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View Full Version : Degrees of movement of spoiler panels on take off.


A37575
20th Jun 2006, 04:43
On previous posts there has been intensive discussion on spoiler drag with excessive control wheel deflection on a cross wind take off. From anecdotes heard, excessive pilot control wheel input in crosswind take offs may be much more common than realised. It seems to largely stem from habits ingrained in ab-initio flight training and carried over. On the other hand perhaps the argument is trivial as aircraft are not going off the end of runways due unforeseen insidious drag.

Has anyone any specific figures on the amount of spoiler panel movement in degrees for say half wheel movement during a take off? As speed increases down the runway with constant wheel angle, do the spoilers change angle in any way - blowing down the faster the aircraft goes and so on?

Mad (Flt) Scientist
20th Jun 2006, 13:08
Has anyone any specific figures on the amount of spoiler panel movement in degrees for say half wheel movement during a take off? As speed increases down the runway with constant wheel angle, do the spoilers change angle in any way - blowing down the faster the aircraft goes and so on?

The spoileron-wheel gearing is going to be different according to the type of aircraft, but I'd be astonished if any aircraft has hinge-moment limiting on its spoilers at typical takeoff speeds.

Michael1282
20th Jun 2006, 22:02
Yes i would agree.
Spoiler deflection cannot be related to IAS or something like that.
It starts at a specific point of control wheel displacement and is proportional to this.

In my opinion during some x-wind conditions you have to give much aileron input (with spoiler rise) to keep the wings level during rotation. No matter if it causes too much drag, according to the FCTM. (Still better than a wing tip touching the grass :ouch: )

Mad (Flt) Scientist
20th Jun 2006, 22:43
Spoiler deflection cannot be related to IAS or something like that.
It starts at a specific point of control wheel displacement and is proportional to this.)

Well, just for completeness....

there WILL be some speed above which the hinge moment on the spoilers will overcome the capability of the actuation; whether that speed is operationally significant or not is type-dependent, but I'd expect that you'd start seeing effects at about Vmo. (below that, you typically want to have the spoilers available; less need above, so Vmo as a design speed wouldn't be a bad first guess)

Also, it is conceivable that one might vary the wheel-spoiler schedule with speed (perhaps Mach, most likely) to reflect changes in control effectiveness. (Though off the top of my head I don't *think* we do so)

78deg
21st Jun 2006, 17:48
I do not have the manual in front of me, but from memory.
B757
0deg to 11deg control wheel no spoilers
11deg to 55deg control wheel, spoiler on the down going wing deploys as an inboard aileron.

On swept wing jets it is very important to have into wind aileron on take off and upto 55 deg control wheel will not increase drag.

With experience the amount of deflection required can be jugded by the amount of rudder required to keep straight.

At lift off all is revealed and then roll must be corrected if nessesary.

Rainboe
21st Jun 2006, 19:33
A37575, a word you use implies you have picked up the wrong end of the stick in the thread you refer to:
On previous posts there has been intensive discussion on spoiler drag with excessive control wheel deflection on a cross wind take off.
Can you guess which one it is?

Now why do you think the discussion was about excessive use of control wheel displacement leading to spoiler displacement? The discussion was actually about using the recommended amount of control wheel into wind to prevent wing lift as opposed to using none until the wing actually lifts and then using control wheel displacement to lower it again. It therefore makes your comment read differently
It seems to largely stem from habits ingrained in ab-initio flight training and carried over.
.....habits as supported by current training practices and instruction to apply the correct recommended amount of control wheel displacement for a crosswind. If people are applying excessive control, then they must be stopped immediately!