84 with a ballute. Modern British GP bombs The principal modern British bombs are and , and are no longer in service. The smaller 540 lb was retired with the demise of the Harrier GR9 aircraft with the larger 1000 lb being retired in Apr 2019. Currently the UK only uses the 500 lb class Paveway IV weapon system. The warhead is a modified enhanced Mk 82 warhead. Soviet and Russian GP bombs The Russian term for general-purpose bomb is fugasnaya aviatsionnaya bomba (FAB) and followed by the bomb's nominal weight in kilograms. Most Russian iron bombs have circular ring airfoils rather than the fins used by Western types. In 1946 the Soviet Union developed a series of freefall bombs in four sizes , , , and and sharing a single nose and a single tail fuze. The bomb could be dropped from up to and up to ). The original, 1946-series bombs had poor ballistic characteristics at supersonic speed, and their construction was fragile. As an interim measure, upgraded versions of the bombs were built with thicker walls and no nose fuze. The thick-walled version of the bombs were built until 1956. The 1954 series of high-drag bombs was built in six sizes: , , , , , and . A feature of the 1954 series of bombs is the ballistic ring on the nose of the bomb which acts as a vortex generator to aid the bombs stabilizers. The smaller (less than ) bombs had a single nose and a single tail fuze, while the larger weapons shared a single nose fuze and two base fuzes. The FAB-9000 () weapon was roughly comparable to the wartime Grand Slam bomb. It was used by Russian aircraft designers as a substitute for early nuclear weapons when determining the size and clearances of bomb bays. In 1962 a new series of streamlined, low-drag bombs was introduced, designed for external carriage by fighter-bomber aircraft rather than in internal bays. They come in only two sizes, and . Both bombs have a single nose fuze. Both the 54 and 62 series designs remain in use. The most common of these are the FAB-100, FAB-250, FAB-500, FAB-750, and FAB-1500, roughly corresponding to the U.S. Mark 80 series. These have seen widespread service in Russia, Warsaw Pact nations, and various export countries. Larger bombs with less streamlined shapes also remained in the Soviet arsenal, primarily