Flare (countermeasure)

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A flare or decoy flare is an aerial infrared countermeasure used by an aircraft 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.

Contents

• Tactics
• Usage
• Decoying
• Materials used
• Pyrotechnic flares
• Pyrophoric flares
• Highly flammable payloads
• See also
• References
• External links

Tactics

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 behind, directly toward the engines. In most cases, pilots have to rely on their wingmen to spot the missile's smoke trail and alert of a launch. Since IR-guided missiles have a shorter 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. Ideally the missile's seeker head is then confused by this change in temperature and flurry of new heat signatures, and starts to follow one of the flares rather than the aircraft.

More modern IR-guided missiles have sophisticated on-board electronics and secondary electro-optical sensors that help discriminate between flares and targets, reducing the effectiveness of flares as a reactionary countermeasure. A newer procedure involves preemptively deploying flares in anticipation of a missile launch, which distorts the expected image of the target should one be let loose. This "pre-flaring" increases the chances that the missile then follows the flares or the open sky in between, rather than a part of the actual defender.

Usage

Apart from military use, some civilian aircraft are also equipped with countermeasure flares, against terrorism: the Israeli airline El Al, having been the target of the failed 2002 airliner attack, in which shoulder-launched surface-to-air missiles were fired at an airliner while taking off, began equipping its fleet with radar-based, automated flare release countermeasures from June 2004. ^{[1] [2]} This caused concerns in some European countries, which proceeded to ban such aircraft from landing at their airports. ^[3]

On 18 June 2017, after an AIM-9X did not successfully track a targeted Syrian Air Force Su-22 Fitter, US Navy Lt. Cmdr. Michael "Mob" Tremel flying a F/A-18E Super Hornet used an AMRAAM AAM to successfully destroy the enemy aircraft. ^[4] There is a theory that the Sidewinder is tested against American and not Soviet/Russian flares. The Sidewinder is used to rejecting American but not Soviet/Russian flares. Similar issues arose from the testing of the AIM-9P model. The missile would ignore American flares but go for Soviet ones due to these flares have "different burn time, intensity and separation." ^{[5] [6]}

Decoying

Flares burn at thousands of degrees Celsius, which is much hotter than the exhaust of a jet engine. IR missiles seek out the hotter flame, believing it to be an aircraft in afterburner or the beginning of the engine's exhaust source.

As the more modern infrared seekers tend to have spectral sensitivity tailored to more closely match the emissions of airplanes and reject other sources (the so-called CCM, or counter-countermeasures), the modernized decoy flares have their emission spectrum optimized to also match the radiation of the airplane (mainly its engines and engine exhaust). In addition to spectral discrimination, the CCMs can include trajectory discrimination and detection of size of the radiation source.

The newest generation of the FIM-92 Stinger uses a dual IR and UV seeker head, which allows for a redundant tracking solution, effectively negating the effectiveness of modern decoy flares (according to the U.S. Department of Defense). While research and development in flare technology has produced an IR signature on the same wavelength as hot engine exhaust, modern flares still produce a notably (and immutably) different UV signature than an aircraft engine burning kerosene jet-fuel.

Materials used

For the infrared generating charge, two approaches are possible: pyrotechnic and pyrophoric as stored, chemical-energy-source IR-decoy flares contain pyrotechnic compositions, liquid or solid pyrophoric substances, or liquid or solid highly flammable substances. ^[7]

Upon ignition of the decoy flare, a strongly exothermal reaction is started, releasing infrared energy and visible smoke and flame, emission being dependent on the chemical nature of the payload used.

There is a wide variety of calibres and shapes available for aerial decoy flares. Due to volume storage restrictions onboard platforms, many aircraft of American origin use square decoy flare cartridges. Nevertheless, cylindrical cartridges are also available onboard American aircraft, such as MJU 23/B on the B-1 Lancer or MJU-8A/B on the F/A-18 Hornet; however, these are used mainly onboard French aircraft and those of Russian origin (e.g. PPI-26 IW on the MiG 29).

Square calibres and typical decoy flares:

• 1x1x8 Inch e.g. M-206, MJU-61, (Magnesium/Teflon/Viton (MTV) based) M-211, M-212 (spectral flares)
• 2x1x8 Inch e.g. MJU-7A/B (MTV based), MJU-59/B (spectral flare)
• 2x2.5x8 Inch e.g. MJU-10/B (MTV based)

Cylindrical calibres and typical decoy flares:

• 2.5 Inch e.g. MJU-23/B (MTV based)
• 1.5 Inch e.e. MJU 8 A/B (MTV based)
• 1 Inch e.g. PPI 26 IW

Pyrotechnic flares

Pyrotechnic flares use a slow-burning fuel-oxidizer mixture that generates intense heat. Thermite-like mixtures (e.g. Magnesium/Teflon/Viton [MTV]), are common. Other combinations include ammonium perchlorate/anthracene/magnesium, or can be based on red phosphorus.

