Countermeasures are systems that allow a vehicle to counter a threat or defeat targeting systems.
Types of countermeasure
- Flares are infrared countermeasures fired off by aircraft to counter infrared homing (heat-seeking) missiles. A flare is considered a decoy, depending on the material it is made from to either burn as hot or hotter than the aircraft's exhaust in an attempt to cause the missile to target it. Typically flares are fired off in multiples to increase chances of distracting the incoming missile from its intended target. Some aircraft have access to "large calibre" flares, which are individually more effective than normal flares at the expense of being able to carry fewer of them.
- Chaff refers to clouds of fibres (often metal or plastic) released by aircraft to create false radar signatures. The signals reflect off the chaff, causing new decoy signatures to appear on radar, which can cause an active radar lock to switch to tracking them instead and disguise the real target in their midst. Some aircraft have access to "large calibre" chaff, which are individually more effective than normal chaff at the expense of being able to carry fewer releases. Note that chaff is typically ineffective against pulse-Doppler radars, as it slows down extremely quickly once released and can thus be filtered out by the radar (much like ground clutter).
- Infrared countermeasures include light energy emitted from non-coherent flashlamps and direct it towards an incoming missile in an attempt to blind the missile's infrared sensors. Low-powered infrared carrier signals emitted from the flashlamps flood the missile's infrared receivers and "confuse" the missile and cause it to follow a false target or a high-powered infrared carrier will blind the missile causing it to lose its target lock.
- Hover Infrared Suppressor System is a helicopter-specific modification that allows it to reduce or almost eliminate all infrared radiation emitted by exhaust gases to the surroundings, especially the helicopter body itself. "Hot spots" on a helicopter caused by the operating engine or the engine exhaust when directed onto the helicopter or helicopter body causes the infrared target of the helicopter to become larger and easier for infrared missiles to lock onto. Changes in the helicopter body to dissipate this infrared energy away from the helicopter reduces the infrared signature of the helicopter making infrared locks less effective and the usage of flares and IRCM more effective.
The Shooting Range #164 - Tactics & Strategy section at 09:26 discusses helicopter defence systems.