The HTT 40 (Basic Trainer Aircraft) designed and developed by state-owned aviation major, Hindustan Aeronautics Limited (HAL), has commenced the much-awaited 'spin test' phase.

The aircraft successfully entered into two-turn spin and subsequently recovered with appropriate controls. Two test pilots undertook the first-ever spin entry testing at around 1.30 pm on Friday, an official statement from HAL said.

The aircraft was piloted by Gp Capt (Retd) K K Venugopal, DGM-test pilot (FW), from the front cockpit and Gp Capt S Chaki (retd), senior test pilot (FW), from the rear. The stall testing was already completed and the project galloped its way to spin tests.

HAL chairman and managing director R Madhavan said the spin test start restored HAL's credibility in successfully designing a spin-worthy aircraft.

Spin-testing is a critical aspect of flight-testing in any aircraft development programme. HAL’s aircraft research and design centre (ARDC) had conducted extensive wind-tunnel testing and mathematical model analyses to arrive at the spin chacteristics of the aircraft. The entire study is put to test during those first few moments of spin testing.

Arup Chatterjee, director (engg and R&D) said the preliminary services qualitative requirements (PSQR) test points have been met and the spin completion is the last metric which needs to be accomplished before the aircraft enters service.

The detailed design of the project started in August 2013 with internal funding and made its way to the spin tests in five years. The Defence Acquisition Council (DAC) has approved procurement of 70 Basic Trainer Aircraft from HAL. The production clearance for the aircraft is expected by the end of 2018.

HTT-40 had recorded its maiden flight on May 31, 2016, which lasted for about 30 minutes. The aircraft's first public introduction flight was on June 17, 2016, witnessed by the then Defence Minister Manohar Parrikar at the HAL airport. Its second prototype completed the maiden flight on May 19, 2017.