To adjust the emission characteristics to match closer the spectrum of jet engines, charges on the base of double base propellants. These compositions can avoid the metal content and achieve cleaner burning without the prominent smoke trail.

Blackbody payloads

Certain pyrotechnic compositions, for example MTV, give a great flame emission upon combustion and yield a temperature-dependent signature and can be understood as gray bodies of high emissivity (${\displaystyle e}$~0.95). Such payloads are called blackbody payloads. Other payloads, like iron/potassium perchlorate pellets, only yield a low flame emission but also show temperature-dependent signature. ^[8] Nevertheless, the lower combustion temperature as compared to MTV results in a lower amount of energy released in the short-wavelength IR range. Other blackbody payloads include ammonium perchlorate/anthracene/magnesium and hydroxyl-terminated polybutadiene (HTPB) binder. ^[9]

Spectrally balanced payloads

Other payloads provide large amounts of hot carbon dioxide upon combustion and thus provide a temperature-independent selective emission in the wavelength range between 3 and 5 μm. Typical pyrotechnic payloads of this type resemble whistling compositions and are often made up from potassium perchlorate and hydrogen lean organic fuels. ^[10] Other spectrally balanced payloads are made up similarly as double base propellants and contain nitrocellulose (NC), and other esters of nitric acid ^[11] or nitro compounds as oxidizers such as hexanitroethane and nitro compounds and nitramines as high-energy fuels. ^[12]

See also

• Anti-aircraft
• Anti-ballistic missile
• Countermeasure
• Electronic countermeasure

Related Research Articles

A flare, also sometimes called a fusée, fusee, or bengala, bengalo in several European countries, is a type of pyrotechnic that produces a bright light or intense heat without an explosion. Flares are used for distress signaling, illumination, or defensive countermeasures in civilian and military applications. Flares may be ground pyrotechnics, projectile pyrotechnics, or parachute-suspended to provide maximum illumination time over a large area. Projectile pyrotechnics may be dropped from aircraft, fired from rocket or artillery, or deployed by flare guns or handheld percussive tubes.

A solid-propellant rocket or solid rocket is a rocket with a rocket engine that uses solid propellants (fuel/oxidizer). The earliest rockets were solid-fuel rockets powered by gunpowder; The inception of gunpowder rockets in warfare can be credited to the ancient Chinese, and in the 13th century, the Mongols played a pivotal role in facilitating their westward adoption.

An air-to-air missile (AAM) is a missile fired from an aircraft for the purpose of destroying another aircraft. AAMs are typically powered by one or more rocket motors, usually solid fueled but sometimes liquid fueled. Ramjet engines, as used on the Meteor, are emerging as propulsion that will enable future medium- to long-range missiles to maintain higher average speed across their engagement envelope.

Tracer ammunition, or tracers, are bullets or cannon-caliber projectiles that are built with a small pyrotechnic charge in their base. When fired, the pyrotechnic composition is ignited by the burning powder and burns very brightly, making the projectile trajectory visible to the naked eye during daylight, and very bright during nighttime firing. This allows the shooter to visually trace the trajectory of the projectile and thus make necessary ballistic corrections, without having to confirm projectile impacts and without even using the sights of the weapon. Tracer fire can also be used as a marking tool to signal other shooters to concentrate their fire on a particular target during battle.

Flash powder is a pyrotechnic composition, a mixture of oxidizer and metallic fuel, which burns quickly (deflagrates) and produces a loud noise regardless of confinement. It is widely used in theatrical pyrotechnics and fireworks and was once used for flashes in photography.

Man-portable air-defense systems are portable surface-to-air missiles. They are guided weapons and are a threat to low-flying aircraft, especially helicopters.

Infrared homing is a passive weapon guidance system which uses the infrared (IR) light emission from a target to track and follow it seamlessly. Missiles which use infrared seeking are often referred to as "heat-seekers" since infrared is radiated strongly by hot bodies. Many objects such as people, vehicle engines and aircraft generate and emit heat and so are especially visible in the infrared wavelengths of light compared to objects in the background.

