from the Tu-95. The NK-12 engine powers another well-known Soviet aircraft, the Antonov An-22 Antheus, a heavy-lift cargo aircraft. At the time of its introduction, the An-22 was the largest aircraft in the world and is still by far the world's largest turboprop-powered aircraft. From the 1960s through the 1970s, it set several world records in the categories of maximum payload-to-height ratio and maximum payload lifted to altitude. Of lesser note is the use of the NK-12 engine in the A-90 Orlyonok, a mid-size Soviet ekranoplan. The A-90 uses one NK-12 engine mounted at the top of its T-tail, along with two turbofans installed in the nose. In the 1980s, Kuznetsov continued to develop powerful contra-rotating engines. The NK-110, which was tested in the late 1980s, had a contra-rotating propeller configuration with four blades in front and four in back, like the NK-12. Its was smaller than the NK-12's diameter, but it produced a power output of , delivering a takeoff thrust of . Even more powerful was the NK-62, which was in development throughout most of the decade. The NK-62 had an identical propeller diameter and blade configuration to the NK-110, but it offered a higher takeoff thrust of . The associated NK-62M had a takeoff thrust of , and it could deliver of emergency thrust. Unlike the NK-12, however, these later engines were not adopted by any of the aircraft design bureaus. In 1994, Antonov produced the An-70, a heavy transport aircraft. It is powered by four Progress D-27 propfan engines driving contra-rotating propellers. The characteristics of the D-27 engine and its propeller make it a propfan, a hybrid between a turbofan engine and a turboprop engine. United States The United States worked with several prototypes, including the Northrop XB-35, XB-42 Mixmaster, the Douglas XTB2D Skypirate, the Curtiss XBTC, the A2J Super Savage, the Boeing XF8B, the XP-56 Black Bullet, the Fisher P-75 Eagle and the tail-sitting Convair XFY "Pogo" and Lockheed XFV "Salmon" VTOL fighters and the Hughes XF-11 reconnaissance plane. The Convair R3Y Tradewind flying boat entered service with contra-rotating propellers. However, both piston-engined and turboprop-powered propeller-driven aircraft were reaching their zenith and new technological developments such as the advent of the pure turbojet and turbofan engines, both without propellers, meant that the designs were quickly eclipsed. The US propeller manufacturer, Hamilton Standard, bought a Fairey Gannet in 1983 to study the effects of counter rotation