Helicopter Weapons.

Initially adapted from land-launched "hand-guided" systems, hell-borne missiles have come a long way. From semi-automatic command-to-line-of-sight, they have evolved to fully automatic, which affords longer ranges, while a man-in-the-loop facility allows trajectory correction or last-second mission abortion.

The first generation of helicopter-launched weapons was based on command guidance signals, transmitted either along wires unwinding from spools on the missile (as in the cases of the Aerospatiale SS.10/11 and the KBM 9M14 Malyutka or AT-3 Sagger) or by radio (as for the Nudelman 3K11 Falanga or AT-2 Swatter).

With command guidance demanding a skilful, well-trained operator, the next generation used semi-active command to line-of-sight (saclos) guidance. In this case the operator has only to keep a stabilised sight on the target, and a tracker on the launcher measures the deviation of the missile flare from the line-of-sight, allowing corrective signals to be generated automatically.

Tow

The first example was the Raytheon BGM-71 Tow (Tube-launched, Optically-tracked, Wire-guided) missile, which was introduced in Vietnam in 1972. It demonstrated a 77 per cent hit probability, six times that of the SS.11.

Europe's contender for the helicopter-launched weapon market was the Euromissile Hot, which appeared five years later. It uses a similar wire-based saclos guidance, but provides some range increase relative to the Tow.

Both the Tow and the Hot have gone through several stages of development. For example, the Raytheon Tow-2A and Euromissile Hot-2T introduced tandem warheads to defeat explosive reactive armour (ERA). The Hot series employs a telescopic precursor charge to provide optimum stand-off distance.

The Tow-2B is a fly-over, shoot-down missile with a dual-mode sensor and a new warhead section housing two downward-pointing EFPs (explosively-formed penetrators). Over 660 000 Tows have been produced for 44 nations.

The Tow-FF (Tube-launched, Optically engaged, WireLESS Fire & Forget) derivative eliminates the wire and adds an imaging infrared focal-plane array seeker. Aside from allowing the missile to perform autonomously, this also increases hit probability and rate of fire. However, the Tow-FF retains a man-in-the-loop command guidance capability using a radio link. It is reported that the Tow-FF is required to deal with tanks equipped with active protection systems. On 18 September 2000 Raytheon received a $125.9 million 42-month contract covering engineering and manufacturing development. The US army intends to procure 4000 missiles and 1841 modification kits for upgrading the current Itas acquisition system

A problem with saclos guidance arises from the missile being fitted with an aft-mounted flare to make it visible to the tracker on the launch station. In the Iraq-Iran war it was found that early production Tow missiles could be decoyed with flares. The Tow-2B and subsequent models were therefore equipped with a coded xenon beacon in place of the flare, providing, once again, positive missile identification.

Hot

In the case of the Hot, Euromissile deals with the countermeasures problem by means of a new CCD (charge-coupled device) seeker and a bispectral (1- and 10-micron) anti-jamming system. Hot is one of the weapons proposed for Euromissile's Advanced Turret Modular (ATM) system, which provides vehicles such as the Pandur 6 x 6 with a command, control, communication and computing, reconnaissance, intelligence, surveillance, target acquisition (C4RISTA) system for observation, reconnaissance and combat duties. The ATM has a periscope-mounted array of thermal-imaging and television sensors, plus laser ranger and illuminator, and a missile guidance system.

Some 70 French Army Hot-armed Gazelles are now equipped with the Viviane day/night sight. The latest missile variant is the Hot 3, which entered production in 1995, and will first arm the German Army Tiger helicopter. The Hot series has been used operationally in the Iran-Iraq war, the Lebanon, Chad, Western Sahara and the Gulf War. So far, 85 000 Hot missiles have been ordered by 18 countries, together with 720 firing units for helicopters and 820 ground vehicle installations.

Malyutka, Shturm

In extending the life of the KBM 9M14 Malyutka (Baby) or AT-3 Sagger, the original wire-based command guidance system was replaced by saclos, provided in infantry applications by a Lomo LCEM (Land Control Equipment Module). The new KBM Malyutka-2, which rolls in flight, is fitted with two off-axis flares, the rotation of which is detected automatically by the LCEM, thus distinguishing the missile from simple decoys. Countermeasures resistance also benefits from the LCEM field-of-view being reduced as a function of time-of-flight, and from the use of a very narrow waveband. The Malyutka-2 also has uprated rocket motors, giving an increased average speed. It is armed with a tandemcharge warhead, producing twice as much armour penetration, but it can also be fitted with a blast warhead.

