Few questions regarding the horizontal stabilizer

[z.khalid]

May sound stupid but just a little confused with this concept.
Main job of the stabalizer is stability.
To allow a pilot to trim and remove the force off his hands, also to use on takeoff usually airliners set the stabalizer forward or aft depending on forward or aft CG.

I'm curious that in what direction will the stabalizer move?
For example on a climb, the elevator is deflected upwards, will the stabalizer also deflect upwards or?
In cruise?
Looking for the logic behind this.

And finally. What happens if while in cruise the stabalizer gets jammed?

Thanks in advance:ok:

[packo1848]

My understanding is that if the elevator is deflected upwards, to trim this the stabiliser will reduce angle of attack (leading edge down), it essentially moves to bring itself into line with the elevator.

The logic: reduced angle of attack means less lift, therefore the nose pitches up.

I haven't got a clue what happens if it sticks in cruise, though i was told once that on the old 737 classics (talking 100/200 series) the pilots could overcome the forces required to pitch the a/c by sticking their feet on the dash and pulling hard!

[Turbavykas]

I don't think I fully understand your questions but trim remove force on the controls so if we have situation like ____/ the trim should move it down as the final result to be _____ as then there will be no force on the controls

[Lightning Mate]

What happens if while in cruise the stabalizer gets jammed?

You lose trim.

The trick would be to maintain the IAS at which it jammed for as long as possible and ensure passengers and crew remain seated to minimise CG movement.

You may well be limited in the amount of flap which may be used because of the pitching moment caused.



the pilots could overcome the forces required to pitch the a/c by sticking
their feet on the dash and pulling hard!


But the elevators are still working.

[Lightning Mate]

http://i636.photobucket.com/albums/uu82/Lightning_29/varinctailplaneConverted_zps97d7fe9e.jpg

[RemoveB4Flght]

You are confusing elevator trim a bit with stabilizer trim.

On a conventional airplane, the trim tab or servo tab is used to relieve the amount of pressure on the yoke by acting as a "mini elevator" that moves in the opposite direction to "fly" the elevator in the desired direction.

Some models have an anti-servo tab, which moves in the same direction as the elevator. This creates an aerodynamic force that works against the elevator, and the reason for this is to prevent or discourage over controlling the plane by pitching too much too quickly.

On large jet aircraft, any reduction in drag results in fuel savings which means money saved. The angle of incidence or deck angle of the jet changes in flight according to speed or weight. This means if the stabilizer was fixed, it could require an elevator deflection to compensate. A trimmable stabilizer can remain neutral and this is much more efficient.

If the trimmable stabilizer jams in flight, depending on the position it was stuck in would result in anything from increased fuel consumption to a more difficult to control aircraft.

[Lord Spandex Masher]

to trim this the stabiliser will reduce angle of attack (leading edge down)

Leading edge down is increasing the stabiliser AoA, or more accurately angle of incidence, which is what you've done by moving the elevator up and now you're just trimming out stick force.

reduced angle of attack means less lift, therefore the nose pitches up.

The nose will pitch down, assuming constant IAS.

[Lightning Mate]

You are confusing elevator trim a bit with stabilizer trim.

I'm not confused about anything old chap. I was merely trying to help the OP with his original question.