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Inverter AC bus distribution

Aviation Mechanic Airframe (AMA) practice question 5 of 24 on Aircraft Electrical Systems. ACS element AM.II.K.K5 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONMany aircraft inverters supply both 26-volt AC and 115-volt AC. If an aircraft uses both voltages, how must the power be distributed?

  1. AOn separate 26- and 115-volt AC buses
  2. BOn one shared AC bus fed through a transformer
  3. COn the DC bus, with each load tapping 26 volts
Show the answer and explanation

Correct answer: A. On separate 26- and 115-volt AC buses

  • A — correct When both voltages are used, the power must be distributed on separate 26-volt and 115-volt AC buses.
  • B — incorrect A single shared bus is not used; the two voltages are kept on their own buses.
  • C — incorrect An inverter feeds an AC distribution bus; its output does not go back onto the DC bus.

BACKGROUND

Some electrical systems operate only on AC, so many aircraft carry an AC system alongside the DC system. Inverters are commonly used when only a small amount of AC is needed, and they may also serve as a backup AC source on aircraft that have an AC alternator. A modern inverter is a solid-state device that takes DC power and feeds power to an AC distribution bus. Many inverters supply both 26-volt AC and 115-volt AC, and an aircraft may be designed to use either voltage or both at once. If both are used, the power must be distributed on separate 26-volt and 115-volt AC buses.

STUDY TIP

Remember the inverter's direction of conversion, DC in and AC out, and that two output voltages mean two separate AC buses.

KEY POINTS

  • An inverter is a solid-state device that converts DC to AC.
  • Many inverters supply both 26-volt AC and 115-volt AC.
  • Using both voltages requires separate 26- and 115-volt AC buses.

SOURCES

  • sources/ama-airframe/ch09.txt "Power Systems"
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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.