Stabilizer

[TotalBeginner]

Can anyone help me out

I am trying to understand exactly how the stabilizer is used on modern airliners to keep the aircraft in trim.

I understand the concept of trim tabs used on light aircraft to remove control forces, but moving the whole stabilizer will surely have no affect on the neutral position of the stick if the evevators are connected to it?

e.g. If the control column is left in the neutral position, but the stab is moved up or down. Will the elevator remain flush with the stabilizer or will it remain flush with the longitudinal axis of the aircraft???

Does Stab Trim feel the same as elevator trim in light aircraft? i.e If the control column is held back to maintain a given attitude, does moving the stab remove the aerodynamic force, or does the control column then have to be released back to the neutral position once the aircraft is in trim???

[catchup]

* but moving the whole stabilizer will surely have no affect on the neutral position of the stick if the evevators are connected to it?*
A: Indeed

*e.g. If the control column is left in the neutral position, but the stab is moved up or down. Will the elevator remain flush with the stabilizer or will it remain flush with the longitudinal axis of the aircraft???*

A: Elevator remains flush with stabilizer.

*Does Stab Trim feel the same as elevator trim in light aircraft? i.e If the control column is held back to maintain a given attitude, does moving the stab remove the aerodynamic force, or does the control column then have to be released back to the neutral position once the aircraft is in trim???*

A: When aircraft in trim (forces of elevator eliminated) yoke back to neutral position.

regards

[Mad (Flt) Scientist]

*e.g. If the control column is left in the neutral position, but the stab is moved up or down. Will the elevator remain flush with the stabilizer or will it remain flush with the longitudinal axis of the aircraft???*

A: Elevator remains flush with stabilizer.

This actually depends on the aircraft. On some aircraft the elevator position is geared to the stab, so if NO column movement is made the elevator moves proportional to the stab movement. Column movement then moves the elevator relative to the geared position.

This would be done if, for example, the stab alone were not powerful enough as a trimming surface.

Most aircraft take the simpler approach described, though.

[catchup]

o.K.

Limit my posting to B727, A300, A320/340;)

regards

[TotalBeginner]

Must confess I'm still confused as to how these trim changes will feel on the controls.

For example, if you were flying a C152 straight and level and in trim, and you rotated the trim wheel towards the nose down position, the yoke would move in the same direction. (unless you applied some back pressure)

Does the same thing happen in a 737 for example, or is the neutral position of the control column always at the same point??

[catchup]

@TotalBeginner

Neutral postion is always same point.

Mad (Flt) Scientist is absoluly right AND I have to correct myself a little concerning B727. It's long ago (17 years or so) but I think at the very end of stabilizer nose down postion (aircraft nose up) the elevator and therefore the yoke goes with the stabilizer a bit. But you would never reach that trim position in normal ops.

regards