The C-17 is equipped with Tracor AN/ALE-47 countermeasure flare dispensers and the Lockheed Martin/ Alliant Techsystems AN/AAR-47 missile warning system.
AN/AAR-47 is a passive missile warning system which detects missiles by detecting the heat emitted in the exhaust during the missile launch and boost phase. The system is composed of a suite of thermal sensors with four photomultipliers, a signal processing unit and a cockpit mounted control indicator. The suite of surface mounted thermal sensors around the aircraft provide 360 degree coverage.
Frequency selection and signal processing techniques are used to minimise the false alarm rate. The system provides a warning to the crew via the cockpit indicator unit of the presence and direction of the missile threat. A signal is automatically sent to the ALE-47 countermeasures dispenser.
AN/ALE-47 is capable of carrying a mix of expendable countermeasures including expendable jammers. The system interfaces to the C-17 aircraft's sensors. The aircrew can select the mode of operation of the dispenser for fully automatic, semi-automatic or manual operation.
The cockpit control unit can be used to input mission data together with the numbers and types of expendable countermeasures systems loaded into the ALE-47. The cockpit controller updates and displays the status of the dispenser and the numbers and types of countermeasures remaining. The ALE-47 is capable of dispensing the new generation active expendable decoys POET and GEN-X in addition to the conventional chaff and flare decoys which are compatible with the previous generation ALE-40 and ALE-39 dispensers.
In fully automatic mode the dispenser receives the threat data from the aircraft's sensor system, selects the appropriate response in the choice of expendable, the dispersal sequence and pattern, and dispenses the selected expendable decoy. The ALE-47 automatically downloads data to programme active expendable decoys before the launch sequence.
In semi-automatic mode the launcher analyses the threat data input, selects the best response and provides a signal to the aircrew that the system is ready. In a fully manual mode the crew are able to select one of six pre-programmed responses in which the quantities, sequences and types of expendables produce the required decoy pattern.