Sunday, June 28, 2009

How important is Supercruise in the MMRCA competition?

Supercruise is not a qualitative requirement in the Indian Air Force's Medium Multirole Combat Aircraft (MMRCA) competition, but that doesn't mean it won't play a role. It should be noted that while the Request for Proposal (RfP) document was being drawn up (it took nearly three years), supercruise was listed in the original draft as a mandatory requirement that the IAF was looking for. Dockets of research on the physics of supercruise, including numerous unclassified presentations on the F-22 and Eurojet GmbH did their rounds around Vayu Bhawan for a while in 2004-05. An example of just what a catchword supercruise was for the MMRCA, is documented here.

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.

Photo ©Copyright Eurofighter

10 comments :

Abhiman said...

Hello Mr Aroor. The IAF's requirement for supercruise comes not due to any "foresight" or strategic thought, but merely by copying the trends at more advanced nations. Mr. Major was not at all known for knowledge of specifications. In an interview, he "blurted" that Tejas' engine has 75 kN reheat thrust and it needs to be 82 kN to be acceptable, when in fact the current GE-404 IN-20 engines have 82 kN reheat thrust. The IAF has demanded 90-100 kN reheat thrust.

I agree with the view that for the most part, our armed forces merely copy the trends of advanced nations that are on display in public air-shows and trade exhibitions.

Thank you.

Anonymous said...

a serious, well informed and informative article. excellent and a pleasure to read. i would like to add that i agree with the americans that supercruise is not a game-changing capability. an aircraft that supercruises still consumes far more fuel than an aircraft travelling the same distance subsonic. the economy is only marginal compared to flight using reheat.

Anonymous said...

"The other four jets in the competition make no bones about not being able to supercruise"
The main question is what supercruise speed, with what payload?
LM confirms supercruise at Mach 1.1 for F16IN loaded only with wingtip missiles. But they also say that they don't take that only take supercruise capabilities to account, with mach 1.5 and combat payload. If that is the reqirement, EF and Gripen NG might also not offer this capability, cause they are reported only with mach 1,2 and like u said nobody knows with what payload.
There are also reports of Rafale, and new Su 35 that confirms supercruise, but as long there is no equal definition it's not worth mentioning it.

Anonymous said...

Supercruise is (or should be) completely irrelevant. All these aircrafts have external weapon storage, and thus high drag. Burning fuel like mad while carrying two/four A2A missiles for 100 nm makes no sense.

Cruise at Mach 0.86, let the radars and AEW platforms 'catch' the targets, shoot at leisure from BVR. Whether defending a point-target, or going after a known hostile bird already in air, there's never a need for IAF to supercruise.

It is a bit like what they say about running away from police: you might outrun a police car, but you can't outrun the police radio. Supercruise is over-rated. It has more relevance to future supersonic bizjets than fighter aircrafts.

Anonymous said...

no other engine than f119 or al 41 engines provide supercruise capability to cross 1.5 mach without afterburner this too when stores are carried in internal bays.

anthony said...

Supercruise capability is either limited in these Gen 4.5 fighters (with minimal external payload) or they're just mere advertising gimmicks to the IAF brass.

What do you think?

Anonymous said...

Interesting. Who inspired this piece? The people afraid of supercruise? Name two next gen aircraft that will not be super cruise? By the way, none of the aircraft have really consistently demonstrated super cruise. So what's the big deal?

Anonymous said...

you are right antony,4.5 gen aircraft don't really supercruise with their external stores its just marketing stuff

Anonymous said...

You can find official EUROFIGHTER GMBH declassified documentation about loads and ranges while the fighter is flying in SC conditions.
More specifically, the 2006 Eurofighter Presentation to the Norwegian Air Force by Chris Worning (http://www.mediafire.com/?1mjwxy2jby1).
In page 53, Supercruise with 8 AAM´s for 250NM plus a 30 min CAP.


Cheers
Sintra

Picard578 said...

Rafale can supercruise at Mach 1,4 with 6 missiles.