Later weapons from KBM include the 9M114 Shturm or AT-6 Spiral, which was standard armament on the Mi-24, and uses radio saclos guidance. The Shturm was developed in the late 1970s and was the first Soviet supersonic (Mach 1.55) weapon. It flies above the line-of-sight, and initiates a dive attack from a point 500 to 700 metres short of the target. In the mid-1990s the system was being promoted in the form of the 9P149 Shturm-S, based on an MT-LB tracked vehicle that carries 12 rounds. The latest missile variant is Shturm Version 2, which has a 7.4 kilogram warhead and a maximum range of 7000 metres, almost twice that of Tow-2. The KBM philosophy is that radio guidance removes the traditional restrictions on missile range and flight speed imposed by the use of trailing wires.

The Shturm, used in Afghanistan, is available with a variety of warheads, including fuel-air explosive. KBM claims that the Ataka (which appears to be basically a Shturm with a tandem warhead) has a guidance that is more jam-resistant than that of KBP's Vikhr.

Vikhr, Ingwe

A laser beam-riding missile is less prone to jamming problems. This form of guidance (the beam being linked to a television/imaging infrared tracker) is used by the tube-launched supersonic KBP 9M120 Vikhr or AT-16 Whirlwind, which peaks at Mach 2.35. Having both contact and proximity fuzes, the Vikhr can also be used against slow-flying aircraft. The company refers to the option of launching two missiles in salvo against a single target. Unlike the missiles discussed earlier, the Vikhr is also suitable for fixed-wing aircraft such as the Su-25.

Laser beam-riding is also used by the Kentron Ingwe (Leopard), which is an upgrade of the earlier ZT-3. The Ingwe is suitable for use from helicopters and ground vehicles, and as an infantry-operated weapon.

One of the limitations of saclos guidance and beam-riding is that miss distance tends to increase with firing range, since the lateral, displacement of the missile from the line-of-sight is measured in terms of an angular error.

A homing missile should theoretically give better accuracy in long-range engagements, a higher firing rate and indirect fire from behind cover. On the other hand, a fire-and-forget missile demands a sore-thumb target, whether this is achieved by natural contrast or (for example) by a laser designator. In very long-range firings it may be necessary to use some form of mid-course guidance (such as laser beam-riding) prior to the terminal homing phase.

Hellfire, Mokopa

Laser spot-homing is inexpensive and precise, and particularly useful in the close support role, allowing forward troops to designate targets that may well be invisible to the launch aircraft. However, it is not a true all-weather system and the beam is now likely to be detected by sensors on the targeted vehicle.

The leader in semi-active laser guidance was the AGM-114 Hellfire from Rockwell (now Hellfire Systems alias Boeing-Lockheed Martin) of which the latest laser version is the AGM-114K Hellfire Optimized Missile System (Homs). This Hellfire II has 40 per cent fewer parts, a significantly improved tandem warhead, a shorter minimum range, and a longer maximum range than earlier models. Its also has a digital autopilot and a seeker that has been hardened against electro-optical countermeasures. It can fly on a lower trajectory below cloud cover, and it is capable of reacquiring targets, having passed through cloud.

The Hellfire has recently been integrated with an Agusta A129 fitted with Tamam's advanced day/night targeting system (NTS-A). Test firings of Hellfire from a US Air Force Special Operations AC-130U gunship are planned for later this year. Lockheed Martin is marketing the Manned Hellfire Turret System (MHTS), a multi-sensor fire control system with four ready-to-fire Hellfire IIs. The MHTS has been integrated on the General Dynamics Pandur light armoured vehicle.

Semi-active laser guidance is also used by the Kentron Mokopa, a weapon that falls in the same category as the Hellfire. Like the latter, a millimetric-wave radar-guided version is being developed. The first airborne firing of a Mokopa from the Rooivalk helicopter (for which it is being developed) took place in September 1999, and guided tests are due to start this year.

Trigat-LR

A fully autonomous missile can be fired into a general area where armour is reported, and left to find, identify and attack a target without further help. This category is particularly well suited to use from fast jet aircraft, the crews of which have extreme difficulty in visually acquiring ground vehicles from a safe distance.

One form of autonomous guidance employs an imaging infrared seeker, which, in principle, can distinguish between a burning tank and one with its engine running, and can prioritise an active vehicle over one with a cold engine. However, it may be noted that the use of thermal imaging as a means of guidance is criticised by some manufacturers, amongst which KBP, on the grounds that it is unsuitable for targets other than tanks.

Infrared homing is employed by the Euromissile Dynamics Group (EMDG) Trigat-LR. The first guided firing from a Panther helicopter took place on March 12, 1998, achieving a direct hit from 2630 metres. Used in conjunction with television and flir sensors on a mast-mounted sight (Osiris), the system can track up to four targets simultaneously, and engage all four within eight seconds. Trigat-LR provides the choice of direct and dive attacks. The parent companies of EMDG are Aerospatiale Matra Missiles, Matra BAe Dynamics and LFK (Eads).

Germany plans to use the Hot-3 and later the Trigat-LR on the Tiger, but is so far the only likely customer for the latter missile. Britain will evidently use both the laser Hellfire and the Longbow version (discussed below) on the WAH-64D, while France will use Hot on the Tiger HAC.

