An APU has how many major sections?

An APU has how many major sections?

• A. Three
• B. Two
• C. Four
• D. Five

Answer: (A)

An APU is typically described as having three major sections: the gas-turbine core, the accessory drive section, and the exhaust system. The gas-turbine core includes the compressor, combustor, and turbine; this is the part that generates the mechanical energy and, in doing so, drives the rest of the unit. The accessory drive section houses the starter, generator, fuel pump, lubrication, and other support hardware that use the core’s energy to produce electrical power and support aircraft systems when the main engines aren’t running. The exhaust system directs the spent gases away from the aircraft and helps maintain proper flow and back-pressure for stable operation. These three groups cover the essential functions of an APU, which is why the standard count is three.

An APU is typically described as having three major sections: the gas-turbine core, the accessory drive section, and the exhaust system. The gas-turbine core includes the compressor, combustor, and turbine; this is the part that generates the mechanical energy and, in doing so, drives the rest of the unit. The accessory drive section houses the starter, generator, fuel pump, lubrication, and other support hardware that use the core’s energy to produce electrical power and support aircraft systems when the main engines aren’t running. The exhaust system directs the spent gases away from the aircraft and helps maintain proper flow and back-pressure for stable operation. These three groups cover the essential functions of an APU, which is why the standard count is three.