Name the major sections of a gas turbine APU.

• A. Air intake, compressor, turbine, exhaust, and oil system
• B. Air intake, compressor, combustion chamber, turbine, exhaust, accessory drive gearbox, lubrication system, fuel system, cooling system, electrical generator, and control system
• C. Air inlet, rotor, stator, turbine blades
• D. Fuel system, lubrication system, exhaust stack

Answer: (B)

The major sections of a gas turbine APU include the core flow path—air intake, compressor, combustion chamber, turbine, and exhaust—plus the essential auxiliary systems that support operation: accessory drive gearbox, lubrication system, fuel system, cooling system, electrical generator, and control system. This combination is what makes the APU functional: the air intake feeds the compressor to raise pressure, the combustion chamber mixes fuel with that high-pressure air and burns it to produce hot gases, the turbine extracts energy to keep the compressor running and powers other accessories via the gearbox, and the exhaust releases the processed gases. The auxiliary systems ensure everything runs smoothly and safely: the gearbox drives pumps and the generator, the lubrication system keeps moving parts protected, the fuel system supplies fuel, the cooling system handles heat, the electrical generator provides power, and the control system manages operation and safety.

Other options omit key parts of the system or confuse internal components with major sections. For example, one option leaves out the combustion chamber, control, and several essential subsystems, making it incomplete. Another focuses on internal turbine or rotor/stator elements rather than the overall APU layout, and another lists only a few subsystems. The single comprehensive set best reflects the full structure of a gas turbine APU.