To quote the text of that portion of the original RfP draft, the IAF put it down that supercruise was required for “game-changing tactical advantages in offensive and defensive spectrum” and also “lowered IR signature, rapid theater presence, evolutionary sensor/weapon kinematics and denial of enemy reaction time”. Interestingly, the IAF refrained from putting down any additional parameters for the supercruise regime it was looking for.
Obviously, the IAF has never operated supercruising aircraft before. Its Hunters routinely went briefly supersonic in steep dives, but never has it operated aircraft that could travel faster than sound in sustained level flight with a meaningful military payload without engine reheat. For all the criticism that the Indian armed forces usually cut and paste from brochures to draw up their qualitative requirements, the IAF did some homework in earnest on supercruise. As a matter of fact, during one meeting of the Aeronautical Development Agency (ADA) in 2007, at which the Tejas’ propulsion problems were being deliberated upon, then Chief of Air Staff FH Major apparently said that the agencies involved needed to ensure that the next-generation engine that would ultimately power the Medium Combat Aircraft (MCA) and the final integrated airframe, had supercruise capabilities.
Between 2004-07, the IAF had done some serious reading on supercruise, and formulated an opinion on the subject, apparently still a contentious one in military aviation research. However, the IAF finally decided not to push its case for supercruise in the final RfP document, which is why it does not exist in the final tender that was sent out to Saab, MiG, Boeing, Lockheed-Martin, EADS and Dassault. In the event, that was a wise decision. Because it would probably have sliced away most or all of the contenders any way.
In January this year, a Gripen demonstrator aircraft — of the type on offer to India — achieved supercruise. Pilot Magnus Ljungdahl said, “The flight was conducted over the Baltic Sea, my altitude was 28,000 feet and the speed achieved was above Mach 1.2. Without using afterburner I maintained the same speed until I ran out of test area and had to head back to the Saab Test Flight Centre in Linköping.“
Does one test flight prove that the Gripen IN can supercruise? Does that go onto the aircraft’s CV then? Possibly. The Eurofighter can also apparently supercruise according to EADS. But Saab and EADS don’t talk about what fuel/weapons loads the aircraft can carry when supercruising. The other four jets in the competition make no bones about not being able to supercruise, though there’s plenty of hypocritical rhetoric that still comes the IAF’s way from Boeing/Lockheed about how supercruise is not as economic, useful or tactically dramatic as it’s made out to be in a modern military scenario, and therefore shouldn’t seriously figure among the “x-factor” parameters that will be tested during the trial evaluations. A little rich, coming from the companies that tom-tom the F-22’s supercruise capability as though the aircraft has little else to offer.
I imagine the IAF has sunk its teeth meaningfully into the supercruise debate — because it is a debate. There are a huge number of considerations that go into the ability to supercruise, and it’s the total package that counts. An officer at the IAF’s top gun school TACDE rattled off a few of these considerations: fuel fraction, flow efficiency, air intake design that won’t shatter the turbofan compressor during the transonic flight spectrum, and dozens of other considerations.
These are, of course, entirely separate from operational envelope considerations, which would need to develop through doctrinal evolution, if and when the IAF does operate aircraft with a no-nonsense capability to supercruise in the real sense.
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