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When using the autopilot, the function(s) of the automatic pitch trim is (are) to:

1 – off-load any steady state elevator deflection
2 – ease the steady state load of the rudder as much as possible
3 – cancel out of trim force during autopilot disengagement.

The combination that regroups all of the correct statements is:

  • A
    1.
  • B
    2, 3.
  • C
    1, 3.
  • D
    1, 2.
The automatic pitch trim is used to:
  • ensure the airplane is properly trimmed when the autopilot is disengaged.
  • permits the elevator to always be in neutral position with respect to the horizontal stabilizer. In other words, it off-loads any steady state elevator deflection.
When the autopilot is engaged, the role of the automatic pitch trim is to relieve the autopilot servo motor and return the aircraft in-trim when disconnecting the autopilot. It basically provides a smooth ‘HAND-OVER’ when disengaging the autopilot.
Caution! Do not confuse the auto trim with the automatic synchronization function which is providing a smooth `TAKE-OVER` when engaging the autopilot. The auto synchronization function will prevent the autopilot engagement it is inoperative, as this might result in an abrupt snatch and jerks of the autopilot during engagement.

For an airplane fitted with a mechanical flight control system, the automatic pitch trim system is active whenever the autopilot is engaged. On the other hand, when flying a fly-by-wire aircraft, the automatic pitch trim is always active either you are flying it manually or with the autopilot engaged. When flying an FBW aircraft manually, the system eliminates the need for the pilot to make control column inputs (or manual trim) to compensate for flight path parameter alterations such as thrust changes, landing gear configuration changes, or slats/flaps configuration changes.

Summary:
`HAND-OVER` - automatic pitch trim function.
`TAKE-OVER` - automatic synchronization function.

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