At the beginning of the 1990s, the Soviet Union/Russia performed flight tests on the Progress D-236, a geared contra-rotating propfan engine based on the core of the Progress D-36 turbofan, with eight blades on the front propeller and six blades on the back propeller. One testbed was a 10,100 hp (7,500 kW) propfan mounted to an Ilyushin Il-76 and flown to the Hannover ILA 90 airshow, which was intended for an unidentified four-propfan aircraft.[46] The D-236 flew 36 times for a total of 70 flight test hours on the Il-76.[47] The other testbed was a 10,990 hp (8,195 kW), 14 ft unit (4.2 m; 170 in; 420 cm) mounted to a Yakovlev Yak-42E-LL and flown to the 1991 Paris Air Show, as a demonstration for the planned Yak-46 aircraft with twin propfan engines,[48] which in its base 150-seat version would have a range of 1,900 nmi (2,200 mi; 3,500 km) and cruise at a speed of 460 kn (530 mph; 850 km/h; 780 ft/s; 240 m/s)[49] (Mach 0.75).[50] The Soviets claimed the D-236 had a true aerodynamic efficiency of 28 percent and a fuel savings of 30 percent over an equivalent turboprop.