Airframe Mechanic Certification Flight Control Systems 2 — Questions and Answers
Question 1: What is the primary purpose of a trim tab on a control surface?
- To increase control surface deflection range
- To relieve the pilot of sustained control forces (Correct answer)
- To limit maximum control surface travel
- To provide aerodynamic balance for the surface
Correct answer: To relieve the pilot of sustained control forces
Trim tabs are adjusted to relieve the pilot of continuous pressure needed to maintain a desired flight attitude.
Question 2: Which type of cable rigging check verifies that control surfaces move in the correct direction when cockpit controls are deflected?
- Tension check
- Continuity check
- Travel check
- Operational check (Correct answer)
Correct answer: Operational check
An operational check confirms correct direction of surface movement relative to cockpit control input, ensuring no crossed cables.
Question 3: A differential aileron system is designed to move the upgoing aileron:
- More than the downgoing aileron (Correct answer)
- The same amount as the downgoing aileron
- Less than the downgoing aileron
- Only when the flaps are extended
Correct answer: More than the downgoing aileron
Differential ailerons reduce adverse yaw by raising the upgoing aileron a greater amount than the downgoing aileron is lowered.
Question 4: What does a 'hard over' failure in a fly-by-wire flight control actuator mean?
- The actuator moves to its neutral position and stops
- The actuator drives the control surface to its maximum deflection and holds (Correct answer)
- The actuator loses hydraulic pressure and goes limp
- The actuator oscillates rapidly between full deflections
Correct answer: The actuator drives the control surface to its maximum deflection and holds
A hard-over failure causes the actuator to drive the surface to its physical stop and remain there, a potentially catastrophic condition.
Question 5: On a Cessna-style single-engine aircraft, the elevator control system uses which type of cable routing at the empennage?
- Push-pull tubes only
- Cables routed over pulleys to a bellcrank (Correct answer)
- Torque tubes connected directly to the elevator
- Hydraulic lines to actuators
Correct answer: Cables routed over pulleys to a bellcrank
Most light aircraft route elevator cables aft over a series of pulleys and fairleads to a bellcrank that converts cable motion to surface movement.
Question 6: What is the correct method for checking flight control cable tension on an aircraft?
- Visual inspection of cable sag
- Using a calibrated tensiometer at the specified temperature (Correct answer)
- Plucking the cable and listening for a specific tone
- Checking the turnbuckle thread exposure only
Correct answer: Using a calibrated tensiometer at the specified temperature
A calibrated tensiometer provides an accurate reading that can be compared against the manufacturer's temperature-corrected tension table.
Question 7: Which component prevents a flight control cable from jumping off a pulley during slack conditions?
- Swaged terminal
- Cable guard or guard pin (Correct answer)
- Fairlead bracket
- Turnbuckle barrel
Correct answer: Cable guard or guard pin
Cable guards (guard pins or keeper plates) retain the cable on the pulley groove if tension momentarily goes slack.
