The Boeing CH-47 Chinook helicopter’s engine is controlled by a Full Authority Digital Engine Control System, comprising of two main components; a hydromechanical Unit (HMU) and a Digital Electronic Control Unit (DECU). The DECU is installed in the aircraft to primarily reduce pilot workload in controlling engine exhaust gas in order to achieve the fixed RPM with balanced engine output torques.

The DECU is an electronic control unit that consists of four interconnected printed circuit boards contained in a cast and machined aluminium box. All signals in and out of the unit pass through two circular connectors mounted at the end of the box. The third connector is a serial communications port.

On the top surface of the unit there is a window on the case which displays fault code information from the system in two character hexadecimal to the operator.

Also included on the case are two pressure transducers, one which measures ambient air pressure whilst the other is connected to the compressor discharge pressure on the engine via a pipe.

All signals entering or exiting the DECU are filtered by the RFI circuit board inside the unit for protection against radio frequency interference and lightning. The RFI circuit board also allows the software to detect input lines becoming open circuit.