The RP-3 (from Rocket Projectile 3 inch) was a British air to ground rocket projectile introduced during the Second World War. The "3 inch" designation referred to the nominal diameter of the rocket motor tube. The use of a 60-pound (27 kg) warhead gave rise to the alternative name of the "60-pound rocket". Though primarily an air-to-ground weapon, it saw limited use in other roles. They were generally used by British fighter-bomber aircraft against targets such as tanks, trains, motor transport and buildings, as well as by Coastal Command and Royal Navy aircraft against U-boats and ships.
Use continued post-war, with the last known major operational use being during the Aden Emergency in 1964, where Hawker Hunters flew 642 sorties and fired 2,508 RP-3s in support of Radforce. Use continued until the withdrawal from Aden in November 1967, at which point the RP-3 was withdrawn from service in favour of the newer SNEB. Concerned about the possibility of shipboard radar setting off the SNEB's electrical ignition, the Royal Navy replaced their RP-3s with a new design, sometimes known as the 2-inch RP. RP-3 - Wikipedia