You´ve got to distinguish between the flight spoilers, which are either controled by a control wheel input through a spoiler mixer and assist the ailerons (coming up on the downwing side during a turn in direct ratio to the control wheel deflection), the speed brakes (controled by the speed brake handle, come up during flight symetrically, often the same surfaces as the flight spoilers, just a different control input. Actually, the control wheel input and the speedbrake input are often overlaid. E.g. I´ve got the speedbrakes out at maximum flight deflection, now I´m turning my control wheel, the upper wing spoilers will actualy retract). The amount of deflection is usualy limited in flight. Taking the
MD-11 as an example, the maximum deflection for lateral control (spoilers to assist ailerons is 60° assymmetricaly, as speedbrake 30° symmetricaly and as ground spoiler (to kill the residue lift on landing) 60° symmetricaly. The extension of the speedbrakes is inhibited mechanically if the flaps are extended (I´ve heard from pilots that you can, theoreticaly, deploy the speedbrakes first and then the flaps, but the plane would turn into a brick). There is also a mechanically interlock from the nose gear ground shift mechanism, which prevents full symmetrical deployment of the spoilers if the nose gear strut isn´t compressed (means you can´t pull the speedbrrake lever into the ground spoiler / 60° position unless the nose gear is on the ground. For automatic ground spoiler deployment there exists an electric actuator under the center pedestal, which, if the spoilers are armed by pulling the handle up out of the "down" detent, will move the speedbrake lever back on landing (or a rejected take-off), to 30° on landing the moment there isd a wheel speed input from the rear wheels of the MLG boogies and to 60° once the nose wheel touches the ground.
There is no space in here now to get into the details of the groundspoiler control logic, just to tell you, it gets inputs from the FADECs, flap position transmitter, wheel speed sensors, ground sensing relays and the radio altimeters.
Jan
