Flight Controls and Landing Gear
Flight Controls and Landing Gear tests control-surface actuation, fly-by-wire redundancy, and landing-gear and brake operation. Questions often combine hydraulic force, rigging, and unsafe-gear logic.
Controls
Primary controls are aileron, elevator and rudder; secondary are flaps, slats, spoilers and trim. Fly-by-wire replaces mechanical cables with computers and actuators; fail-passive leaves a residual mechanical path, fail-operational continues after a failure. Trim reduces steady stick force; feel units and artificial feel simulate aerodynamic loads.
Landing gear
An oleo strut uses gas for spring and oil through an orifice for damping. Torque links keep the wheel aligned; shimmy dampers suppress nose-wheel oscillation. WOW switches inhibit retraction and enable antiskid and autobrake. Antiskid modulates brake pressure; autobrake selects a deceleration level.
Worked example
A control surface actuator has area 20 cm² at 15 MPa, giving F = 15,000,000 × 0.002 = 30,000 N. With a 0.4 m moment arm, torque = 12,000 N·m. If two actuators share the load, each supplies 6,000 N·m; if one is isolated, the remaining actuator must be rated for the full limit load or the surface travel is restricted.
Traps
Confusing gear downlock with hydraulic pressure; a gear can be down but not locked. Do not assume antiskid increases braking on a dry runway; it releases pressure to prevent skid. Flap asymmetry protection and slat/flap disagree alerts are not the same.