BL755

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.[2]

The RP-3 was replaced by the Matra-produced 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 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 18-rocket pods for a total of 36 SNEBs.[2] 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.[3]

The SNEB appears to have been fit operationally only once, when it was mounted on some British Army Aérospatiale Gazelles during the Falklands War in 1982, but it appears 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, most used an older Royal Navy 2-inch rocket design instead.[4]

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 700 feet (210 m) 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 1,500 yards (1,400 m). This was right within the engagement envelope of the Shilka. Furthermore, a total of 20 aircraft would be needed to guarantee the 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.[4] As it was later stated:

The effectiveness of modern air defence systems in the field is such that the use of dive bombing or rocket attacks is likely to involve an unacceptable casualty rate.[4]

This led to the issuing of Staff Requirement SR(A)1197 for a new weapon capable of being delivered from very low altitudes, about 300 feet (91 m), while overflying the target area without the need to pop up.[5]

Hunting Aircraft won the contract with what became BL755.[4] The 600 lb (270 kg) weapon looked like a conventional bomb, but contained a total of 147 sub-munitions arranged in seven rows of 21 each. 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.[5]

The weapon reached its initial in-service version with the No. 1 Mk. 4 design of 1973,[5] with carriage on the Hawker Harrier GR.3, SEPECAT Jaguar GR.1 and Blackburn Buccaneer S.2.[6] 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.[7]

It was precisely at this time that the Soviets began introducing the T-72 into service, which had enough armor to defeat the BL755 if it hit the frontal arc of the tank.[5] 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 impacted the tank from the top where it had no problems penetrating the armor. This No. 2 Mk. 1 version, also known as IBL755,[8] remained effective against Soviet armor for the rest of the BL755's history.[5]

BL755 had its first major use during the Falkland's war, where it was extensively used by the Hawker 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.[6]

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 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.[5]

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 1,500 yards, the CRV7 is effective to about 20,000 feet (6,100 m) 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.[3]

The BL755 was used in combat by the Royal Navy and the RAF during the Falklands War, and the RAF during the second Gulf War (Operation Telic) and Bosnian War. During the first Gulf War a small number were deployed by RAF Jaguars.

On the night of 27 October 1991, a Yugoslavian Soko J-22 Orao mistakenly dropped two BL755 Mk.3 bombs on the outskirts of Barcs, a small city in southernmost part of Hungary, causing extensive material damage, but no casualties. The incident led to an emergency upgrade of the Hungarian Air Force, which obtained 28 new MiG-29B fighter jets in exchange for a write-off of ex-Soviet state debt. The Hungarian government also invited NATO's E-3 Sentry AWACS planes to patrol over the Lake Balaton area, keeping a constant radar eye on the Balkan civil war theatre.

The Air Force of Zimbabwe's BAE Hawks were armed with BL755s, which were used against the Rwandan, Ugandan and Congolese rebel forces during the early stages of the Second Congo War, in support of Congolese leader Laurent Kabila.

The Islamic Republic of Iran Air Force heavily used BL755 cluster bombs on Iraqi troop and armour concentrations during the Iran-Iraq War. They were carried by the F-5E, F-5F, F-4D and F-4E Phantoms.

Both Saudi Arabia and the United Arab Emirates have used the BL755 cluster bomb in the Saudi Arabian-led intervention in Yemen and Yemeni civil war (2015–present).[9][10]

• Herriot, David (2009). "A History of Air-To-Surface Rocket Systems" (PDF). Royal Air Force Historical Society Journal: 90–108. ISSN 1361-4231.