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Old May 28th 08, 05:10 AM posted to rec.aviation.piloting,rec.aviation.student
Ken S. Tucker
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Posts: 442
Default Pitch vs. trim in flight phases

On May 27, 7:42 am, wrote:
On May 16, 1:49 pm, "Ken S. Tucker" wrote:

I was ok with the location of the trim wheel, but the adjustment
was too coarse for me, but I could be a bitchy sissy.
My wheel was graduated, with a zero mark and did not quite
give the fine adjustment I wanted. That could be cables out
to the tail, I should have learned the mechanism!


Nothing to do with the cables. Cessna's trim is anything but
sensitive, having four or five full turns of the wheel for the trim
range. Try a Citabria sometime, where the trim is a lever that moves
about eight or ten inches for the full range. Much more twitchy.

As far as others have asked about sim trim, the good,
commercial training sims (Level II) have a pitch control mechanism
centered by some strong springs that supposedly simulate elevator
pressures. The anchor points for those springs are movable, and those
are what the trim mechanism moves. So in slow flight the yoke is well
back, against the springs, so that the trim moves the spring anchors
back until the pressure disappears. The yoke does not move and the
pilot, if he's "flying" right, doesn't let it move. He just trims off
the pressure. Mx's stick, on the other hand, trims electronically so
that he has to gradually center the stick to keep the nose where it's
supposed to be. Not realistic at all. And the springs in those cheap
things are so feeble as to be a joke. Flying the real airplane is much
more work. If you had realistic spring forces you'd have to bolt the
stick to the desk and anchor the chair to the floor.
I built our own procedures sim here. Proper frame welded up,
proper adjustable seat, huge monitor, real rudder pedals with
realistic spring feel, real stick with a heavy non-discrete center
spring and an adjustable anchor to simulate a reaslistic trim. Real
steel throttle/prop/mixture quadrant. Robbed the electronics out of
the CH stick and pedals to drive it.
But still, it's used only as a procedures trainer, not for teaching
how to fly. The students use it for free to practice what they learned
on our certified Elite sim or in the air under the hood. It's much
more work to fly it, thanks to the big springs I put in it. I need to
redesign the mechanical trim to get more travel, though.
Underestimated the degree of elevator movement between high cruise and
slow flight.
And it has a collective for helicopter flight.

Dan


IIRC you (Dan) are in Sask, I'm just over the hills
in BC. If we're ever going by your place I'd love to
try that sim, how much do you charge?
Ken