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

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)