Yakovlev Yak - 23 The Yakovlev Yak - 23 ( in Russian Як - 23 , USAF / DoD reporting name " Type 28 " ) , NATO reporting name " Flora " was a jet fighter developed in the USSR in the 1940s and used in early 1950s . Design and development . The Yak - 23 was developed as a simple lightweight jet fighter , on Yakovlev ' s own initiative . It was a development of the earlier Yak - 15 and Yak - 17 fighters , retaining their non - conventional layout with a jet engine in the fuselage nose and exhaust under the cockpit , but the construction was all new . Its wings were derived from the Yak - 19 . The Yak - 23 used a Soviet copy of the British Rolls - Royce Derwent V turbojet engine , produced as the Klimov RD - 500 . It first flew on July 8 , 1947 . After successful flights , it underwent state trials in 1948 and was accepted for series production . It was evaluated as highly maneuverable , with a good acceleration and take - off and climb capabilities thanks to high thrust - to - weight ratio . Faults were poor directional stability at speeds around Mach 0 . 86 and lack of cockpit pressurization . Despite being one of the best straight - wing jet fighters , it was inferior to new swept - wing designs . Operational history . The first aircraft were produced in a factory in Tbilisi in October 1949 . In late 1949 they entered Soviet air force service , and were also ordered for export in 1949 - 50 . The Yak - 23 was quickly replaced in the Soviet service with the more complicated swept - wing MiG - 15 , which offered superior performance . In all , only 310 Yak - 23 aircraft were built before production ended in 1950 . Apart from the fighter there were two trainer versions of the Yak - 23 which were built in small numbers . The Yak - 23UTI two - seat trainer which appears to have had the unusual arrangement of having the instructor sat in front of the student , and the Yak - 23DC trainer which was produced in Rumania . Small numbers of Yak - 23 were exported to Czechoslovakia ( 20 from 1949 , named S - 101 ) , Bulgaria ( from 1949 ) , Poland ( about 100 , from 1950 ) , Romania ( 62 , from 1951 ) and probably Albania . Poland and Czechoslovakia acquired license of Yak - 23 , but didn ' t start production in favour of the MiG - 15 . Yak - 23s were withdrawn by the late 1950s . They were not used in combat ( there are reports of US pilots encountering Yak - 23s during the Korean War , but their presence in North Korea is not confirmed ) . US testing . A single Yak - 23 was acquired by US intelligence , via Yugoslavia , in November 1953 . It was a Romanian Yak - 23 flown by Mihail Diaconu who defected with it . The aircraft arrived disassembled , and was shipped to the Air Force Test and Evaluation Center at Wright Field near Dayton , Ohio . It was reassembled and made operational for several flight tests , during which time it was disguised with U . S . markings . Efforts were made to keep the aircraft ' s identity secret , and it was only flown in the early morning . On one occasion it was passed on the runway by a formation of F - 86 ' s , whose pilots inquired as to the plane ' s identity . A story was conceived that the aircraft was a Bell X - 5 , which had a similar layout . At the completion of design and flight evaluations the aircraft was again disassembled and shipped quietly back to Yugoslavia in its original paint scheme . Records . On September 21 , 1957 , the Polish pilot Andrzej Abłamowicz set two FAI world records on Yak - 23 with civilian markings SP - GLK , in its weight class , climbing at 3 , 000 m ( 9 , 843 ft ) in 119 seconds ( 4 , 962 . 6 ft / min ) and at 6 , 000 m ( 19 , 685 ft ) in 197 seconds ( 5 , 995 . 4 ft / min ) . This plane was withdrawn in 1961 , being possibly the last Yak - 23 used in the world .