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Old January 12th 09, 10:10 PM posted to rec.aviation.products
James M. Knox
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Posts: 30
Default A question about transducer function

waistgunner wrote in
:


In respect to an autopilot system, can anyone describe the path, more so
what happens, from the A/P control in the cockpit to the transducer and
lastly the flight controls?
I know what a transducer does. it converts one form of energy into a
different form The transducer in this system is a pressure transducer.
what type of energy enters the transducer and what does it convert it
to in respect to the A/P system?


[Warning: Extremely simplified answer.]

The pressure transducer is for altitude. The air pressure is converted by
the tranducer to a voltage. This is compared with another semi-fixed
voltage representing the desired altitude. That difference is amplified
and fed by the autopilot to a servo motor to move the control surfaces to
cause a climb (or descent, depending on the sign of the difference).

Similar for direction hold. In the simplest case (wing leveler) a pickoff
from the AH generates a voltage that corresponds to the amount by which the
wings are no longer level (and the sign represents left or right wing dip).
The signal is amplified and fed to aileron servos to move them in a
direction opposite to that of the bank angle. Bingo... the wings level
themselves again.

Add a similar input from a heading bug off the DG and you have heading
hold. Add a voltage from the VOR or GPS deviation and you have tracking.
Variations include roll-rate gyros and accelerometer transducers.


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James M. Knox
TriSoft ph 512-385-0316
1300 Koenig Lane West fax 512-371-5716
Suite 200
Austin, Tx 78756
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