Moving fin?

[chornedsnorkack]

Many planes have a fixed tailplane and moving elevator, usually at trailing end of tailplane.

However, some planes move the whole tailplane and call it stabilator.

Many planes have a fixed fin and moving rudder at the trailing edge of fin.

Which planes move the whole fin? And what is it called? Stabiludder?

[Rainboe]

With horizontal stabilators, the structure passes through the fuselage and is structurally easier to support. A moving fin would just be a pivot with the flight control above it. It would take a lot of fuselage strengthening to prevent deformation and to support a whole moving fin, for a structure that would not get a great deal of use. A rudder on the end of the fin does a satisfactory job- a whole moving 'finilator' would be far heavier, and still end up weaker. I know of no aeroplane at all that uses this solution.

[chornedsnorkack]

Originally Posted by Rainboe

With horizontal stabilators, the structure passes through the fuselage and is structurally easier to support. A moving fin would just be a pivot with the flight control above it. It would take a lot of fuselage strengthening to prevent deformation and to support a whole moving fin, for a structure that would not get a great deal of use. A rudder on the end of the fin does a satisfactory job- a whole moving 'finilator' would be far heavier, and still end up weaker. I know of no aeroplane at all that uses this solution.

Well, one advantage of a stabilator over elevators in the rear end of a fixed tailplane is alleged to be that shocks might limit elevator effectiveness, whereas moving the whole tailplane up to leading edge is alleged to be better.

But the same reasoning might apply to fin and rudder... when does a rudder have enough authority to compensate for a violent unstart of an outboard engine...

[the dean]

Originally Posted by chornedsnorkack

Which planes move the whole fin? And what is it called? Stabiludder?

am i incorrect or did'nt/does'nt the mooney have a fin that is capable of foreward and backward movement...( if so ) presumably for slow/fast flight.

never driven one but i think i am correct.

sure mooney drivers will verify...

the dean.

[BOAC]

Quite a few, actually!

http://forum.keypublishing.co.uk/sho...stpost&t=65519

[Rainboe]

Well I didn't know the Blackjack had an all moving part fin section. However, leaving aside light aeroplanes, fighters and Soviet experimental aeroplanes, I cannot see it as a solution that is worth the problems involved. It is not a solution that even the latest large Russian airliners have tried. I cannot imagine airliners finding such systems worth the expense of engineering and strengthening needed for a questionable benefit. The base of a 747 fin is 48 inches/123 cms wide- can you imagine the stronger fin required and the pivot system to support that enormous size and weight, as well as the fuselage strengthening to support the pivot without flexing? Any drag reduction saving will be minimal as it will only come into use in an engine-out scenario as opposed to an all-moving stabilator being used throughout every flight.

[BOAC]

So.............. to answer the poster's question

Yes, some, including some well known military a/c, have had it. I don't think it has a specific name as such.

Its advantage would be the reduction in drag (at all stages of flight) due to the need for a smaller fin. I doubt it would be efficient though as it would require a stroger (=heavier) structure. Rockets use moveable fins to steer.

[stevef]

I believe The Dean is right; the Mooney fin/tailplane moves via the trim wheel. You can almost pluck a note on the aerial wire between the top of the fuselage and tip of the fin when the trim's fully one way.

[Rainboe]

The question was all about moving fins as opposed to fixed fin/rudder. The mooney tail does move- it pitches up and down, but the fin does not twist- it just goes with the structure. Great. But nothing to do with this question.

[stevef]

True! Merely a passing comment.