Airframe Mechanic Certification Flight Control Systems 5 — Questions and Answers
Question 1: What is the primary cause of aileron flutter on an aircraft?
- Excessive cable tension causing surface stiffness
- Mass imbalance of the control surface about its hinge line (Correct answer)
- Differential cable tensions between left and right ailerons
- Improper rigging of the trim tab
Correct answer: Mass imbalance of the control surface about its hinge line
Flutter occurs when the control surface's center of mass is aft of the hinge line, creating a self-exciting oscillation driven by aerodynamic forces.
Question 2: Which regulation requires that flight control systems be checked for freedom of movement and correct travel before the first flight after certain maintenance actions?
- 14 CFR 91.409
- 14 CFR 43.13 (Correct answer)
- 14 CFR 91.7
- 14 CFR 43 Appendix D
Correct answer: 14 CFR 43.13
14 CFR 43.13 requires mechanics to perform maintenance using methods and data that ensure the work results in at least equal airworthiness, including control system checks.
Question 3: A ground-adjustable tab differs from a trim tab in that it:
- Can be adjusted in flight by the pilot using a cockpit control
- Is adjusted only on the ground and cannot be moved in flight (Correct answer)
- Is driven by a separate hydraulic actuator
- Moves opposite to the main control surface to reduce hinge moment
Correct answer: Is adjusted only on the ground and cannot be moved in flight
Ground-adjustable tabs are bent to a fixed position by maintenance personnel before flight and cannot be repositioned by the pilot from the cockpit.
Question 4: What type of control system uses control signals transmitted electrically to actuators, with no mechanical linkage between cockpit controls and surfaces?
- Hydromechanical
- Power-boosted
- Fly-by-wire (Correct answer)
- Manual reversion
Correct answer: Fly-by-wire
Fly-by-wire (FBW) systems replace mechanical cables and pushrods with electrical signals sent to flight control computers, which then command hydraulic or electromechanical actuators.
Question 5: When checking a flight control system for correct cable routing, a mechanic discovers a cable routed through a fairlead at an angle greater than 3 degrees. This is:
- Acceptable if the cable is at the proper tension
- Unacceptable and the routing must be corrected (Correct answer)
- Acceptable for cables larger than 1/8-inch diameter
- Acceptable only on secondary control systems
Correct answer: Unacceptable and the routing must be corrected
AC 43.13-1B specifies that cables should not pass through a fairlead at an angle greater than 3 degrees, as greater angles cause accelerated wear.
Question 6: What is the purpose of a downspring in a pitch control system?
- To increase elevator authority at high airspeed
- To provide a nose-down force that must be overcome to raise the nose, improving pitch stability feel (Correct answer)
- To prevent the elevator from reaching its maximum up-travel stop
- To return the elevator to neutral when the pilot releases the controls
Correct answer: To provide a nose-down force that must be overcome to raise the nose, improving pitch stability feel
A downspring applies a constant nose-down load to the elevator system, ensuring that increasing back-pressure is required to raise the nose, giving the pilot a more stable pitch feel.
Question 7: What documentation must a technician complete after performing a flight control rigging inspection and adjustment?
- Only an entry in the aircraft logbook if hardware was replaced
- A maintenance record entry in the aircraft records per 14 CFR 43.9 describing the work, date, and signature (Correct answer)
- A Form 337 filed with the FAA within 48 hours
- A logbook entry is only required if the aircraft is returned to service after annual inspection
Correct answer: A maintenance record entry in the aircraft records per 14 CFR 43.9 describing the work, date, and signature
14 CFR 43.9 requires a maintenance record entry for all maintenance, preventive maintenance, rebuilding, or alteration, including rigging adjustments, with date, description, and approval signature.
Airframe Mechanic Certification Flight Control Systems 5
What is the primary cause of aileron flutter on an aircraft?