A pyrotechnic colorant is a chemical compound which causes a flame to burn with a particular color. These are used to create the colors in pyrotechnic compositions like fireworks and colored fires. The color-producing species are usually created from other chemicals during the reaction. Metal salts are commonly used; elemental metals are used rarely.

An infrared countermeasure (IRCM) is a device designed to protect aircraft from infrared homing missiles by confusing the missiles' infrared guidance system so that they miss their target. Heat-seeking missiles were responsible for about 80% of air losses in Operation Desert Storm. The most common method of infrared countermeasure is deploying flares, as the heat produced by the flares creates hundreds of targets for the missile.

The AN/ALQ-144, AN/ALQ-147, and AN/ALQ-157 are US infrared guided missile countermeasure devices (IRCM). They were developed by Sanders Associates in the 1970s to counter the threat of infrared guided surface-to-air missiles like the 9K32 Strela-2. While decoy flares were effective at jamming first generation infra-red guided missiles, each flare was only effective for a short period. If an aircraft needed to loiter over a high risk area or was flying slowly, it would require a large number of flares to decoy any missile fired at it. The IRCM provided constant protection against infra-red guided missiles.

A pyrotechnic composition is a substance or mixture of substances designed to produce an effect by heat, light, sound, gas/smoke or a combination of these, as a result of non-detonative self-sustaining exothermic chemical reactions. Pyrotechnic substances do not rely on oxygen from external sources to sustain the reaction.

Magnesium/Teflon/Viton (MTV) is a pyrolant. Teflon and Viton are trademarks of DuPont for polytetrafluoroethylene, (C₂F₄)_n, and fluoroelastomer, (CH₂CF₂)_n(CF(CF₃)CF₂)_n.

A pyrolant is an energetic material that generates hot flames upon combustion. Pyrolants are metal-based pyrotechnic compositions containing virtually any oxidizer. The term was originally coined by Kuwahara in 1992, in a paper on magnesium/Teflon/Viton, to distinguish between compositions that serve as propellants and those yielding hot flames which are not necessarily suitable for propellant purposes.

In pyrotechnics, a pyrotechnic initiator is a device containing a pyrotechnic composition used primarily to ignite other, more difficult-to-ignite materials, such as thermites, gas generators, and solid-fuel rockets. The name is often used also for the compositions themselves.

Civil Aircraft Missile Protection System (CAMPS) is an infrared countermeasure against infrared-homed anti-aircraft missiles, specifically designed to defend civilian aircraft flying under 15,000 feet (4,600 m) against MANPADS.

Infrared signature, as used by defense scientists and the military, is the appearance of objects to infrared sensors. An infrared signature depends on many factors, including the shape and size of the object, temperature, and emissivity, reflection of external sources from the object's surface, the background against which it is viewed and the waveband of the detecting sensor. As such there is no all-encompassing definition of infrared signature nor any trivial means of measuring it. For example, the infrared signature of a truck viewed against a field will vary significantly with changing weather, time of day and engine loading.

A missile approach warningsystem (MAW) is part of the avionics package on some military aircraft. A sensor detects attacking missiles. Its automatic warning cues the pilot to make a defensive maneuver and deploy the available countermeasures to disrupt missile tracking.

The Beechcraft MQM-107 Streaker is a reusable, turbojet powered, target towing drone primarily used by the United States Army and the United States Air Force for testing and training. The US Army uses the drone for testing various surface-to-air missile systems such as the FIM-92 Stinger and the MIM-104 Patriot. The US Air Force uses them in practice engagements for their air-to-air missiles like the AIM-9 Sidewinder and the AIM-120 AMRAAM.

The EuroDASS Praetorian DASS is an integral part of Eurofighter Typhoon defensive Aid Sub-System (DASS) providing threat assessment, aircraft protection and support measures in extremely hostile and severe environments. As the DASS is fully integrated, it does not require additional pods that take up weapon stations or would influence the aircraft's aerodynamic performance. In addition the modular nature of the DASS simplifies future upgrades and allows each partner nation or export customer the option to tailor the DASS to their individual needs.

An environmentally friendly red-light flare was a pyrotechnic (firework) flare which used lithium-based formulations that emitted red light. A flare is used for signaling, illumination, or defensive countermeasures in civilian or military applications. It is based on a non-hygroscopic dilithium nitrogen-rich salt that served as an oxidizer and red colorant. The U.S. Army Research Laboratory and the Ludwig Maximilian Institution were credited as the research facilities for developing this product announced in January 2018.

References

External links

• Media related to Decoy flares at Wikimedia Commons