Airforces

Germany (IRIS-T), Israel (Python 5), Japan

(AAM-5), South Africa (A-Darter) and the UK

(ASRAAM) have all developed IIR AAMs.

The shift from an infrared to an imaging

infrared seeker is the fundamental difference

between the AIM-9X and all the preceding

Sidewinder variants that reached service entry.

The AIM-9R used an imaging seeker operating

in visual wavelength that limited it to daylight

use only. Test shots were carried out; however,

the project was cancelled in 1991 as a result

of US defence cuts. The development had

also run into considerable technical difficulty.

McLean’s rationale in developing what

would become the AIM-9 is explored in the

definitive history of the weapon, Ron Westrum’s

Sidewinder. McLean’s fundamental insight was

the desirability of moving ‘fire control’ from the

launch platform to the missile. In the late 1940s,

semi-active radar homing was the preferred

guidance mode, with the missile dependent on

the launch aircraft’s fire control radar to illuminate

the target. There were also beneficial cost and

reliability implications to McLean’s approach if,

of course, the seeker could be made to work.

Today’s imaging infrared-guided AAMs are

technologically a long way from the AIM-9B.

Staring or scanning focal plane arrays have

replaced the uncooled lead sulphide (PbS)

hotspot detector of the original Sidewinder,

while today’s missile provides all-aspect

engagements at ranges far in excess of the

early versions. Helmet-mounted sighting

systems are used to better exploit these

missiles’ high-off-boresight capabilities, while

data links are also being introduced on some

to enable lock-on after launch. The present

generation of IIR missiles are also capable

of sustaining g loads in excess of 60g.

The development and adoption of imaging

seeker technology improves the target detection

range by more than a factor of two, compared

with late-generation IR sensors. It provides

for far greater resistance to countermeasures

while allowing the pilot to select an aim point.

Unsurprisingly, this is likely to be the cockpit –

the most vulnerable area in a crewed aircraft.

NATO standardisation

Seven imaging infrared air-to-air missiles are

in service, but the A-Darter had yet to enter

the inventory as of the beginning of 2018.

Three of them can be directly traced back to

the 1980 Family of Weapons memorandum

of understanding (MOU) originally signed

by the US, UK and West Germany – and

later joined by Canada and Norway.

The MOU was intended to progress NATO

standardisation with the US, leading to

development of an active radar-guided

medium-range AAM, the AIM-120 AMRAAM,

while Germany and the UK would provide

the short-range complement, the AIM-132
ASRAAM. Unfortunately, as with many NATO
standardisation efforts, the Family of Weapons
project fell foul of national political and
industrial imperatives, diverging requirements
and technical issues. Germany pulled out
of the programme during 1989, while the
US, Canada and Norway followed in 1990.
The failure of the Family of Weapons
initiative left NATO nations with a capability
gap. UK defence officials warned in 1991
that delays to a Sidewinder successor meant
they were now fielding an inferior weapon
to the R-73. Five years later, the then US
Air Force Chief of Staff, Ronald Fogleman,
described the AIM-9M as the ‘fourth-best’
short-range AAM. This was the last of the
‘classic’ Sidewinder family to enter service.
The basic AIM-9M model entered service in
1982 and featured a two-colour seeker. It had
a greater detection range than the AIM-9L.
The AIM-9M was updated throughout the
1980s and into the early 1990s with the focus
on improved flare rejection capabilities.
Instead of providing NATO with an IIR
AAM on which it could move toward
standardisation, the short-range effort
fragmented. The US eventually pursued the
AIM-9X, the UK carried on with ASRAAM,
and Germany led the IRIS-T programme.
The three designs that emerged to meet the
respective national projects reflected differing
compromises on addressing requirements,
performance and cost needs, even though
each was driven by a common threat baseline,
the R-73. Each weapon adopted a differing
aerodynamic configuration: the UK’s Advanced
Short-Range Air-to-Air Missile (ASRAAM) was
a wingless design that used body lift and
cruciform cropped tail-control surfaces. While
the US AIM-9X continued with cruciform
forward fins and tail control surfaces, these
Above: US Marines assigned to Marine Light Attack Helicopter Squadron 167 load an AIM-9M missile onto
an AH-1W at MCAS New River during a live-fi re exercise last December. USMC/LCpl Cody Rowe
Below: An AIM-9M streaks away from a F/A-18E over the Point Mugu Sea Range. The AIM-9M is a
development of the AIM-9L and replaced the latter on the production line in 1982. USN/Lt Chris Pagenkopf

Above: AIM-9M missiles on the fl ight line at Marine Corps Air Station New River, North Carolina. The

‘Mike’ Sidewinder has a reduced-smoke motor, an updated guidance section, enhanced resistance to

countermeasures and improved overall reliability. US Marine Corps/LCpl Cody Rowe

Short-range air-to-air missiles

64 // MAY 2018 #362