Test set for testing as a unit an amplifier system having several modules

An Automatic Flight Control System for helicopter control includes an amplifier unit having several modules, some of which are in duplicate. The tester comprises plugs with test jacks for connection to an amplifier unit and to a normal flight director indicator, so that the amplifier unit may be tested as a unit the way it is used in the aircraft. The tester includes an AC signal source for jumpering to test jacks to simulate input signals, resistors to simulate the servomechanism load, a heading simulator, and switches to simulate system connections of direct-current power for the different functions. The tester has the capability to test all circuits in the chassis and simulate all input signals used on the aircraft, while monitoring and comparing the dual channel outputs. It provides a method of detecting marriage problems between the altitude module, the altitude integrator module, and the rest of the amplifier unit.