Kaveri turbofan programme seeks extension

By SP's Special Correspondent

February 17, 2012: The Kaveri turbofan engine programme has asked the government for an extension and more funds to overcome a fresh set of technological hurdles that have cropped up in the latest phase of flight tests. According to top sources, the extension involves at least 120 hours of additional flight testing. Interestingly, while the Kaveri is currently being flight-tested on a specially kitted out Ilyushin-76 engine test bed aircraft at the Gromov institute in Russia, the Kaveri extension programme envisages flight testing on a modified Tejas airframe, or similar aircraft. An official familiar with the extension proposal says one of the early prototype vehicles of the Tejas, which haven't been flying for years, could be modified to fly with the Kaveri engine.

As things stand, the Kaveri has completed close to 60 hours of flight-testing at the Gromov institute, the highlight of which was the use of a fully indigenous FADEC. However, the flight testing phase has also accentuated the engine's fundamental problems that have kept it in development for so long. Adding to a littany of woes, compounded by overall insufficient performance parameters, are problems in the turbine and fan assemblies, possibly structural issues as well. The IAF and Navy don't want to fly with an engine that puts out anything less than 90kN with reheat at sea-level — the Kaveri falls well short of that figure, and is the principle reason why the IAF and Navy have both gone in for GE engines on all foreseeable deliveries of the Tejas Mk.1 and Mk.2.

The IAF, predictably, is not happy with progress. An Air Commodore associated with liaison work on the Kaveri programme says, "The problem is no longer about delays and delivery, but about performance. The Kaveri engine in its present form cannot power fighter jets with modern performance requirements. It can be perhaps modified for other uses, but for fast jet performance, the Kaveri in its present form can be ruled out."

There have also been unforeseen delays in the joint engine effort by DRDO and Snecma for a robust 90kN turbofan engine, based on the M88 ECO core and meeting the minimum performance requirements of the IAF and Navy. Negotiations on technology sharing and intellectual property have taken the better part of the two years, though a top official confirmed that a contract between DRDO and Snecma is likely to be signed within the year. The joint effort, in effect, calls an end to the Kaveri K9 programme as it stands. What it does is propose to quickly build a 90kN thrust turbofan and offer it off the block to the IAF and Navy for their Tejas Mk.1s. The Kaveri-Snecma engine, in twin configuration, could also power India's advanced medium combat aircraft (AMCA), though that is still well into the future.

DRDO sources confirm that Snecma will transfer several key technologies as part of the joint engine programme, which include single crystal blades, bladed disk and EBPVD (electron beam plasma vapour deposit coating), all critical areas that the Kaveri engine has failed to find solutions to within the country, though not for lack of trying. Programme managers believe single crystal blade technology will be a major solution to one of the Kaveri's biggest problems — deformation of blades during testing as a result of high ambient temperatures. This has proved to be a severe limiting factor, considering that structurally solidified blades have structural integrity that comes nowhere close to single crystal structures. According to sources, it is negotiations over the modalities for single crystal blade technology that has taken so long, though the end is finally in sight. Several DRDO labs and the MDNL have tried for years to create an indigenous SCT solution, but so far without success.

The tie up with Snecma will launch the Gas Turbine Research Establishment (GTRE) into an all-new league, and will involve modern forging, welding and casting techniques for the first time. Unlike the Kaveri K9 programme, the K10 programme (the official designation for the proposed effort with Snecma) will be professionally monitored from the outset, with hard timelines and investments. The work share model has been hammered down, and scientists are confident that they have extracted a competitive contract from the French. Initial reservations about sharing certain technologies were ironed out following the slew of military contracts that went France's way, the last being the substantive Mirage 2000 H/TH upgrade programme.

Almost the entire work force that has been dedicated so far to the Kaveri will be diverted to the K10 effort with Snecma. Scientists foresee challenges in absorbing the technology, but are confident that they will achieve goals once the contract is signed and the effort flagged off. A senior GTRE scientist says, "We have the will and the base technologies. We understand fully well what our shortcomings are, and are eager to deliver a full performance engine to the customer. Gone is the time when we can stay in the lab indefinitely saying we will come up with certain technologies by ourselves. The French will help us cut down on development time. And we will both deliver an engine that will power Indian aircraft. Everybody wins."