US firm Honeywell has overcome supply chain bottlenecks and delivered the first batch of engines for the overdue indigenous basic trainer aircraft—critical for the Indian Air Force—to Bengaluru-based Hindustan Aeronautics Limited (HAL), officials aware of the matter said on Wednesday.India’s delayed trainer aircraft gets critical engine boostHoneywell has delivered three TPE331-12B turboprop engines for the HTT-40 (Hindustan Turbo Trainer-40) aircraft being built at HAL, and assured the state-run firm of timely supplies, the officials said, asking not to be named.“HAL aims to fast-track aircraft deliveries as engine supplies stabilise,” one of the officials said. The platform will serve as a stepping stone for pilots to develop critical flying skills.The air force ordered 70 basic trainers for ₹6,838 crore three years ago to train its rookie pilots. Under the contract, HAL was supposed to supply 12 aircraft to the IAF in fiscal 2025-26, but it has not delivered a single plane yet because engines were unavailable.Under a $100-million contract signed almost four years ago for supplying and manufacturing 88 TPE331-12B engines/kits, Honeywell was supposed to deliver the first engine in September 2025. The US firm will supply 16 units and HAL will build the rest through technology transfer.The remaining engines are expected at the rate of two per month, said another official. Two series production HTT-40s are already flying with ‘Category B’ (used) TPE331-12B engines that powered the prototype aircraft.A new manufacturing facility for the HTT-40s will help accelerate deliveries. Last October, defence minister Rajnath Singh inaugurated production lines for the LCA Mk-1 and the HTT-40 basic trainer in Nashik to meet the air force’s growing needs. HAL is now capable of producing 20 HTT-40s a year at its factories in Bengaluru and Nashik.The tandem-seat HTT-40 has an air-conditioned cockpit, modern avionics, hot refueling capability (refuelling with the engine running on the ground), and zero-zero ejection seats (for safe ejection at low speeds and low heights). The HTT-40 currently has 56% local content, which will progressively increase to over 60% through further indigenisation of major components and subsystems.Currently, ab initio (Stage-I) flying training for all rookie pilots is carried out on Swiss-origin Pilatus PC-7 MkII basic trainers. Stage-I training is common for all pilots after which trifurcation into fighter, transport and helicopter streams takes place.Those selected for the fighter stream proceed to Stage-II training on PC-7 MkII and Kiran Mk-1A jet trainers and then Stage-III on the British-origin Hawk advanced jet trainers before they can fly supersonic fighter planes. Pilots from the other two streams carry out their Stage II and III training on different types of transport aircraft and helicopters.Plans to buy more Pilatus PC-7 MkII trainers were hit in July 2019 after the defence ministry suspended business dealings with Pilatus Aircraft Limited for one year for violating a pre-contract integrity pact in a ₹2,900-crore deal for 75 basic trainers, and also factoring in Indian investigations against the firm for alleged corruption and irregularities. The contract with Pilatus included a clause for follow-on purchase of 38 more planes.