The fuselage was conventional with a mid-mounted wing with 35 degrees of sweep, an angle that ensured that the main wing spar passed through the fuselage in front of the bomb bay. Retractable tricycle landing gear was fitted, with all three gear strut units retracting rearwards, with the main gear units retracting rearwards into extensions of the inner engine nacelles. The Tu-95/I, with 2TV-2F engines, first flew in November 1952 with test pilot Alexey Perelet at the controls. After six months of test flights this aircraft suffered a propeller gearbox failure and crashed, killing Perelet. The second aircraft, Tu-95/II, used four 12,000 eshp Kuznetsov NK-12 turboprops which proved more reliable than the coupled 2TV-2F. After a successful flight testing phase, series production of the Tu-95 started in January 1956. For a long time, the Tu-95 was known to U.S./NATO intelligence as the Tu-20. While this was the original Soviet Air Force designation for the aircraft, by the time it was being supplied to operational units it was already better known under the Tu-95 designation used internally by Tupolev, and the Tu-20 designation quickly fell out of use in the USSR. Since the Tu-20 designation was used on many documents acquired by U.S. intelligence agents, the name continued to be used outside the Soviet Union. Initially, the United States Department of Defense evaluated the Tu-95 as having a maximum speed of with a range of . These numbers had to be revised upward numerous times. Like its American counterpart, the B-52, the Tu-95 has continued to operate in the Russian Air Force while several subsequent iterations of bomber design have come and gone. Part of the reason for this longevity was its suitability, like the B-52, for modification to different missions. Whereas the Tu-95 was originally intended to drop free-falling nuclear weapons, it was subsequently modified to perform a wide range of roles, such as the deployment of cruise missiles, maritime patrol (Tu-142), and even civilian airliner (Tu-114). An AWACS platform (Tu-126) was developed from the Tu-114. An icon of the Cold War, the Tu-95 has served not only as a weapons platform but as a symbol of Soviet and later Russian national prestige. Russia's air force has received the first examples of a number of modernised strategic bombers in Tu-95MSs following upgrade work. Enhancements have been confined to the bomber's electronic weapons and targeting systems. Modernization of the first batch