Kaveri engine to fly futuristic unmanned aircraft

The Kaveri undergoes testing at the GTRE

By Ajai Shukla

Gas Turbine Research Establishment (GTRE), Bangalore

Business Standard, 26th Dec 12

The Defence R&D Organisation’s (DRDO’s) faltering project to develop an indigenous jet engine has sparked into life again. With the Kaveri engine, born from this project, found short on power for the Tejas Light Combat Aircraft (LCA), the MoD has nominated the Kaveri to power the hush-hush Unmanned Strike Air Vehicle (USAV), a pilot-less bomber aircraft that the DRDO is developing.

The veil of secrecy surrounding the USAV project was thrown off on Dec 10, when the defence minister told parliament that, “(The) Kaveri spin-off engine can be used as propulsion system for (the) Indian Unmanned Strike Air Vehicle.”

Already drones, or unmanned air vehicles (UAVs), are changing the nature of air power with their ability to strike targets without endangering pilots lives. USAVs are bigger, 8-10 tonne drones, akin to strike fighters in their ability to carry heavy weaponry including bombs, rockets and missiles. Since they are piloted by remote control, they can be built lighter, stealthier, and sent on even the most risky missions.

The Indian USAV project is a lease of life for the Kaveri engine. Although India will import jet engines worth Rs 1,60,000 crore over the next decade (DRDO projections) none of these can be used for the USAV. The Missile Technology Control Regime (MTCR) prohibits its 34 signatories --- including every major engine manufacturing country --- from selling engines for unmanned systems with ranges of over 300 kilometres.

An Indian jet engine, therefore, must power the USAV and the Kaveri is the only option. Although underpowered for fast-moving fighter aircraft, the DRDO believes the Kaveri is well suited for the USAV, which is lighter, flies slower and manoeuvres less sharply. 

Business Standard visited the Gas Turbine Research Establishment (GTRE), the DRDO laboratory that is developing the Kaveri engine. It reached a key landmark last year, when a prototype Kaveri was flight-tested in Russia at the Gromov Flight Research Institute (GFRI). The engine’s performance was measured on a “flying test-bed”, a four-engine IL-76 transport aircraft that had one of its original engines replaced with a Kaveri.

During this test the Kaveri did well, generating 49.2 KiloNewtons (KN) of “dry thrust”, marginally less than its target of 51 KN. But there was a serious shortfall in “wet thrust”; the Kaveri generated just 70.4 KN, well short of the targeted 81 KN.

[“Dry thrust” refers to the standard output of an engine in routine flight. “Wet thrust” refers to the enhanced output that is generated when the fighter requires maximum power, e.g. during take-off or in aerial combat. Termed “lighting the afterburner”, this is achieved by pumping fuel into the engine’s exhaust.]

The Kaveri’s dry thrust is deemed adequate for the USAV, which does not require wet thrust since its survival depends on stealth (invisibility to radar) rather than on speed or manoeuvrability. The Kaveri will propel the USAV with dry thrust alone, eliminating the afterburner.

“Since the USAV will weigh less than 10 tonnes, the Kaveri’s 50 KN will suffice. And, with the afterburner removed, we would significantly reduce the weight of the Kaveri,” says a top DRDO scientist.

GTRE has a three-fold plan for perfecting the Kaveri for the USAV. First, it will remove the design flaws that were detecting during testing in Russia in 2010-11; then, after ground testing in Bangalore, the Kaveri will undergo a round of confirmatory tests in Russia; finally, it will be fitted on a Tejas fighter for flight tests.

Meanwhile, the Bangalore-based Aeronautical Development Establishment (ADE), another DRDO laboratory, will develop the USAV. Four years from today, the Kaveri --- having proved itself on the Tejas --- will be mated with the USAV.

“After extensive ground testing at GTRE, the Kaveri will go back to Russia for flight-testing to ascertain that all the problems have been solved. This is essential for airworthiness certification. Finally, we will test the Kaveri in the single-engine Tejas fighter,” says Dr CP Ramnarayanan, Director, GTRE.

The Aeronautical Development Agency (ADA), which oversees the development of the Tejas, confirms that it will provide a Tejas prototype for flying with the Kaveri. It has even nominated an aircraft --- the first prototype, numbered PV-1 --- which is currently being used for flight-testing new systems.

“(The PV-1) was originally built to support the Kaveri engine. While the engine, in its present form, would not suffice for the Tejas, a Kaveri “dry engine” could be used for one of the futuristic unmanned systems,” says PS Subramanyam, Director, ADA.

GTRE has asked the MoD for Rs 595 crore to develop the Kaveri dry engine for the USAV. This will fund the building of two new Kaveri engines, costing some Rs 50 crore each; and flight testing in Russia, which cost Rs 80 crore in 2010-11 and could cost significantly more now.

“We will take 48 months from the date we get clearance from the government, for completing 50 hours of testing the Kaveri on the Tejas LCA. During the last 12 months, we will actually fly the Tejas with the Kaveri,” says Ramnarayanan.

The defence minister told parliament this month that the Kaveri project was sanctioned in March 1989 at an estimated cost of Rs.382.81 crore, and was to be completed by December 1996. This was revised [in 2005] to December 2009, while the cost was enhanced to Rs 2,839 crore. So far, Rs 1,996 crore has been actually spent on the Kaveri.

Defending the cost escalation, GTRE points out that comparable engines --- such as the General Electric F-404 and the Russian Klimov RD-33 --- cost the equivalent of Rs 8,000 crore to build in the 1990s, and would cost Rs 12,000-14,000 crore today.