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Newbie Joined: Feb 02, 2008 Posts: 7 Status: Offline

I am new to this site and have a question about "super cruise"...the ability to go "fast" without after burner. I see the new F16 IN for India will have this capability and I was wondering if the plane can take off without afterburner also. What changes to the engines were made to get this capability? More compressor stages? Larger diameter compressors? Turbo fan or no turbo fan? Any help would be appreciated !

Ed

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Enthusiast Joined: Nov 21, 2005 Posts: 77 Status: Offline

"Supercruise" means having the ability to fly at mach 1 or faster without having to use afterburners. All f-16's can take off without afterburner, it has an excellent thrust to weight ratio. However, depending on the mission configuration (i.e. missiles, bombs, fuel tanks) afterburner might be required for takeoff. Newer engines are able to run at higher temperatures thanks to new technologies in engine design and materials, hence they are able to provide more thrust than older types. Also, these engines are turbofans but run at a near turbojet cycle due to their low bypass ratio.

Enthusiast Joined: Nov 21, 2005 Posts: 77 Status: Offline

"Supercruise" means having the ability to fly at mach 1 or faster without having to use afterburners. All f-16's can take off without afterburner, it has an excellent thrust to weight ratio. However, depending on the mission configuration (i.e. missiles, bombs, fuel tanks) afterburner might be required for takeoff. Newer engines are able to run at higher temperatures thanks to new technologies in engine design and materials, hence they are able to provide more thrust than older types. Also, these engines are turbofans but run at a near turbojet cycle due to their low bypass ratio.

Enthusiast Joined: Oct 19, 2006 Posts: 88 Status: Offline

I would caution that there is a very real difference between aircraft that can just barely reach supersonic conditions in a non-afterburning, clean configuration, and aircraft that are designed to carry a meaningful payload and fly at these conditions routinely.

A variety of historical aicraft could "supercruise" - just barely. But not with a payload that meant anything. The only airplane built to supercruise at conditions greater than Mach 1.5 with a full air-to-air compliment is the F-22. Everything else is just media hype.

The accepted definition of supercruise is "cruise at supersonic speeds without the use of afterburners."

The USAF says "to cruise at supersonic airspeeds (greater than 1.5 Mach) without using afterburner -- a characteristic known as supercruise."

Why would Congress buy Raptors that "supercruise" when most all modern fighters can all "supercruise" according to the original definition.

I agree with what has bee said above, MOST aircraft can't supercruise with weapons or external tanks, nor does supersonic combat occur. Lets not forget the F-16 and F/A-18 were designed around the MACH .8 combat concept. As found in previous conflicts, dogfights/combat rarely occur above that speed.

What supercruise will allow the Raptor to do, is get from point A to point B in a shorter amount of time with a lower fuel burn. (To a point) It is designed more like an interceptor of previous generations. (Get there fast, kill at range, get back home quickly...)

Quote:

(Get there fast, kill at range, get back home quickly...)

It may not be obvious to everyone, so I want to mention that "supercruise" at 1.5 mach requires much much more fuel than cruise at .8 mach. Supercruise is better than having to use burner, but unless you absolutely positively must fly at 1.5 to accomplish your mission, you'll have much greater range cruising at .8 mach. Not using burner, fuel flow at 1.5 will be around 4 or 5 times that at .8 for the same altitude. Climbing to a higher altitude would reduce that of course.

Newbie Joined: Feb 02, 2008 Posts: 7 Status: Offline

Thanks for all the answers...........Ed

johnwill, like you said at the same altitude, but the F-22 Supercurises at 60,000 ft, and .8 Mach cruise occurs at 20-36,000 feet. Also there is something I tend to get confused about as I always see different info, some sources I see shows that wave drag coefficient increases untill about 1.2-1.3 mach and maintains its coefficient above that speed. Other things I have seen have it increasing untill 1.2 and then decreasing to about half of its 1.2 value at 1.4-1.5. So if there is a drastic decrease in wave drag coefficient that would imply that actually drag does not increase AS RAPIDLY as it would with CONSTANT wave drag coefficents and as such range at Mach 1.6 could well be greater than range at 1.2. As the engineers here know range is dependant on, all other things constant, drag and SPEED, so if you have 10% increase is drag with a 20% increase in speed due to DECREASING drag COEFFICIENTS, that M1.6 Raptor flight profile could be more efficient than we think? Input? Ideas? Evidence for or against the change in coefficients? Love stirring up an issue in the name of knowlege.

Good points, all. I suspect every airplane has a different plot of Cd vs. mach, and some would obviously be better than others. I'm no expert in these areas, but I really doubt the Cd would drop enough between 1.2 and 1.6 mach to counteract the increase in dynamic pressure of 77%. The real Cd plots I've seen are similar to your first example, more or less constant above 1.2 mach.

Now I have a question. The USAF at one time required a pressure suit for operations above 50,000 ft. Does that still apply to F-22 operations at 60,000 ft.?

Like this one? Seen here in the F-15 Streak Eagle...

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