Decoy flares, as commonly used by military aircraft, work by generating a heat signature in excess of the launch vehicle’s jet engines. This has the effect of confusing any incoming heat-seeking missile’s homing system into locking on to the flares’ signatures instead of the aircraft’s, causing it to explode at a safe distance and saving the pilot’s life.
There are two main types of countermeasure flare – pyrophoric and pyrotechnic. The former is activated automatically on contact with air and the latter by the mechanical removal of a friction cap prior to firing. Pyrotechnic flares use slow-burning fuel-oxidizer mixtures to generate heat, such as MTV (magnesium/Teflon/Viton), while pyrophoric variants use either ultra-fine, aluminium-coated iron platelets or liquid compounds such as triethylaluminium.
The composition of either type of flare is often tailored to counter specific missile systems or to mimic the launch jet’s heat signature.
All military aircraft being built today are fitted with automatic flare dispensing systems, which actively track incoming missiles and launch flares accordingly at optimal range to avert damage, while older or civilian aircraft usually require the pilot to activate the flare launches manually. Systems are fairly flexible and flares can be dispensed one at a time, over long or short intervals and even, if desired, in large clusters.