It was in 2007 that US-based Honeywell successfully demonstrated to the Indian Air Force (IAF) the ‘drop-in installation’ of its F125IN turbofan on a Jaguar IS interdictor/strike aircraft. The F125IN delivers 30% higher thrust (27.7kN of dry thrust and 43.8kN with afterburning) than the Jaguar IS’ existing Rolls-Royce-Turbomeca Adour Mk.811 turbofan (rated at 25kN dry thrust and 37.5kN with afterburning), apart from offering improved pilot safety, lower maintenance costs and outstanding reliability. The turbofan’s modular construction and its integral dual full-authority digital engine control (FADEC) system can provide substantial savings (Rs.7,000 crore or US$1.5 billion) to the operator’s in life-cycle costs. Its time-between-overhauls (TBO) is 2,000 hours and its total technical service life (TTSL) of 4,000 hours, compared to the Adour Mk.811’s 1,200 hours and 2,400 hours.
In June 2009 Rolls-Royce successfully installed and tested the Adour Mk.821 turbofan (an uprated and upgraded derivative of the Mk.811) in a Jaguar IS to prove its capability and suitability to the IAF. However, the Mk.821 with a TBO of 2,000 hours and TTSL of 4,000 hours was being offered as a ‘low-cost’ upgrade and was thus bereft of some of the more advanced features found on the F125N.
An RFP for new turbofans with higher thrust was issued by India’s Ministry of Defence ( MoD) on November 26, 2010, to two turbofan manufacturers—Rolls-Royce and Honeywell. The RFP had specified a requirement for 200 turbofans estimated to cost around Rs.3,000 crore ($670 million) Rolls-Royce later opted to withdraw from the competitive evaluations rather than be eliminated, resulting in a “single vendor situation”.
It was at this time that the MoD-owned Hindustan Aeronautics Ltd (HAL) decided to use its internal resources with the aim of producing an indigenously designed and developed non-afterburning turbofan within a timeframe of six years beginning from 2013. Designated as the HTFE-25 and rated at 25kN dry thrust, its engine core’s inaugural run was successfully completed in the presence of the then Defence Minister Manohar Parrikar at HAL’s Engine Division on December 14, 2015. Only two such engine cores had been built by then and even at that time no mention was made of this turbofan being developed for the Jaguar IS.
It was only in March 2019 that HAL decided to develop an afterburner for the HTFE-25 for giving it a maximum thrust of 40.39kN. However, HAL has not yet officially stated whether or not it will offer this variant of the HTFE-25 for the IAF’s Jaguar IS, about 80 of which are due to be re-engined. Nor has HAL provided any data on what will be the TBO and TTSL of an HTFE-25 turbofan fitted with an afterburner. It also remains unclear whether HAL will eventually be forced to seek technical consultancy expertise from the likes of Rolls-Royce for coming up with an optimally engineered production-series HTFE-25 turbofan meant for the Jaguar IS.
