How are aircraft AC generators typically driven to maintain 400 Hz, and what control mechanisms ensure frequency stability?

• A. Driven by engines via constant speed drive or integrated drive; frequency controlled by maintaining constant generator speed with CSD and droop characteristics.
• B. Driven by the aircraft’s main hydraulic pump; frequency controlled by external stabilizer.
• C. Driven by piston engine crankshaft with variable-speed control; frequency controlled by regulating generator voltage output.
• D. Driven by electrical turbine starters; frequency controlled by using a phase-locked loop.

Answer: (A)