The Hindustan Aeronautics Ltd (HAL) subsonic Intermediate Jet Trainer or the HAL HJT-36 Sitara project (Hindustan Jet Trainer) is back to testing after a redesign. HJT-36 was designed and developed by the HAL to replace the ageing HAL HJT-16 Kiran MK II aircraft fleet currently with the Indian Air Force IAF). HJT-36 has commenced spin flight testing in Bengaluru and the flight was piloted by HAL’s test pilots Gp. Capt H.V. Thakur (Retd) and Wg. Cdr P. Avasti (Retd).
“The spin testing of an aircraft is the most crucial phase of its flight testing. Accordingly, the testing will be gradually progressed to assess the behaviour of the aircraft till six turn spins to either side to meet the targeted requirement,” stares the HAL release.
HAL release states that the IJT has already been tested to its full envelope in terms of speed, altitude and load factor (‘G’ envelope) and has also been integrated with drop tanks as well as bombs. For the spin test, HAL redesigned the aircraft by moving the vertical tail aft and extending the rudder surface. These changes for ensuring a satisfactory spin behaviour required an extensive redesign of the rear fuselage and the rudder. The changes have been incorporated in two aircraft with the involvement and clearance from certification agencies at every stage. Postmodification, the two aircraft underwent significant flight tests to assess the general handling with the new configuration of fin and rudder.
These aircraft have now been incorporated with the necessary safety devices including an Anti-Spin Parachute System. During the first flight, initially, the aircraft was taken through one turn spin to the left and right-hand sides to test the spin characteristics.
HAL HJT-36 Sitara was sent back to the drawing boards after it was clear that the aircraft had difficulties during the spin test. Although rarely required for civilian flights, the stall, spin and recovery training is a crucial skill to be imparted to the combat flight trainees. The Intermediate Jet Trainer is meant for stage II of IAF pilot training.