RE: Europa-List: Long wing CG

[Peter Zutrauen <peterz@zutrasoft.com>]

Hi Dave,

Congrats again your successful flight testing!  Oh for me to dream....  :-)

I remember in my glider ride, that John had her trimmed up at around 45-50mph 
indicated
(I did not look if he had any more up-trim left - but he didn't just
push the trim to it's limit).... I wonder what that plane's cg is at? did you
chat with John?  What trim speeds did you get in the demo?

Cheers & best of continued success!
Pete
A239 Ottawa

        -----Original Message----- 
        From: DJA727@aol.com [mailto:DJA727@aol.com] 
        Sent: Fri 2/7/2003 11:23 AM 
        To: europa-list@matronics.com 
        Cc: 
        Subject: Europa-List: Long wing CG
        
        

        
        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