Ice and Rain Control Oral Exam Questions and Answers
Practice explaining how ice protection and rain removal work before discussing a check or a fault. These questions follow Airframe subject AM.II.L, Ice and Rain Control Systems, with separate prompts for prevention, removal, detection, and maintenance precautions.
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What should my answer explain?
Begin by naming the system and its purpose. Then trace the pressure, heat, or fluid that produces the result. Do not treat every aircraft as having the same controls or operating sequence.
Pair each maintenance answer with the relevant manufacturer's procedure during study. Rehearse the reason for the precaution as well as the action.
FAA-S-ACS-1, p. 40, AM.II.L
Use these prompts alongside the ACS codes on your Airman Knowledge Test Report (AKTR). Rehearse an answer before opening the cited source to check it.
Which ACS elements do these questions practice?
The table identifies the elements used below. It is not a prediction of your assigned questions.
| ACS element | Study focus |
|---|---|
| AM.II.L.K1 | Aircraft icing causes/effects. |
| AM.II.L.K3 | Aircraft and powerplant anti-ice systems and components. |
| AM.II.L.K2 | Ice detection systems. |
| AM.II.L.K4 | De-ice systems and components. |
| AM.II.L.K6 | Anti-icing and de-icing system maintenance. |
| AM.II.L.R1 | System testing or maintenance. |
| AM.II.L.K5 | Wiper blade, chemical, and pneumatic bleed air rain control systems. |
Which oral exam questions can I practice?
These practice questions are built from ACS elements; they are not actual FAA test questions. The short explanations are study answers, not complete aircraft maintenance procedures.
1. Why is aircraft icing a problem beyond the added weight?
ACS: AM.II.L.K1
Ice changes the airfoil shape, increases drag, and reduces lift. Ice can also cause destructive vibration, hamper instrument readings, unbalance or freeze control surfaces, hamper radio reception, and affect engine performance. When chunks of ice break off, they can cause engine failures and structural damage. The aircraft may become harder to control as ice forms unevenly.
FAA-H-8083-31B, Airframe, p. 15-1
2. How do clear ice and rime ice form differently?
ACS: AM.II.L.K1
Clear ice forms when droplets are large, such as in rain or cumuliform clouds: the remaining liquid spreads over the surface and gradually freezes into a smooth sheet. Rime forms when drops are small, such as in stratified clouds or light drizzle, and they freeze rapidly before spreading; trapped air gives it a white appearance. Clear ice is hard, heavy, and tenacious, while rime is brittle and more easily removed.
FAA-H-8083-31B, Airframe, p. 15-1
3. How does anti-icing differ from deicing?
ACS: AM.II.L.K3
Anti-icing equipment is designed to prevent ice from forming and is turned on before entering icing conditions. Deicing equipment is designed to remove ice after it begins to accumulate, typically on wing and stabilizer leading edges.
FAA-H-8083-31B, Airframe, p. 15-3
4. Does an ice detector always switch on the anti-ice system?
ACS: AM.II.L.K2
No. Ice detector sensors can warn the crew with an annunciator light. In some aircraft models, the ice-detection system also automatically turns on the wing anti-icing system when icing is detected.
FAA-H-8083-31B, Airframe, p. 15-3
5. How do pneumatic deicing boots remove ice, and why is vacuum applied afterward?
ACS: AM.II.L.K4
Pneumatic pressure expands the boots and breaks away ice accumulated on them. Vacuum deflates the boots and holds them tightly against the aircraft when they are not in use. On GA systems, the inflation and deflation cycle cracks the ice so the airstream can carry it away. On reciprocating-engine aircraft, the air typically comes from a dedicated engine-driven air pump: its pressure side inflates the boots, and its suction side holds them tight when they are not inflated. Turbine aircraft typically use bleed air from the engine compressor.
FAA-H-8083-31B, Airframe, p. 15-12
6. What should you inspect on a pneumatic deicer boot?
ACS: AM.II.L.K6
During each preflight and scheduled inspection, check the boots for cuts, tears, deterioration, punctures, and security. Periodic inspections also check components and lines for cracks. Keep the boots free of gasoline, oil, grease, dirt, and other deteriorating substances. The airframe or component manufacturer's instructions should be followed.
