Bengaluru: The indigenous Intermediate Jet Trainer designed and developed by the Hindustan Aeronautics Limited to replace the ageing Kiran aircraft fleet of the IAF commenced spin flight testing in Bengaluru.

The spin testing of an aircraft is the most crucial phase of its flight testing.

In a statement, HAL said: "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."

"For 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 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. Post modification, 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 (Anti-Spin Parachute Systems). 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."

The state-owned firm’s programme to develop a basic HTT-40 trainer is nearly six years behind schedule. The IAF is currently running low on trainers with plans to procure more aircraft hitting a dead end.

The IAF expects to start receiving the trainer in 2022 and complete deliveries of 70 aircraft in four years.