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Electrothermal propeller deice cycle time

Aviation Mechanic Airframe (AMA) practice question 8 of 9 on Ice and Rain Control Systems. ACS element AM.II.L.K4 · difficulty: applied. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONA twin-engine airplane's propeller deice timer heats the right propeller outer elements, right inner elements, left outer elements, and left inner elements for 30 seconds each. How long is one complete automatic cycle?

  1. A1 minute, 30 seconds
  2. B4 minutes total
  3. C2 minutes
Show the answer and explanation

Correct answer: C. 2 minutes

  • A — incorrect That total covers only three of the four 30-second heating periods in the sequence.
  • B — incorrect Doubling the cycle would require 60 seconds per element group, but each group is heated for 30 seconds.
  • C — correct Four sequential 30-second periods total 120 seconds, which is 2 minutes for a complete cycle.

BACKGROUND

Many propellers are deiced by an electrically heated boot cemented to each blade, supplied with current through a slip ring and brush assembly on the spinner bulkhead. Heat loosens the bond, and centrifugal force from the spinning propeller together with the air blast breaks the ice particles free. On one aircraft model the boots are heated in a preset sequence controlled automatically by a timer: 30 seconds for the right propeller outer elements, 30 seconds for the right propeller inner elements, 30 seconds for the left propeller outer elements, and 30 seconds for the left propeller inner elements. Once the system is turned on to automatic, it cycles continuously, and a manual bypass of the timer is provided.

STUDY TIP

For timed deice systems, write the sequence out and add the intervals rather than guessing. Also remember that the propeller system is heat plus centrifugal force, not mechanical inflation.

KEY POINTS

  • Propeller deice boots receive current through slip rings and brushes at the spinner bulkhead.
  • A timer heats outer and inner elements of each propeller for 30 seconds apiece.
  • Four 30-second steps make a 2-minute cycle that repeats continuously in automatic.

SOURCES

  • sources/ama-airframe/ch15.txt — "Electrothermal Propeller Device System"
Practice the Aviation Mechanic Airframe (AMA) test →Timed 100-question exam, by ACS area, or review your misses. Free.
MORE ON ICE AND RAIN CONTROL SYSTEMS

SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-31B Aviation Maintenance Technician Handbook – Airframe, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.