13.7 Flight controls (ATA 27/67) — actuation, protection and fly-by-wire

Scope

Part of the B2L Autoflight rating exam (with 13.3) and B2.

• 13.7(a) primary and secondary controls (ATA 27): aileron, elevator, rudder, spoiler; trim tabs; high-lift devices; manual operation; gust locks; artificial feel, yaw damper, Mach trim, rudder limiter; stall warning — level 2.
• 13.7(b) actuation and protection: active load control; lift dump and speed brakes; hydraulic and pneumatic systems; stall protection — level 2.
• 13.7(c) system operation: electrical, fly-by-wire — level 3.
• 13.7(d) rotorcraft controls (ATA 67): cyclic, collective, swashplate, yaw control — level 2.

Primary and secondary controls

Primary	Secondary
Ailerons (roll), elevator/stabilator (pitch), rudder (yaw), roll spoilers	Trim (tabs, trimmable stabiliser), flaps, slats, speed brakes, ground spoilers/lift dumpers

Manual systems use cables, pulleys, bellcranks, push-pull rods and torque tubes. Cable tension is set with a tensiometer and depends on temperature (aluminium structure expands more than steel cable); large aircraft use cable tension regulators. Rigging uses rig pins at neutral positions and travel boards/protractors for surface throws.

Gust locks

Prevent wind damage to surfaces on the ground. Types: external clamps/battens (with red streamers), internal mechanical locks engaged from the flight deck (often interlocked with the throttles so take-off power cannot be set with locks engaged), and hydraulic gust damping — powered surfaces are held by trapped fluid in the actuators when hydraulics are off.