is somewhat offset by its mechanical complexity and the added weight of this gearing that makes the aircraft heavier, thus some performance is sacrificed to carry it. Nonetheless, coaxial contra-rotating propellers and rotors have been used in several military aircraft, such as the Tupolev Tu-95 "Bear". They are also being examined for use in airliners. Use in aircraft While several nations experimented with contra-rotating propellers in aircraft, only the United Kingdom and Soviet Union produced them in large numbers. The first aircraft to be fitted with a contra-rotating propeller to fly was in the US when two inventors from Ft Worth, Texas tested the concept on an aircraft. United Kingdom A contra-rotating propeller was patented by F. W. Lanchester in 1907. Some of the more successful British aircraft with contra-rotating propellers are the Avro Shackleton, powered by the Rolls-Royce Griffon engine, and the Fairey Gannet, which used the Double Mamba Mk.101 engine. In the Double Mamba two separate power sections drove one propeller each, allowing one power section (engine) to be shut down in flight, increasing endurance. Another naval aircraft, the Westland Wyvern had contra-rotating propellers. The Martin-Baker MB 5 test aircraft also used this propeller type. Later variants of the Supermarine Spitfire and Seafire used the Griffon with contra-rotating props. In the Spitfire/Seafire and Shackleton's case the primary reason for using contra-rotating propellers was to increase the propeller blade-area, and hence absorb greater engine power, within a propeller diameter limited by the height of the aircraft's undercarriage. The Short Sturgeon used two Merlin 140s with contra-rotating propellers. The Bristol Brabazon prototype airliner used eight Bristol Centaurus engines driving four pairs of contra-rotating propellers, each engine driving a single propeller. The post-war SARO Princess prototype flying boat airliner also had eight of its ten engines driving contra-rotating propellers. USSR, Russia and Ukraine In the 1950s, the Soviet Union's Kuznetsov Design Bureau developed the NK-12 turboprop. It drives an eight-blade contra-rotating propeller and, at , it is the most powerful turboprop in service. Four NK-12 engines power the Tupolev Tu-95 Bear, the only turboprop bomber to enter service, as well as one of the fastest propeller-driven aircraft. The Tu-114, an airliner derivative of the Tu-95, holds the world speed record for propeller aircraft. The Tu-95 was also the first Soviet bomber to have intercontinental range. The Tu-126 AEW aircraft and Tu-142 maritime patrol aircraft are two more NK-12 powered designs derived