David Megginson wrote:
 > Andy Ross writes:
 > > All that being said, did the configuration patch for the takeoff RPMs
 > > do what you want?  It was better justified than the idle hack. :)
 >
 > The plane seems to take off OK, but there are handling problems -- in
 > a 72kt climb at full power, the nose pulls so strongly to the left
 > that even full right rudder deflection cannot compensate.

This effect must be independant of the recent patch, no?  None of that
would have affected trim conditions.  It seems like this comes up
again and again (in JSBSim too) as a consistent bug report.  It's
really not a bug.  It's just that real aircraft correct for the effect
in ways that the simulator doesn't.

In this case, the pull you are seeing is the engine torque.  It is a
rolling moment, not a yaw, and thus you want to be correcting against
it with aileron trim, not rudder.  The 172 has very little (zero, in
the current model) dihedral, and therefore there is almost no coupling
between yaw and roll.  On a real aircraft, this is compensated for by
asymmetry to the wings, control surfaces, a can't to the engine, or
all three.  That is, it has a "baked in" trim.

One option would be to experiment to acheive a value for aileron trim
that worked well at cruise, and set that in the aircraft xml file.  A
cooler option would be to make the solver do it, but that requires
code.

Andy

-- 
Andrew J. Ross                NextBus Information Systems
Senior Software Engineer      Emeryville, CA
[EMAIL PROTECTED]              http://www.nextbus.com
"Men go crazy in conflagrations.  They only get better one by one."
  - Sting (misquoted)


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