What is an IDG (integrated drive unit)?

• A. A device that stores electricity
• B. A unit that reduces engine speed
• C. An assembly that combines the AC generator and CSD into a single unit
• D. A server for monitoring

Answer: (B)

An IDG is an integrated drive generator, a single assembly that provides electrical power by combining the AC generator and the constant-speed drive into one unit. It’s driven by the engine through the accessory gearbox, and the constant-speed drive inside keeps the generator RPM steady so the electrical output stays at the correct frequency (typically 400 Hz) as engine speed varies. This integration reduces separate components and provides automatic regulation of power generation. The other descriptions don’t fit: storing electricity points to a battery, reducing engine speed is a separate reduction drive, and a server for monitoring isn’t related to power generation.