It is possible that some Tiger customers will demand a modern fire-and-forget anti-tank missile, but one that does not require the expensive fire control system of the Trigat-LR. In this context it may be noted that last year Rafael, Diehl, Rheinmetall and STN Atlas formed the Eurospike consortium to market internationally and manufacture in Europe the Rafael-designed Spike family of anti-tank missiles.

The basic member of the Rafael Spike family is the Gill infantry weapon (quod vide), but includes the Rafael NTD, which is specifically designed for use from helicopters. It retains the same basic technology but is much larger (150 mm diameter) and offers a range of 6000 metres. It thus operates in the same basic way as the optical fibre-equipped Spike, i.e. charge-coupled device imaging infrared autotracking, but can be fired either in locked-on or unlocked-on modes. In the latter mode, the target can be acquired later when closer range to the presumed target permits acquisition lock-on. It is now in low-rate production, presumably to equip the Republic of Singapore Air Force's attack helicopters. The missiles would be assembled in-country. Rafael has exhibited an MD 530 helicopter with a four-round Spike pod and a Topaz turret (from the same company), combining television and thermal-imaging cameras and a laser range-finder.

Longbow

One alternative to imaging infrared in developing a fully autonomous weapon is millimetre-wave (MMW) radar, which provides all-weather capability. The first missile in this category is the AGM-114L Longbow Hellfire, which is the responsibility of the Longbow Limited Liability Company, a joint venture by Lockheed Martin and Northrop Grumman. The 1000th Longbow Hellfire was completed in October 1999, and by August 2005 Hellfire LLC will have delivered 10 397 of these missiles under the existing five-year US Army contract.

Studies are being conducted by the US Army and Marine Corps into a Hell fire follow-on, frequently referred to as either the Hellfire 3, Modernized Hellfire (MHF) or the Joint Advanced Weapon System (Jaws). It is to be capable of a range of 20 kilometres, but is not expected to enter service before 2008 at the earliest. One possible form of guidance is a laser radar (ladar) seeker. However, there is as yet no decision on whether the new generation will have a single- or dual-mode seeker. The new missile is required to be compatible with both rotary- and fixed-wing aircraft, the latter including the AV-8B, F/A-18 and JSF.

Polyphem

Since a helicopter is a very expensive, soft and -- in some circumstances -- highly visible target, the risk of attrition favours it being armed with long-range anti-tank guided missiles. Fibre-optic guidance is jam-proof and makes possible precision strikes at ranges in excess of 60 kilometres, but such distances demand a turbine engine and thus result in an expensive missile (though this is partially offset by the fact that no complex seeker is needed onboard the missile). On the other hand, it can carry out reconnaissance on its way to the target and down-link damage assessment video.

In 1994 France, Germany and Italy signed a preliminary agreement to finance a technology demonstration programme based on the fibre-optic guided Polyphem missile. In 1998 there was a further tri-partite agreement (Trifom), leading to service trials in 2001.

This programme is being run on an equal-share basis by Aerospatiale Matra Missiles, Dasa-LFK and Italmissile (a joint venture by Alenia Difesa and FiatAvio). Aerospatiale Matra Missiles is responsible for the rear section, the filament winding and the fire-unit. Italmissile manufactures the launcher, the launch canister and the warhead. The powerplant is currently a Teledyne Continental turbojet.

The first round was fired in 1995, and one year later a C-22 target drone dispensed 60 kilometres of fibre optic cable in flight, without a break. In 1997 a Polphem achieved a one-metre miss distance from a range of 16 kilometres. The first launch of the definitive design took place in September 2000 at Meppen in Germany in September and the next will take place early in 2001. The French Army is considering a six-round wheeled vehicle capable of firing either the Polyphem or the MLRS(G).

The Polyphem has a GPS and laser-based navigation INS and carries a gyro-stabilised imaging infrared camera. The latter operates both in locked or unlocked modes, meaning that the operator can swing the camera as the missile flies along its own course; in the locked mode, the missile is slaved to all operator inputs. The optical system allows the simultaneous transmission of video data from the missile to the ground station and of command data in the other direction, with rates of more than 200 MBytes per second. The missile functions virtually autonomously, the role of the operator being to validate the automatic target selection and adjust the final aim-point.

Europe's Polyphem is regarded as providing the basis for a future family of missiles that could be used from a wide variety of platforms for many purposes (including air defence for submerged submarines).

Until the end of 1999, the US Army had its own optical wire-guided missile project, but it was put on ice due to budgetary constraints in spite of a very advanced stage culminating with a ninth test in 1999. Known as the Raytheon Efogm, this fifteen-kilometre range, rocket-powered missile was specifically intended as an anti-armour weapon for use from Hummer vehicles, although it could also be used against helicopters and other high-value targets.