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Military Vs Civilian Turbofan Engines and Supercruise Technology

Updated on July 31, 2011

Difference between Military and Civilian Turbofan Engines: All current military aircraft use afterburning turbofan engines. The difference between military and civilian turbofan engines is that military jets use low bypass ratio turbofans and civilian jets uses high bypass ratio turbofan engines. High bypass turbofan engines are very efficient but they have large diameters and produce a lot of drag something least desirable in military aircraft. Turbojets though have high thrust but they are very inefficient, so military aircraft use a compromise between the two, i.e., low bypass turbofan engine.

What is Supercruise Technology? Afterburning vs Supercruise

Supercruise technology means to able to go supersonic without engaging afterburners. Of course, it requires a more powerful and an optimally tweaked bypass turbofan which is a fuel guzzler, but any time, it is more efficient than the afterburning system; assume both have same top speed; hence for a given fuel load, it will ensure longer loiter time and enhanced range.

Mid sky refueling by F22 Raptor - Supercruise enabled fighter jet
Mid sky refueling by F22 Raptor - Supercruise enabled fighter jet | Source

As far as supercruise implications to stealth are concerned they are very obvious, i.e., since the combustion gases pass through the turbine blades and then combine with the bypassed air, the exhaust as a result does not go to high temperatures as compared to burning hot afterburners (the combustion being more complete also ensures no smoke is produced; a problem that plagued the old Mig-29s. The engine MTBF (mean time between failures) is very high and maintenance and service life is also enhanced.

To quote from wikipedia source about supercruise, “Furthermore, without any need to carry large fuel loads, a supercruise technology aircraft can get a more favorable fuel fraction than afterburners”. Read more here: Wikipedia supercruise

When you compare performance of two aircrafts with similar top speeds one with afterburner and other without, you would find the fuel consumption of the one with afterburner at subsonic speed will be less as compared to the one with supercruise at same speeds. When at supersonic speeds, the former will be literally flushing out the whole fuel while the latter will show similar performance with much less fuel consumption and more importantly maintaining a lower IR signature.

Supercruise in no way can out accelerate a powerful afterburner. In fact supercruise was never meant to do so. It is a compromise between a decent mission critical speed and at the same time maintains a low observable profile.

Super Cruise More Effective than Afterburners

Least but not last, afterburning is a very crude yet effective way of boosting the speed of an aircraft but it is very inefficient and hence limits the range of an aircraft for a given fuel load. Moreover, using afterburners compromises all the IR sign suppression techniques (if you wish to incorporate stealth).The new generation aircraft are seeing supercruise as a de facto standard, especially when it is a well accepted fact today that once detected, the probability of escaping from a AAM/SAM is next to zero (hence there is more emphasis on stealth and LPI rather than speed.

The conclusion is that supercruise is much better without afterburners.


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