The HTT-40 has completed spin tests to the left and right — a manoeuvre in which the aircraft is deliberately thrown into a dangerous uncontrolled spin and then recovered safely into level flight

In flight-testing on 7th September in Bangalore, HAL’s test pilots threw the HTT-40 into multiple spins and, each time, the trainer returned to level flight smoothly. In so doing, the HTT-40 cleared the so-called “Six-Turn Spin Test”, regarded as the ultimate and most difficult test for a trainer aircraft.

A few more tests are due to follow before the aircraft can get its operational certification, likely in end-2019, according to a person familiar with the program.

HAL said it expected production clearance for the HTT-40 by the end of this year. The Defence Acquisition Council has approved buying of 70 HAL-built basic trainers for the Indian Air Force. The HTT-40, when acquired, will join the 75 Swiss Pilatus PC-7 Mark II trainers that are already in service.

The successful start of the spin testing gives a boost to HAL and also restores its credibility in successfully designing a spin-worthy aircraft.

The spin test is the most crucial phase in developing a safe and airworthy aircraft, according to HAL. Novice military pilots begin their flying careers with a basic trainer and then graduate on to fighters and transport planes.

“This is a big boost [for the team]. We got the spin right after two generations, the last was in the 1980s for the Kiran,” said the official associated with trainer development.

A statement said, “HTT-40 began the most awaited phase of the ‘spin test’ by successfully entering into a multiple-turn spin and subsequently recovering with the appropriate controls.”

Gp Capt KK Venugopal in front, and Gp Capt Subroto Chaki in the rear seat. Spin recovery parachute gantry (yellow structure) attached to rear fuselage - Image Courtesy: Angad Singh

“From the right-hand spin on 7th September to completion of spin trials with today’s left-hand spins, required 30 test flights. That’s both very few flights in total, yet also a staggering effort over just three weeks,” tweeted aviation analyst, author and photographer Angad Singh.

According Mr. Arup Chatterjee, Director (Engg and R&D) the PSQR test points have been met and the spin completion is the last metric which needs to be accomplished before the aircraft enters service. As a matter of fact, HTT 40 exceeds the Preliminary Services Qualitative Requirements (PSQR) on most fronts and offers a technologically advanced product than its competitor.

HTT-40, too, had been earlier rejected by the IAF which opted for the imported Pilatus.

The HTT-40 has already met and, in many aspects of flight performance, surpassed the “Air Staff Qualitative Requirements” (ASQRs), which lists out the flight performance — speed, turn, ceiling, etc. — that the IAF demands from an aircraft.

Our Bureau