Free Airframe Mechanic Assembly and Rigging Questions and Answers — Questions and Answers
Question 1: A technician is inspecting a properly tensioned turnbuckle in a primary flight control system and observes four threads are exposed between the barrel and the cable end fitting. What is the correct course of action?
- This is acceptable as long as the safety wire can be installed correctly.
- Replace the turnbuckle with one of a more appropriate length. (Correct answer)
- Tighten the turnbuckle until no threads are exposed to maximize engagement.
- Document the finding and re-inspect at the next 100-hour inspection.
Correct answer: Replace the turnbuckle with one of a more appropriate length.
According to standard aircraft maintenance practices (such as those in AC 43.13-1B), no more than three threads should be exposed on either end of a turnbuckle barrel. Exposing four or more threads indicates insufficient thread engagement, which compromises the strength of the connection. The correct action is to use a turnbuckle of the proper length to achieve the correct cable tension while ensuring adequate thread engagement.
Question 2: What is the primary reason that aircraft maintenance manuals provide a temperature/tension chart for rigging flight control cables?
- To ensure the tensiometer is properly calibrated before use.
- To prevent corrosion from forming between the cable strands.
- To compensate for the different thermal expansion rates of the aluminum airframe and the steel cables. (Correct answer)
- To determine the correct size of safety wire to use on the turnbuckles.
Correct answer: To compensate for the different thermal expansion rates of the aluminum airframe and the steel cables.
Aircraft structures, typically made of aluminum alloys, expand and contract at a different rate than the steel control cables when subjected to temperature changes. A temperature/tension chart allows a technician to set the correct cable tension at a given ambient temperature, ensuring that the tension will remain within the specified limits whether the aircraft is on a hot ramp or at high altitude where temperatures are very low.
Question 3: After an aileron has been repainted, it must be rebalanced. Which of the following is the most critical reason for this procedure?
- To ensure the new paint is properly cured and bonded to the surface.
- To verify the correct range of motion for the control surface.
- To prevent the onset of high-frequency control surface flutter. (Correct answer)
- To reduce the amount of force the pilot must exert on the controls.
Correct answer: To prevent the onset of high-frequency control surface flutter.
Adding paint adds weight to the control surface. If this weight is not distributed correctly relative to the hinge line, it can change the surface's center of gravity. An improperly balanced control surface is highly susceptible to flutter, a rapid and destructive oscillation caused by the interaction of aerodynamic, inertial, and elastic forces, which can lead to catastrophic structural failure.
Question 4: Before checking the wing dihedral and incidence angles during a rigging check, what is the most critical preparatory step?
- Leveling the aircraft both longitudinally and laterally according to the maintenance manual. (Correct answer)
- Ensuring the fuel tanks are completely full to establish a baseline weight.
- Setting all flight controls and trim tabs to their neutral positions.
- Retracting the landing gear and placing the aircraft on tail stands.
Correct answer: Leveling the aircraft both longitudinally and laterally according to the maintenance manual.
All airframe alignment and rigging measurements must be taken from a specific, known reference plane. The aircraft must first be leveled according to the manufacturer's specific instructions and leveling points (often using a spirit level or plumb bob). Performing these checks on an un-level aircraft will result in inaccurate measurements and improper rigging.
Question 5: During an inspection of a control cable passing over a pulley, a single broken wire is discovered. According to FAA AC 43.13-1B, what action is required?
- The entire control cable assembly must be replaced. (Correct answer)
- The cable may remain in service if no more than three wires are broken.
- Apply an approved lubricant and re-inspect after the next flight.
- Repair the broken wire by wrapping it with safety wire.
Correct answer: The entire control cable assembly must be replaced.
According to FAA guidance in AC 43.13-1B, any cable assembly that has even one broken wire strand located in a critical fatigue area must be replaced. A critical fatigue area includes any section where the cable runs over a pulley, through a fairlead, or within one foot of a swaged fitting.
Question 6: In aircraft assembly and maintenance, what is the primary function of a cotter pin when used with a castellated nut?
- To act as a washer to distribute the clamping force of the nut.
- To provide a visual indication that the correct torque has been applied.
- To allow for quick removal of the nut without tools.
- To act as a positive locking device to prevent the nut from loosening due to vibration. (Correct answer)
Correct answer: To act as a positive locking device to prevent the nut from loosening due to vibration.
A cotter pin is a safetying device used to secure bolts, nuts, and other pins. When used with a castellated nut on a drilled bolt, the pin is passed through the castellations and the hole in the bolt, and its ends are bent. This physically prevents the nut from rotating and loosening, which is critical in high-vibration environments like an aircraft.
Free Airframe Mechanic Assembly and Rigging Questions and Answers
A technician is inspecting a properly tensioned turnbuckle in a primary flight control system and observes four threads are exposed between the barrel and the cable end fitting.
What is the correct course of action?