by Jonathan M. Stern
The attitude indicator, turn coordinator, and heading indicator are gyroscopic instruments.
Each instrument uses a gyroscope to maintain its orientation relative to one or more of the axes of the airplane while at rest on the ground. In order for the gyroscopes to function, they must spin within a predetermined speed range. The gyroscopes in the Cessna are powered by an engine-driven vacuum pump, in the case of the attitude indicator and heading indicator, and a direct current electric motor, in the case of the turn coordinator.
The DC-powered turn coordinator provides a backup should the vacuum pump fail. This is indicated on the Flight Simulator Cessna 182 turn coordinator by the D.C. Elec. label. As you will see later, the vacuum pump on the Flight Simulator Cessna can be failed.