FAA-H-8083-31B, Airframe, p. 15-21 · FAA-H-8083-31B, Airframe, p. 15-20
7. What limits and indications matter when ground-checking pneumatic deicing with an external air source?
ACS: AM.II.L.R1
Do not exceed the system's established test pressure. Before switching on deicing, watch the vacuum-operated instruments: movement indicates that one or more check valves have failed to close and reverse flow through the instruments is occurring. Correct that problem before continuing. With the system on, the pressure gauge fluctuates as the tubes inflate and deflate, and the vacuum gauge should hold a relatively steady reading, although not all systems use a vacuum gauge. Check the boot inflation sequence against the aircraft maintenance manual.
FAA-H-8083-31B, Airframe, p. 15-20
8. How does a heated-air rain removal system clear the windshield?
ACS: AM.II.L.K5
A pneumatic rain removal system directs a flow of heated air over the windshield. The air breaks rain drops into small particles that are then blown away. The air also heats the windshield to prevent moisture from freezing. An electric blower or bleed air can supply the air.
FAA-H-8083-31B, Airframe, p. 15-28
9. How is heat controlled in an electrically heated windshield?
ACS: AM.II.L.K3
Window heat systems use transformers to supply power and feedback devices, such as thermistors, to give a control unit the information needed to keep temperature within acceptable limits. Some systems are automatic and others use flight-deck switches, and separate circuits for pilot and co-pilot are common to ensure visibility in case of a malfunction. For the details of a particular system, consult the manufacturer's maintenance information.
FAA-H-8083-31B, Airframe, p. 15-29
10. Why should chemical rain repellent not be operated on a dry windshield?
ACS: AM.II.L.K5
On a dry window, heavy, undiluted repellent restricts visibility, so the system should only be used in very wet conditions. Repellent residue from application in dry weather or very light rain can also cause staining or minor corrosion of the aircraft skin, so any concentrated repellent or residue should be removed with a thorough fresh-water rinse at the earliest opportunity.
FAA-H-8083-31B, Airframe, p. 15-27
How do I answer it out loud?
Compare clear and rime ice aloud. Next, describe one pneumatic boot cycle, including why the boot stays flat between cycles. Finish with the dry-windshield rain-repellent question and explain the visibility consequence before describing the response.
How should I check my practice answer?
After speaking, compare your explanation with the answer and the cited FAA page. Check the reason, the conditions, and any limitation stated in the source. Repeat the question without looking until you can give a connected spoken answer.
Use references during study, then close them for the spoken rehearsal. The ACS states that reference material is not allowed for answering oral questions.
What else should I know?
Where on an aircraft is ice typically controlled?
Typical locations are the wing leading edges, the vertical and horizontal stabilizer leading edges, windshields and windows, heater and engine air inlets, pitot and static air data sensors, propeller blade leading edges and spinners, carburetors, and lavatory drains and potable water lines.
FAA-H-8083-31B, Airframe, p. 15-3
Why are deicing boots on larger turboprops inflated in sections?
Inflating only short sections on each wing at a time keeps any disturbance to airflow from an inflated tube to a minimum. On larger turboprop aircraft, the boot sections along the wing operate alternately and symmetrically about the fuselage, and inflating symmetrically on each side of the fuselage maintains control in flight while deicing occurs.
FAA-H-8083-31B, Airframe, p. 15-12
What should you do if a deicer boot shows weather cracking?
Apply a coating of conductive cement. The cement seals the boot against weather and also dissipates static electricity, so static does not puncture the boot by arcing to the metal surfaces.
FAA-H-8083-31B, Airframe, p. 15-21
Should I run the wipers after accidentally applying repellent to dry glass?
No. If the rain repellent system is operated on a dry windshield by mistake, do not operate the windshield wipers or rain-clearing system, because that tends to increase smearing. Remove any concentrated repellent or residue with a thorough fresh-water rinse at the earliest opportunity.
How can I rehearse the spoken answer?
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