David Megginson wrote:
> I noticed that all of the YASim models tended to nose down with
> neutral elevator. I assumed that it was a W&B problem and tried
> shifting weight all over the place in the J3 cub (and even moved the
> wings around), but nothing fixed the problem.
Right. The solver just compensated for the changes with extra tail
incidence. :)
> In the end, I figured out that the YASim solver simply did not know
> where to put the elevator for cruise. We know that the elevator is
> normally near to a neutral position (or slightly forward) for light
> aircraft, but YASim doesn't.
This came up a while back. Apparently I didn't put it in the docs. A
slightly terser explanation is this:
YASim trims the aircraft (with tail incidence, not control input) so
that the elevator value is exactly zero in the specified cruise
configuration. It assumes zero trim input by default. Use a control
setting for the proper value of elevator-trim in the cruise
parameters.
You set the elevator property instead, which of course has the same
effect. I'd argue that setting trim is easier to understand, and
closer to what is really happening in the cockpit. If a pilot knows
that the aircraft cruises with 30% nose-down trim, they can just plug
that value in. Pilots are probably less likely to know the elevator
deflection required when the trim is at the zero point.
Andy
--
Andrew J. Ross Beyond the Ordinary Plausibility Productions
Sole Proprietor Beneath the Infinite Hillsboro, OR
Experience... the Plausible?
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