Actuation systems for control surfaces for aircraft

An actuation system for a control surface for an aircraft in which the aircraft comprises a wing or stabilizer to which a control surface is hinged, the wing or stabilizer comprises a sub-structure, and the control surface has a trailing edge, the actuation system comprising:

• first, second, third and fourth actuators;
• first and second bell cranks, wherein each of the first and second bell cranks comprises:
• a first and a second crank arm, wherein:
• the first and second crank arms intersect with and are joined to each other at an intersection;
• the first and second crank arms extend from the intersection at an angle to each other, the first bell crank is pivotally connected to the sub-structure by a first pivot extending through the first bell crank's intersection;
• and
• the second bell crank is pivotally connected to the sub-structure by a second pivot extending through the second bell crank's intersection;
• and
• at least one push pull rod system;
• wherein:
• the first and third actuators have first and second ends;
• the first ends of the first and third actuators are connected to the sub-structure;
• the second end of the first actuator is connected to the first crank arm of the first bell crank at a first connection position;
• the second end of the third actuator is connected to the first crank arm of the first bell crank at a third connection position;
• the second and fourth actuators have first and second ends;
• the first ends of the second and fourth actuators are connected to the sub-structure;
• the second end of the second actuator is connected to the first crank arm of the second bell crank at a second connection position;
• the second end of the fourth actuator is connected to the first crank arm of the second bell crank at a fourth connection position;
• and
• in the first bell crank a distance (D1) between the first connection position and the first pivot is greater than a distance (D3) between the third connection position and the first pivot, and in the second bell crank a distance (D2) between the second connection position and the second pivot is greater than a distance (D4) between the fourth connection position and the second pivot.