Turboprop engine

Every military turboprop engine flying an Indian platform is imported. As of 2026, the HTT-40 trainer, the Dornier 228, and the prototypes planned for India's high-altitude UAVs all run on foreign cores — Honeywell TPE331 and Pratt & Whitney PT6 variants. On this one class of engine, the indigenous share is zero.

A turboprop is, at its heart, a turboshaft engine driving a propeller through a reduction gearbox. That makes it sound modular, but the hard parts are unforgiving: a multi-stage compressor that must hold its pressure ratio, turbine blades cast as single crystals to survive combustion heat, and a variable-pitch propeller governed to the right blade angle across the flight envelope. Only six nations design and build these engines — the United States, United Kingdom, France, Canada, Russia and Germany. The dominance of a handful of designs is stark: Pratt & Whitney Canada's PT6 alone has passed 64,000 units and 500 million flight hours across more than 155 aircraft types.

India's position is best described as emerging. Hindustan Aeronautics Limited's engine division at Koraput is developing the HTSE-1200, a 1,200-kilowatt turboshaft. Its core reached 100 percent RPM and completed sea-level trials; five prototype engines were under fabrication as of September 2024, with delivery scheduled for mid-2025. On the HTT-40 programme, Honeywell supplies the first 16 TPE331-12B engines from the United States, after which HAL assembles the remaining 72-plus and builds in-country repair and overhaul capacity.

The turboprop-specific push is still on paper. The Aeronautical Development Establishment issued an Expression of Interest in September 2025 for turboprop engines of 900–1,500 shaft horsepower to power a HALE UAV, followed by a development-cum-production partner EoI in December 2025. Early prototypes will fly on imported Honeywell TPE331-10 engines. The indigenous route under study is adapting the HTSE-1200 turboshaft core into a turboprop variant with a private-sector partner.

The gap is structural and named plainly by GTRE's own director: India has invested significantly less in aircraft engine technology than the United States, Russia, Europe and China. The Kaveri turbofan programme cost about $239 million; comparable Western engines cost $1.6 billion and more.

What it would take is visible in the dependency chain. The demonstrated pieces exist — single-crystal blade casting achieved through DMRL in 2021, near-isothermal forging, a certification pathway. The unfinished work sits in high-pressure compressors, superalloy forgings and engine control software, and in the sustained funding to carry a turboshaft core through to a certified, series-produced turboprop.