Protecting civil aircraft from shoulder-fired missiles

One of the biggest dangers to civil aircraft these days emanates from  Shoulder-Fired Missiles (SFM). An aircraft is most vulnerable to ground fire, while approaching land or after take off, when it is close to the ground and is flying at low speed with no major manoeuvring. A terrorist armed with SFM, operating outside the airfield perimeter, can easily target such aircrafts as they fall well within the range of SFMs and are basically, easy targets.

Consequently, various countries are exploring ways to protect their aircraft from SFM threat. In USA, the Department  of Homeland Security decided to equip the 7,000-plus-fleet of civilian airliners with suitable equipment to provide protection against such missiles. All airliners of El Al, the national airlines of Israel, are already equipped with proper protection systems. Even Singapore Airlines has evinced interest in such a protection system. In fact, all airlines that have operating routes over terrorist-affected areas in Africa, the Middle East, Europe and Asia are also evaluating this concept seriously.

Smart moves
One of the best measures to deal with such threats is the Electronic Counter Measures (ECM), which is designed on the basis of military aircraft systems. This mechanism is devised to disrupt the surveillance systems of the enemy. There are two major ways in which ECM works — decoys and jamming.

Jamming method involves jamming the enemy signals with false transmissions. Decoy method involves the use of flares, especially to counter heat-seeking missiles. One of the biggest advantages of ECM is that no major weaponry has to be loaded into the civil aircraft. And ECM will only deflect the incoming missile away from the aircraft.
But one of the major issues in this measure is that the sensor of the warning device would be required to scan the surface of the earth below the aircraft and ought to be able to distinguish the oncoming SFM  from ground clutter. Some firms have developed Ultra Violet (UV) band sensors to detect the missile exhaust plume. But looking at the frequency spectrum study of the exhaust plume of man-portable air-defense system (MANPADS) and taking into account the atmospheric absorption, others are of the opinion that infra red (IR) band is the most appropriate to detect an incoming SFM. But UV and IR sensors have their negative points too. The system is vulnerable to false alarms, as it can be confused by other heat sources like active chimneys, vehicles, blazing fire on the ground and so on.

It would be worth mentioning here that the SFM moves at supersonic speed and the distance involved for the missile to travel towards the aircraft is small (10 to 20 seconds). So, the protective system must respond within this time frame to prevent the incoming missile from impacting the aircraft. Hence, the passive counter measures include dispensing of chaff i.e., aluminium foil or flares to disrupt the guidance system of the missile, deflecting it away from the aircraft. Active counter measures involve firing of high-power solid-state laser beam towards the incoming missile. It is, of course, expensive and such high power solid-state lasers are available from a few sources only.

Since the time available is limited, the operation of the defence system is required to be totally automated. The pilot would not be required to execute evasive manoeuvres that could endanger the aircraft, if carried out while flying at low speed and low altitude during approach for landing or after take off.

Considering the present situation, there is an urgent need to adopt these technologies for all our civil passenger aircraft.