distance. The nose housed the armament of one Nudelman N-37 autocannon and two Nudelman-Suranov NS-23 autocannon. The N-37 could be replaced by a Nudelman-Suranov NS-45. The aircraft carried 100 rounds for each NS-23 and 40 rounds for the N-37. Two FAB-250 high explosive bombs could be carried underneath the forward fuselage, but the N-37 had to be dismounted to do so. As the TR-1 engines originally intended for the Su-9 were not yet ready for flight testing in late 1945, Pavel Sukhoi suggested substituting a pair of Jumo 004 engines and this was approved on 15 December. The full-scale mockup was found to be acceptable on 16 February 1946 and the Council of People's Commissars issued an order on 26 February that the manufacturer's flight testing was to begin on 1 November. This goal was not met because the OKB was heavily committed to other projects like the trainer version of the Tupolev Tu-2 bomber, inexperience with JATO units, and late delivery of RD-10 engines. The first prototype was completed in mid-October and made its first flight on 13 November. The test pilots found the aircraft easy to fly, but the control forces were very high at speed and it lacked enough directional stability. Enlarging the vertical stabilizer cured this last problem and hydraulic boosters were fitted for the control system. The aircraft was revealed to the general public on 3 August 1947 at a flypast at Moscow's Tushino Airfield and the aircraft began its state acceptance trials three days later. Flight testing was completed by 25 May 1948 after 136 flights had been completed. It demonstrated a top speed of at an altitude of and an endurance of one hour and 44 minutes. It had very docile handling qualities with one engine inoperative. The aircraft was recommended for production, but it was significantly slower than the Mikoyan-Gurevich MiG-9 and Yakovlev Yak-15. The government declined to do so and the program was terminated. A two-seat trainer version, the Su-9UT, was planned during 1946, but it too was cancelled. The cockpit for the student would have been positioned ahead of the instructor's cockpit and each would have had a separate canopy. The armament would have been reduced to a pair of Berezin B-20 autocannon, each with a hundred rounds of ammunition. The armor would have been removed to save weight. Su-11 Another prototype was begun in 1946, but this aircraft was