the belly carried testing instruments, mistook it for a large ventral radar for a mixed interceptor/AWACS role. The production version lacked the bulge and had a large nose radome housing a radar, known as RP-S Smerch, having a detection range of about 50 km (31 mi) and a lock-on range of about 40 km (25 mi). Armament of the Tu-128 was four Bisnovat R-4 air-to-air missiles (known as K-80 during development; NATO reporting name AA-5 'Ash'). Usually two of them were R-4Rs with semi-active radar homing and two were R-4T infrared-homing missiles, with the former on the outer pylons and the latter on the inner underwing pylons. There was no internal weapons bay. Production of the Tu-128 ended in 1970 with a total of 198 aircraft having been built. Development of various projects designated Tu-28A, Tu-28-80, Tu-28-100, Tu-138, and Tu-148 were proposed by the Tupolev Design Bureau but all were abandoned. Operational history The Tu-128's only publicly reported combat operation was the destruction of NATO reconnaissance balloons. The aircraft remained in service until 1990. Through the 1980s, units armed with the Tu-128 converted to the Mikoyan MiG-31, which features more advanced sensors and weapons. Variants Prototype of Tu-28 ('Fiddler-A') Development test aircraft, one built. OKB designation was 128. In the West, Fiddler-A was used for all the aircraft with twin ventral fins — these included a prototype and a few of initial production (perhaps two planes). Tu-128 (also known as Tu-28; 'Fiddler-B') Main version, first deployed operationally in 1964 (or 1966 – sources differ). The military designation was at first Tu-28, but the existing aircraft were renamed in 1963. The entire weapon complex (aircraft, radar, missiles) was designated Tu-128S-4. In the Western sources, but not in Soviet, often the more precise, but erroneous, designation of this version is mentioned as either Tu-28P or Tu-128P. Tu-128UT (also known as Tu-28UT) Training version with an additional cockpit forward of the normal one, in place of a radar. Ten built and four converted from standard interceptors. Tu-128M A 1979 modernization of almost all existing aircraft for better interception at low altitude. Development originated in 1970. Engines and airframe were not altered. The full designation of the entire weapons complex was Tu-128S-4M. It contained a new RP-SM Smerch-M radar, and new missile set: R-4RM plus R-4TM. Abandoned Tu-28A New development, abandoned. Tu-28-80 Development designation, abandoned. Tu-28-100 Development designation, abandoned. Tu-138 New development, abandoned. Tu-148