Characteristics
A flare is a brightly burning cartridge that is hotter than the engine. A simple heat seeker chooses the hottest source in its field of view — and that is then the flare.
In practiceTransport aircraft and helicopters dispense flares during take-off and landing in threatened areas, sometimes pre-emptively in a fixed programme. That is exactly when they fly low and slow, within MANPADS range, and there is no time to wait for a warning before reacting.
Flares are the IR counterpart of chaff: pyrotechnic cartridges (classically magnesium/Teflon/Viton, "MTV") that burn brightly for a few seconds after ejection and offer an IR seeker (Passive homing) a hotter, more attractive target than the aircraft itself.
The classic operating principle targets the first seeker generations (Division of the infrared spectrum, Passive homing): in essence they measure "where is the strongest IR source in my field of view?" A flare of 2,000+ K radiates (Stefan–Boltzmann, ∝T⁴) many times more strongly than an exhaust of 700–900 K — the seeker gate slides from the aircraft to the flare, the aircraft manoeuvres away, the missile follows the flame.
Characteristics that determine effectiveness:
- Rise time: the flare must reach full intensity within tenths of a second — before it drops out of the seeker's field of view.
- Burn time: a few seconds; long enough to make the missile take the decisive wrong turn.
- Spectral ratio: in which IR bands the energy lies (crucial against modern seekers, Advanced flares).
- Separation: the flare slows down and falls — exactly the kinematic signature on which modern seekers filter again (see below).
- Timing and numbers: flares work best pre-emptively or immediately on a MAWS warning (Missile Approach Warning System), in programmes (several flares at intervals) combined with a break manoeuvre that turns the aircraft's own exhaust away from the seeker.
Flares protect against IR-guided weapons — not against radar-guided or SAL-guided ones. Which threat is coming is often not visible (passive seeker! Passive homing); that is why chaff and flares are often ejected together in programmes. And by day, against modern seekers: one flare is a question, the package (flares + manoeuvre + DIRCM) is the answer.
Advanced flares
Seekers learned to recognise flares; flares learned to disguise themselves. The modern seeker discrimination techniques and the flare answers to them:
| Seeker discrimination | What it sees with a classic flare | The flare's answer |
|---|---|---|
| Two-colour (two IR bands, Division of the infrared spectrum) | the flare burns much "hotter" (its MWIR/LWIR ratio differs from a jet engine) | spectrally matched flares: mixtures that mimic the spectral ratio of an engine |
| Kinematic check | the flare decelerates abruptly and falls | aerodynamic/thrusted flares: fly along with the platform for a while |
| Rise-time check | an unnaturally fast intensity peak | controlled ignition, pre-heated elements |
| Imaging seeker (Passive homing) | a point source vs an aircraft silhouette | large/distributed flares, salvos that fill the image — and above all: DIRCM (Directional Infrared countermeasures) |
Other advanced variants:
- Covert/low-visibility flares: burn mainly in the IR and are barely visible — no fireworks showing your own position to everyone (relevant for transport aircraft and helicopters at night).
- Pyrophoric (special material) decoys: foils/particles that oxidise in air and form an extended, "cooler" heat cloud with an engine-like spectrum.
- Programmable dispensers: the countermeasures computer chooses the type, number and interval based on the threat (MAWS classification) and the aircraft's own kinematics — flares have become ammunition with a fire-control solution.
The common thread is identical to Challenges for chaff: every discrimination the seeker makes is a measurable assumption, and every generation of flares attacks one assumption. Against the latest imaging seekers the leading role shifts from the flare to directed energy: DIRCM.