Airframe Mechanic Aircraft Assembly and Rigging Questions and Answers — Questions and Answers
Question 1: After replacing a flight control cable, a technician must adjust its tension. Why is it critical to consider the ambient temperature when using a tensiometer?
- To prevent corrosion of the turnbuckle threads.
- The airframe and cable have different coefficients of thermal expansion. (Correct answer)
- High temperatures can damage the internal components of the tensiometer.
- The cable's breaking strength is significantly reduced at lower temperatures.
Correct answer: The airframe and cable have different coefficients of thermal expansion.
Aircraft fuselages, typically made of aluminum alloy, expand and contract at a different rate than steel control cables when the temperature changes. Aircraft maintenance manuals provide temperature-tension charts to ensure the cable is tensioned correctly for a standard temperature (usually 70°F), regardless of the ambient temperature during adjustment. This ensures proper control feel and prevents flutter without overstressing the system at temperature extremes.
Question 2: A technician is performing a static balance check on an aileron that has just been repainted. The procedure involves supporting the aileron on a knife-edge fixture at its hinge line. Which of the following conditions indicates the aileron is properly balanced?
- The trailing edge consistently rises to a 15-degree angle.
- The leading edge slowly drops until it rests on the fixture.
- The aileron remains in a horizontal position or exhibits a slight nose-down tendency. (Correct answer)
- The aileron oscillates for several seconds before settling with the trailing edge down.
Correct answer: The aileron remains in a horizontal position or exhibits a slight nose-down tendency.
Proper static balance requires the control surface's center of gravity (CG) to be at or slightly ahead of the hinge line. When placed on a knife-edge at the hinge line, a balanced surface will remain horizontal or show a slight tendency to be nose-down. A trailing-edge-heavy condition (underbalance) is undesirable as it can lead to control surface flutter at high speeds.
Question 3: Which of the following is the primary purpose of incorporating dihedral in an aircraft's wing design?
- To increase the wing's overall lift coefficient at high angles of attack.
- To improve longitudinal stability around the pitch axis.
- To enhance lateral stability around the roll axis. (Correct answer)
- To decrease parasitic drag during high-speed cruise flight.
Correct answer: To enhance lateral stability around the roll axis.
Dihedral is the upward angle of the wings from the horizontal. Its primary purpose is to provide positive lateral stability (stability in roll). When an aircraft with dihedral is disturbed and one wing drops, a sideslip occurs. This sideslip causes the lower wing to experience a greater angle of attack and generate more lift, creating a rolling moment that tends to restore the aircraft to a wings-level attitude.
Question 4: When safety wiring a turnbuckle using the double-wrap method, what is the generally accepted rule regarding the number of threads that may be exposed at either end of the barrel?
- No more than five threads.
- Exactly four threads for maximum grip.
- No more than three threads. (Correct answer)
- At least five threads must be visible for inspection.
Correct answer: No more than three threads.
To ensure adequate thread engagement and structural integrity, standard aviation practice dictates that no more than three threads of the turnbuckle terminal should be exposed outside the barrel after tensioning and before safetying. This ensures the connection is strong enough to handle its rated load.
Question 5: A post-maintenance flight test reveals an aircraft has a persistent tendency to roll to the left. Before resorting to trimming devices, the mechanic should perform which of the following rigging checks?
- A cable tension check of the rudder system.
- A symmetry and incidence check of the wings. (Correct answer)
- An operational check of the horizontal stabilizer travel.
- A static balance check of the elevator.
Correct answer: A symmetry and incidence check of the wings.
A tendency to roll indicates an asymmetry in the lift being produced by the wings. This can be caused by improper wing rigging, where one wing has a slightly different angle of incidence (the angle at which the wing is attached to the fuselage) or if the wings are not symmetrical with respect to the aircraft's longitudinal axis. A symmetry and incidence check is required to verify and correct these angles.
Question 6: What is the primary function of a turnbuckle in an aircraft flight control cable system?
- To act as a fusible link that fails under excessive loads.
- To allow for the adjustment of cable length and tension. (Correct answer)
- To provide a quick-disconnect point for cable removal.
- To dampen vibrations transmitted along the control cable.
Correct answer: To allow for the adjustment of cable length and tension.
A turnbuckle is a device consisting of a barrel with internal screw threads at both ends (one right-hand and one left-hand) that connects to threaded cable terminals. By rotating the barrel, the terminals are drawn together or pushed apart, allowing for precise adjustments to the length and, therefore, the tension of the control cable.
Airframe Mechanic Aircraft Assembly and Rigging Questions and Answers
After replacing a flight control cable, a technician must adjust its tension.
Why is it critical to consider the ambient temperature when using a tensiometer?