Author Topic: AIM-9B: The PAF's first missile  (Read 3279 times)


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AIM-9B: The PAF's first missile
« on: January 07, 2018, 04:03:15 PM »
Administrator's note: See also: SAA-LIFT Munitions Lot 1: AIM-9L



The Beginning - the AIM-9B

The AIM-9 traces its earliest ancestry to the US Naval Weapons Center at China Lake, in the Mojave Desert. THe NWC initiated, in the early fifties, a program to design a heatseeking air intercept missile for the intercept of bombers by naval interceptor aircraft, until then armed with either .50 cal or 20 mm guns. The fledgling missile was aptly named after the Sidewinder, a desert rattlesnake which detects its prey by sensing the animal's heat emissions.

            The result was a compact lightweight cruciform canard weapon, which used a solid propellant rocket motor, a fragmentation warhead and an uncooled optical seeker.

            The Sidewinder's seeker used an ingeniously clever optical arrangement, with a Cassegrainian mirror fitted with a tilted secondary mirror. The secondary mirror rotated in unison with a reticle, projecting the whole instantaneous field of view of the mirror through the reticle onto a filter/detector assembly. Because the mirror secondary was tilted, rotating it about the missile's axis swept the cone of the mirror's field of view about the missile's axis in a fashion analogous to a conical scanning radar seeker (see diagram).

            The missile used a 2.5" glass dome nose window, transparent to 1 micron band radiation, providing with the gimballed seeker for a 25 degree seeker field of view. The mirror assembly provided a 4 degree instantaneous field of view (IFOV), projected on to a PbS (Lead Sulphide) uncooled detector. Because of the design of the optical system, the AIM-9B was strictly a tail aspect weapon, as it was blind to anything cooler than a tailpipe. The modest 11 deg/sec seeker tracking rate limited the weapon to non-maneuvering targets. All seeker electronics were built from vacuum tubes. A hot gas generator provided actuator power for the nose canards, and was limited to a 20 sec burn duration before exhaustion. Unlike other missiles of the day, the Sidewinder did not employ active roll stabilisation (via gyros and differential control input), instead employing rollerons, ie slipstream spun metal discs embedded in the trailing edge of the wingtips, which acted as four tiny gyros stabilising the missile mechanically. The engineer who thought of that certainly earned his paycheck.

            The AIM-9B used a fragmentation warhead triggered by a passive infrared proximity fuse. The Thiokol Mk.17 solid propellant rocket delivered 8,200 lb-sec of impulse with a burn duration of 2.2 seconds.

            While by modern standards the AIM-9B is a very limited weapon, it had no serious competitors in its day and was soon adopted by the USAF and NATO as a standard weapon, with no less than 40,000 guidance units built by Ford Aerospace, the prime contractor. The RAAF also adopted the missile, fitting it to the CAC Avon-Sabre, and subsequently the Mirage.

            NATO rounds were mainly built by West Germany's FGW, who evolved an improved subtype designated the AIM-9B-FGW Mod.2. This AIM-9B used solid state electronics, carbon dioxide seeker cooling, a new nose dome and better optical filtering, the latter providing for much better seeker sensitivity.

            The Sidewinder was by the early sixties the principal heatseeker in Western service and as such first drew blood over North Vietnam, there used by the USAF and USN. Its early combat record was not spectacular, as the seeker performance limitations were exacerbated by the poor reliability of the tube electronics and the inexperience of its users, who until then trained for intercepts rather than dogfights. Kill probabilities were in the tens of percent, very sensitive to how well the launch aircraft was positioned. Designed to intercept lumbering bombers, the AIM-9B was ill suited to knife-fights with MiG-17s at low level. Its launch load factor limit of 2G hampered aircrew, while its seeker very often locked on to the sun or clouds, subsequently sending the missile ballistic. The range limit of 2.6 NM meant that the launch aircraft had to be quite properly positioned for a shot, and the pilot very careful about closure rate and range.

            Nevertheless, no less than 28 MiGs were killed for 175 launches between 1965 and 1968, by USAF F-4C/D aircraft, an aggregate P[k] (kill probability) of 16%.


The first missile arrives. Photo c/o of the Francis Neri albums


Photos from various Timawans over the years

« Last Edit: January 07, 2018, 04:15:39 PM by adroth »