Airframe Mechanic Certification Ice and Rain Control Systems 5 — Questions and Answers
Question 1: What is the purpose of the 'hold-down' (suction) function in a pneumatic deicing boot system?
- To create aerodynamic suction that pulls ice toward the boot for collection
- To keep the boot deflated and conformed to the leading edge when not inflating (Correct answer)
- To hold accumulated ice in place until the pilot selects a shed cycle
- To increase system pressure during the inflation stroke
Correct answer: To keep the boot deflated and conformed to the leading edge when not inflating
Suction is applied to the boot between inflation cycles to hold it tightly against the leading edge skin, minimizing aerodynamic drag and preventing flutter.
Question 2: An aircraft's windshield wiper system fails to return to the park position after shutdown. The MOST likely cause is a fault in which component?
- The wiper blade squeegee material
- The park switch or wiper motor parking circuit (Correct answer)
- The windshield heating control unit
- The cockpit wiper speed selector switch
Correct answer: The park switch or wiper motor parking circuit
The wiper motor parking circuit, controlled by an internal or external park switch, is responsible for driving the wiper to its park position at shutdown.
Question 3: What is the purpose of the 'ice bridging' concern associated with deicing boots?
- Electrical arcing that bridges boot heating elements, causing a short circuit
- Ice that forms an arch over an inflated boot so it cannot be shed when deflated (Correct answer)
- A metallic bridge bonding the boot to the wing spar for electrical continuity
- Bridging insulation tape used to repair small boot cuts
Correct answer: Ice that forms an arch over an inflated boot so it cannot be shed when deflated
If boots are activated before sufficient ice accumulates, the ice can arch (bridge) over the inflating tube and remain adhered to the wing when the boot deflates.
Question 4: Which system component monitors for electrical faults in a windshield heating system and protects against overtemperature?
- The aircraft master caution annunciator only
- An automatic temperature controller with overtemperature cutout (Correct answer)
- The windshield wiper speed control module
- The bleed air shutoff valve position indicator
Correct answer: An automatic temperature controller with overtemperature cutout
Windshield heating controllers monitor glass temperature using embedded sensors and automatically shut off power if overtemperature is detected to prevent delamination.
Question 5: Frost on an aircraft wing before takeoff is hazardous primarily because it:
- Adds significant weight that shifts the center of gravity aft
- Disrupts the smooth airflow over the wing and reduces lift (Correct answer)
- Blocks fuel vent holes causing fuel system pressure problems
- Freezes the aileron hinges and prevents control surface movement
Correct answer: Disrupts the smooth airflow over the wing and reduces lift
Even a thin layer of frost roughens the wing surface enough to disrupt the boundary layer airflow, reducing lift and increasing stall speed.
Question 6: During a TKS weeping wing system inspection, the mechanic notices some porous titanium panel holes are clogged. What is the correct maintenance action?
- Drill out the clogged holes to restore flow
- Replace the clogged porous panel per the AMM (Correct answer)
- Flush the system with water at high pressure to clear blockages
- Apply solvent to dissolve mineral deposits, then reinstall
Correct answer: Replace the clogged porous panel per the AMM
Clogged TKS panels must be replaced rather than drilled or otherwise modified, as pore size and distribution are precisely controlled for correct fluid flow.
Question 7: What is the significance of Appendix C versus Appendix O in FAR Part 25 for ice protection system certification?
- Appendix C covers structural loads; Appendix O covers electrical system failures
- Appendix C defines the traditional icing envelope; Appendix O defines the SLD icing envelope (Correct answer)
- Appendix C applies to jets; Appendix O applies to turboprops only
- Appendix C is for anti-ice systems; Appendix O is for deice systems only
Correct answer: Appendix C defines the traditional icing envelope; Appendix O defines the SLD icing envelope
Appendix C defines the classical continuous maximum and intermittent maximum icing envelopes, while Appendix O (added later) defines the SLD (freezing rain and freezing drizzle) icing envelope.
Airframe Mechanic Certification Ice and Rain Control Systems 5
What is the purpose of the 'hold-down' (suction) function in a pneumatic deicing boot system?