Transport aircraft self-protection.

Author:Peruzzi, Luca

In the weeks that preceded the launch of air operations over Libya, a number of Nato countries, reportedly Germany, Great Britain and Italy, deployed Transall Cl60s and C130Js in challenging missions inside Libyan territory, landing on strips and airfields near oil camps to extract national and international citizens and workers. The British and Italian C-130Js (the Italians landed on Sabha airport around 640 km south of Tripoli) flew in a fast evolving theatre of operations, characterized by a variety of air defence surveillance radars, electromagnetic and infrared missiles, without threat detection systems.

Amongst the eagerly awaited weapons on the ground in Libya were the latest and most effective man-portable missiles, namely the SA-18 Igla and SA-24 Igla-S. These became a prime target of recovery operations by American and Nato forces at the end of the conflict, as unknown quantities of these missiles were purloined out of Libya to enlarge the illegal market that feeds terrorist organizations and paramilitary forces. The Libyan crisis was the last one in a series of conflicts (starting with the Balkans wars) in which transport aircraft were required to operate in enclaves surrounded by hostile forces and well within range of radar and infrared guided weapons. The threat remained high not only for the military but also for the civilian fleets.

Since the late Soviet era years the man-portable missile threat has evolved through four generations:

* The Russian SA-7A Strela-2 e SA-7B Strela-2M, the Chinese HN-5A, the Pakistani Anza Mk1 and the American FIM-43 Redeye (the Block II has a gas-cooled seeker positioning it between 1st and 2nd generation) belong to the 1st generation equipped with an uncooled seekers, characterized by a rotating rectangular field of view (FoV) with a single detector element, which led to their increased inaccuracy as they neared the target, or in tail-chase configurations, not to mention their vulnerability to flares.

* The FIM-92A Stinger Basic, the Strela-2M/A, SA-14 Strela-3, the Chinese HN -5B, QW-1, FN-6, the Pakistani Anza Mk II and the Iranian Misagh-1 are 2nd generation weapons equipped with a cooled detector and a conical scanning search technique, which eliminates the above mentioned inaccuracies. They feature all-aspect capabilities, some resistance to flares and offer relatively higher single-shot kill probability.

* The 3rd generation, to which the American FIM-92B/C/E Stinger Post/RMP/Block 1, the Russian SA-16 Igla-1, SA-18 Igla and SA-24 Igla-S, the Polish Grom-1/2, the Chinese QW-11/18/2, FN-16, the Pakistani Anza Mk III and the Iranian Misagh-2 belong together with the (then) Matra Mistral 1 and 2 systems, are characterized by their cooled, dual-channel IR or combined IR/UV detector with a rosette scanning a very narrow FOV pattern (also known as quasi-imaging) providing all-aspect engagement, high resistance to flares, better unfavourable conditions discrimination capabilities and high single-shot kill probabilities.

* The 4th generation includes the Japanese Kin-SAM Type 91 and the Chinese QW-4 that are equipped with full-imaging IR seekers that yield very high resistance to flares and decoys. Command to line-of-sight and beam-riding missiles like the Blowpipe, Javelin and Starburst belong to a different league.

Until the 1990s, to protect low-speed tactical and strategic transport aircraft generating a large heat signature and radar cross section, a typical EW suite would have included a radar warning receiver (RWR), a passive ultraviolet missile warning system (MWS) and a countermeasures (chaff/flare) dispensing system (CMDS), although some platforms modified to conduct a variety of missions for special forces, combat search and rescue and command and control, psychological and electronic intelligence gathering missions, were however equipped with a more robust EW suite. However, the advent of new-generation weapons sparked off the need for improved suites, ranging from advanced MWS to new flares and flare patterns, in addition to fixed and, later directional, infrared countermeasures now known as Dircm.

Flares have been used as countermeasures for almost half a century to lure a man-portable missile away from its target. They come in a large array of shapes and sizes and with a variety of functions and are designed to present a more attractive IR signature than that of the target. They may also be used to confuse the threat by saturating its processing or discrimination circuitry. A chemical energy source (pyrotechnic or pyrophoric in nature) is used to provide the required IR radiation. The main reactive pyrotechnic cartridge continues to be the legacy magnesium-teflon-viton (MTV)-based decoy. This first saw service during the Vietnam War, but has been continuously enhanced in terms of performance and safety.

The introduction of dual-spectral flares however, caused the introduction of missile seekers able to discriminate radiation intensities and, as a consequence, to recognise and reject a standard MTV-based flare event. Propelled...

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