|The spoilers used on the A320 are divided into two main activities. For roll control; the roll spoilers are the most significant surface controls used. The spoilers are also used for decelerating the aircraft during flight and during landing using the speed brakes.
Roll control is provided on each wing by one aileron, augmented by four roll spoilers mounted on the upper wing surfaces. Surface controls are actuated by independently supplied, electrically signalled, hydraulic servojacks. The position of the roll spoilers is based on signals from the sidestick controllers processed by the electrical FCC or by the automatic pilot. If the sidestick is moved it generates a signal towards the SEC, and to one of the ELACs. Then the SEC passes the signal through to one of the servojacks which makes sure the spoilers are in the right position.
During the flight the two outer spoilers can be used in combination with the aileron to compensate vertical acceleration due to gusts. This Load Alleviation Function (LAF) is accomplished by the electrical flight control system. The LAF is implemented in the ELAC and SEC. There are four specific accelerometers that are installed to provide the flight computers with vertical acceleration values. These sense the up gust and deploy the spoilers to smooth out the normal result of an up gust of wind.
There are three speed brakes located on the upper surface of each wing. Each speed brake group is operated by one servojack controlled by the corresponding electrical flight computer, which is also used for the roll spoilers. All of the five spoilers mounted on each wing of the A320 are used as ground spoilers during landing. They are automatically extended after touchdown when specific ground conditions are fulfilled.
|Ground Spoilers and Speed Brakes
Conditions such as the selection of one engine thrust reverser or the speed brake lever being armed to the deploy position (figure 1.3).
When the autopilot is in command, this means the FMGS is maintaining pitch control. It sends electrical signals to both ELAC’s which produce an output activating the elevator actuators. Each elevator is powered by two hydraulic actuators, one in active mode while the other serves as back-up. Both actuators become active in case of large pitch demands.