an external load of 4,000 kg (8,818 lb). In 1957, the improved model Yak-24U was developed, rebuilt from serial helicopter, with all-metal rotors of larger diameter (21 m/69 ft) and an all-metal wider fuselage. It could carry 40 soldiers or 3,500 kg (7,716 lb) of cargo, including ASU-57 tank destroyer. It completed test program in 1958, but did not enter production. A civilian variant for Aeroflot for 30 passengers was the Yak-24A of 1960, but it was not produced either. There were two proposed models: the Yak-24K nine-seat VIP salon with a shorter fuselage and the civilian Yak-24P for 39 passengers with more powerful 2,013 kW (2,700 hp) turboshaft engines, but neither reached production. The helicopter was little known, so specifications and technical details varied among different sources, and also older publications claimed, that Yak-24U and passenger Yak-24A were produced. Data on the Yak-24 is inconsistent and sometimes contradictory, the exact number of helicopters produced is unknown, with estimates ranging from 40 to 100 units depending on the source of the data. According to newer Russian sources, only 35 series helicopters were built in 1956–1958 in Leningrad, in addition to two prototypes and three pre-series helicopters (1953-1958). All sources agree that production of the Yak-24 was curtailed due to technical problems, and the need for a heavy transport helicopter was fulfilled by the successful Mil Mi-6. According to some sources, the passenger Yak-24A for Aeroflot was not actually produced. The exact date of the Yak-24's decommissioning from the Soviet Air Force, and possibly Aeroflot, is unknown. A surviving Yak-24 is preserved at the Central Air Force Museum in Monino, Russia. Operators Soviet Air Force Specifications (Yak-24U) See also References Military helicopters 1950s Soviet military transport aircraft Yak-024 Tandem rotor helicopters 1950s Soviet helicopters Twin-engined piston helicopters Aircraft first flown in 1952