarked as you flare the nose tends to drop due
> to the ground effect of the wing altering airflow direction over the tail
> (less with tri gear, not as close to the ground) effectively a nose down
> pitch trim change. You must keep the stick firmly in your belly once the
> tailwheel is on the ground.
>
> Take it very carefully, change one thing at a time and wish I was in your
> situation right now! {{:-)
> Graham
Thanks Graham,
The word is definitely that the CG is too far forward for the long wing. That
is what is flies like and that is what Europa found with their demonstrator
aircraft. One tidbit of information I gained from talking to Andy was that if
elevator authority is questionable, you can gain some authority by not
trimming to the slow approach speed and holding some back pressure during the
approach instead. The trimming out of the speed causes you to lose some
control authority. I reviewed my video tape from the cockpit and found that
the stick position was quite aft for the speed I was flying when touching
down - main first slightly - too fast. I checked the trim system again and
found all measurements to be in order. It looks as though if you are going to
fly both wings, you need to have a compromise CG to work with the 2 wings.
Right now, I can say that 59.5 appears to be the forward limit for the long
wings, and may actually be 60.0 depending on what is considered an acceptable
flight characteristic.
The CG has been adjusted to 60.5 for the next flight. I suspect it will be
easier to plant the tailwheel on the ground with better pitch authority at
the slower speeds.
Baby steps!
Dave
A227
Mini U2
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