Previous systems For many years the standard RAF anti-armour weapon was the "60lb"
RP-3, the
Second World War-era air-to-ground rocket used by British aircraft such as the
Hawker Typhoons of the
Second Tactical Air Force. These were still being widely used in the 1960s, especially during the
Aden Emergency in battles between
Yemen and Radforce in what was then the
Aden Protectorate where
Hawker Hunters fired a total of 2,508 RP-3 over 642 sorties. With the British withdrawal in November 1967, the Hunters moved to
Bahrain and the RP-3 was retired after decades of service. The RP-3 was replaced by the 68mm (2.7 inch)
SNEB, a version of the seminal post-war rocket design, the US
Folding-Fin Aerial Rocket (FFAR). These rockets were fired from a streamlined pod made by
Matra (giving it the alternative name) rather than individual rails, which greatly reduced drag and dramatically increased the number of rockets that could be carried. While a Hunter might carry eight RP-3s, it typically carried two M115 18-rocket pods for a total of 36 SNEBs. The SNEB was also more accurate; the RP-3 had an average dispersion around 2.3 degrees, while the larger snap-out fins of the SNEB reduced this to just over 1 degree. However, the smaller rocket motor did result in slightly lower velocity and longer flight times, although the effective range was slightly longer. The SNEB appears to have been used in combat only once, when they were mounted on some
British Army Aérospatiale Gazelle helicopters during the Falklands War in 1982. Records suggest none were actually fired. The SNEB was also cleared for carriage by many other aircraft used in the conflict, but due to the possibility that shipboard
radars might fire the electrical ignitors while in the magazines, most used an older
Royal Navy 2-inch (51 mm) rocket design instead.
SR(A)1197 In the early 1970s the
Ministry of Defence was startled by reports of the effectiveness of the ZSU-23-4
Shilka which first entered service in 1965 and had replaced all earlier systems in Soviet use by the early 1970s. Using older weapons like the 1000 lb GP bomb or the SNEB against tanks required the aircraft to fly low and then "pop up" during the final approach to about altitude and then fly directly at the target. In the case of the SNEB this required a dive at around 10 degrees and firing at a range of about . This was right within the engagement envelope of the
Shilka. Furthermore, a total of 20 aircraft would be needed to guarantee the armour formation would be broken up, meaning the
Shilka would have many chances to attack. This led to serious concerns about the survivability of the RAF in the anti-armour role. As it was later stated: This led to the issuing of
Staff Requirement SR(A)1197 for a new weapon capable of being delivered from very low altitudes, about , while overflying the target area without the need to pop up.
BL755 Hunting Aircraft won the contract with what became BL755. The weapon looked like a conventional bomb, but contained 147 sub-munitions arranged in seven rows of 21 each behind
frangible covers. After release from the aircraft, the "bomb" was popped open using an inflatable bag that drove the munitions outward, breaking the covers and scattering the bombs. The sub-munitions consisted of a small
high explosive anti-tank warhead with a stabilizing "coronet" that flipped out on ejection to ensure they were facing forward when they impacted. The trigger was mounted on a spring that extended after launch to ensure the bomb fired at the right range from the armour. The weapon reached its initial in-service version with the No. 1 Mk. 4 design of 1973, with carriage on the
Hawker Siddeley Harrier GR.3,
SEPECAT Jaguar GR.1,
Blackburn Buccaneer S.2. and
F-4 Phantom. Some indication of its effectiveness compared to the SNEB is that calculations suggested nine aircraft each dropping two BL755s would have the same effect as 20 aircraft firing 36 SNEB each.
IBL755 It was precisely at this time that the Soviets began introducing the
T-72 tank into service, which had enough armour to defeat the BL755 if it hit the frontal arc of the tank. In response, Hunting modified the design to replace the coronet with a small parachute contained in a basket at the back of the sub-munitions. This slowed the weapon so that it normally hit the tank from the top where it had no problems penetrating the armour. This No. 2 Mk. 1 version, also known as IBL755, remained effective against Soviet armour for the rest of the BL755's history.
RBL755 BL755 had its first major use during the Falklands War, where it was extensively used by Harrier aircraft. It was found that when the Safety, Arming and Functioning Unit (SAFU) was set to its lowest altitude setting, the parachutes did not have time to fully deploy and the bomblets often struck the ground at an angle that meant their trigger was not set off. When the RAF began preparing for the
Gulf War in 1991, they decided that all weapons would be released from medium altitudes, which the BL755 was not really suited to given the SAFU was designed for a range of altitudes from low to ultra-low. This led to an Urgent Operational Requirement and the modification of those remaining BL755's with No. 1 Mk. 4 with the addition of a
Motorola radar altimeter to produce the RBL755 – the R for 'radar'. The incorporation of the altimeter meant the weapon always released the sub-munitions at the right time to ensure they had the right trajectory to trigger, which also had the side-effect of eliminating any pre-setting on the part of the pilot.
Replacement As part of the international
Convention on Cluster Munitions carried out in
Oslo in 2007, the UK agreed to remove the BL755 from service. Its replacement was the
CRV7, another rocket developed from the FFAR, but one with a new
solid-propellant rocket of dramatically improved performance. Whereas the RP-3 and SNEB had an effective firing range on the order of , the CRV7 is effective to about and flies at about three times the speed of these earlier weapons. This allows the launching aircraft to fire whilst still outside the range of weapons like the Shilka. ==Design==