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Trip-free circuit breakers

Aviation Mechanic Airframe (AMA) practice question 20 of 24 on Aircraft Electrical Systems. ACS element AM.II.K.K6 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONA resettable circuit breaker that opens its circuit during an overload regardless of the position of the operating control is described as

  1. Aautomatic reset
  2. Btrip-free
  3. Ccurrent limiting
Show the answer and explanation

Correct answer: B. trip-free

  • A — incorrect Automatic reset breakers reset themselves and should not be used as circuit protection devices in aircraft.
  • B — correct Breakers that open the circuit regardless of the position of the operating control when an overload or fault exists are called trip-free.
  • C — incorrect A current limiter is a high-amperage fuse used between buses, not a name for this breaker characteristic.

BACKGROUND

Conductors should be protected with circuit breakers or fuses located as close as possible to the electrical power source bus, and the protective device should open the circuit before the conductor emits smoke. Unlike a fuse, which operates once and then must be replaced, a circuit breaker is an automatically operated switch that can be reset. All resettable circuit breakers should open the circuit in which they are installed regardless of the position of the operating control when an overload or circuit fault exists, and such breakers are referred to as trip-free. Automatic reset circuit breakers reset themselves and should not be used as circuit protection devices in aircraft. When a breaker trips, the circuit should be checked and the fault removed before it is reset.

STUDY TIP

Learn the term trip-free as the property that a breaker cannot be held closed on a faulted circuit, and remember that self-resetting breakers are not acceptable protection.

KEY POINTS

  • Trip-free breakers open on a fault no matter where the control is held.
  • Automatic reset breakers are not acceptable as aircraft circuit protection.
  • Check the circuit and clear the fault before resetting a tripped breaker.

SOURCES

  • sources/ama-airframe/ch09.txt "Circuit Breakers"
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MORE ON AIRCRAFT ELECTRICAL 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.