Definition

An integrated drive generator (IDG) is an aircraft generator combined with a constant-speed drive (CSD) in the same housing.

Description

To provide useable electrical power, an aircraft generator must provide that power at a specific frequency, normally 400 hertz. If a generator were geared directly to the accessory drive of a jet engine, its speed would vary with engine RPM. However, the variable-speed output of the engine is converted to a constant speed by means of a CSD.

In some of the most modern aircraft, generators for each engine are combined with their CSDs in the same unit. This combination is known as an IDG. A malfunctioning IDG can be disconnected from its CSD through a switch on the flight deck. Once disconnected, an IDG cannot be reconnected in flight.