The test pilots found the aircraft easy to fly, but the control forces were very high at speed and it lacked enough directional stability.
The first prototype was completed in mid-October and made its first flight on 13 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 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. Two 250-kilogram FAB-250 high explosive bombs could be carried underneath the forward fuselage, but the N-37 had to be dismounted to do so.Īs 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 aircraft carried 100 rounds for each NS-23 and 40 rounds for the N-37. The N-37 could be replaced by a 45-millimeter Nudelman N-45. The nose housed the armament of one 37-millimeter Nudelman N-37 autocannon and two 23-millimeter Nudelman-Suranov NS-23 autocannon.