Air combat has virtually ceased to exist outside of training exercises, but the proliferation of surface-to-air guided missiles has ensured that aircraft are still shot down. In the past quarter-century, over three quarters of shoot-downs have been by low-cost, widely available infrared homing, man-portable air-defence systems (Manpads).
The severity of this threat is believed to have been a major factor in the US Army's decision not to deploy the Boeing AH-64 Apache to Kosovo in 1999. There are suggestions that the threat may push military helicopter cruise altitudes over southwest Asia to much higher levels.
It would be difficult to overstate the importance of defensive aids suites for many manned aircraft and the larger drones. This also applies to commercial transports and business jets, although accounts of around 30 civil aircraft having been shot down by Sams since 1970 (with over 1000 lives lost) include at least two major non-Manpads accidents: the US Navy's destruction by SM-2 of an Iran Air A300 in 1988 (290 lost) and the Ukrainian Navy's destruction by S-200 (SA-5) of a Siberia Airlines Tu-154 in 2001 (77 lost).
The majority of Mapads available to resistance forces may now be time-expired, and their single-shot kill-probability may be small, but hundreds of thousands have been manufactured (around 10,000/yr in the 1980s), and the danger is real.
However, defensive aids suites are only one factor in minimising aircraft attrition due to enemy actions. Signature reduction, passive defences (armour protection and self-sealing tanks), the support of other airborne and ground-based assets and risk-reduction tactics must also be addressed.
Regarding tactics, it is arguable that the Lockheed Martin F-117A stealth aircraft would not have been shot down (in 1998 by an upgraded Serbian Almaz-Antey S-125 Pechora or SA-3), had its missions not been scheduled like a train service.
In the context of an optically directed Manpads attack, the first defensive steps are to sense the missile launch and exhaust plume. When Sams were introduced in Vietnam, launch detection depended initially on operating aircraft in pairs or fours, giving mutual visual cover. Airframe-mounted sensors later provided automatic indication of such attacks, although with more false warnings.
Early warning of possible attack may be provided by detecting an active enemy radar at (or in the vicinity of) the firing point. The aircraft's radar warning receiver (RWR) may then provide the location of the source and nature of the emission, having compared it with a threat 'library' of hostile and friendly radars. Such an RWR may be described as an electronic support measures (ESM) system.
However, networked fighter aircraft and ground defences are able to fire medium- and long-range missiles without prior transmissions from the launch site, thus minimising warning to their targets.
American RWRs fall in the Pentagon's ALR or APR (A = piloted aircraft, L = countermeasures, R = radar, P = passive) designation series. Examples include the Northrop Grumman ALR-67(V) and -67(V)2 Advanced Special Receiver series, of which over 1600 units have been manufactured, primarily for US Navy fighters and attack aircraft. The Raytheon ALR-67(V)3 is used on the F/A-18E/F and has been chosen for the Canadian CF-188 Hornet. The same company's ALR-69A(V), the first all-digital RWR, is on the US Air Force A-10, AC-130, F-16 and MC-130. The Northrop Grumman ALR-93 equips Greek F-16s. The BAE Systems ALR-94 is the ESM system for the F-22. Most US Army...