Decoy flare

A flare or decoy flare is an aerial infrared countermeasure used by a plane or helicopter to counter an infrared homing ("heat-seeking") surface-to-air missile or air-to-air missile. Flares are commonly composed of a pyrotechnic composition based on magnesium or another hot-burning metal, with burning temperature equal to or hotter than engine exhaust. The aim is to make the infrared-guided missile seek out the heat signature from the flare rather than the aircraft's engines.

In contrast to radar-guided missiles, IR-guided missiles are very difficult to find as they approach aircraft. They do not emit detectable radar, and they are generally fired from a rear visual-aspect, directly toward the engines. In most cases, pilots have to rely on their wingmen to spot the missile's smoke trail and alert them. Since IR-guided missiles are inherently far shorter-legged in distance and altitude range than their radar-guided counterparts, good situational awareness of altitude and potential threats continues to be an effective defense. More advanced electro-optical systems can detect missile launches automatically from the distinct thermal emissions of a missile's rocket motor.

Once the presence of a "live" IR missile is indicated, flares are released by the aircraft in an attempt to decoy the missile; some systems are automatic, while others require manual jettisoning of the flares.

The aircraft would then pull away at a sharp angle from the flare (and the terminal trajectory of the missile) and reduce engine power in attempt to cool the thermal signature. Optimally, the missile's seeker head is then confused by this change in temperature and flurry of new signatures, and therefore follows the flare(s) rather than the aircraft. The most modern IR-guided missiles have sophisticated on-board electronics that help discriminate between flares and targets, reducing the effectiveness of countermeasures.

Since insurgents and terrorists are increasingly targeting helicopters with missiles, because helicopters are slower-moving, there is an increasing trend to equip military helicopters with flare countermeasures. "Consequently, flare dispensers are now fitted to helicopters. Indeed almost all of the UK's helicopters, whether they are transport or attack models, are equipped with flare dispenser or missile approach warning systems. Similarly, the US armed forces (in particular the US army) have adopted defensive technology on their helicopters."

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Wikipedia