Saturday, February 23, 2013

Video: the advantages of an afterburner

I'm sure many readers know that most military fighter and strike aircraft are equipped with afterburners.  Wikipedia describes them thus:

An afterburner (or a reheat) is an additional component present on some jet engines, mostly military supersonic aircraft. Its purpose is to provide an increase in thrust, usually for supersonic flight, takeoff and for combat situations. Afterburning is achieved by injecting additional fuel into the jet pipe downstream of (i.e. after) the turbine. The advantage of afterburning is significantly increased thrust; the disadvantage is its very high fuel consumption and inefficiency, though this is often regarded as acceptable for the short periods during which it is usually used.

Pilots can activate and deactivate afterburners in-flight and jet engines are referred to as operating wet when afterburning is being used and dry when not. An engine producing maximum thrust wet is at maximum power, while an engine producing maximum thrust dry is at military power.

There's more information at the link.  To illustrate, here's a US Navy F/A-18 Hornet taking off from an aircraft-carrier with both its engines in full afterburner.  The orange flames in the exhaust nozzles are unmistakeable.  (Image courtesy of Wikipedia.)

To illustrate the increased power of an engine in afterburner, here's a video clip from the Royal Norwegian Air Force, showing six of its F-16 Fighting Falcon aircraft taking off from a very cold and wintry Ørland Main Air Station.  The first two aircraft use afterburner, and lift off from the ground shortly after passing the photographer.  The third and fourth are using military power (i.e. without afterburner) rather than maximum power (i.e. with afterburner), and take much longer to accelerate to takeoff speed, traveling much further down the runway before they can get airborne.  The final two aircraft again use afterburner, and take off in a shorter distance.  It's a graphic illustration of how much power is added by going to afterburner, albeit at the penalty of much higher fuel consumption.  I recommend watching the clip in full-screen mode.



BobF said...

I've worked on many different types of aircraft over the years, but nothing was quite like an F-4 hitting afterburner - had its own special characer. But then again, for sheer sustained and raw power, a line of B-52s doing Minimum Interval Takeoff with all that water injection (F models) would rattle the bones, not to mention drive tree huggers absolutely nuts. Geez, I miss those days.

Old NFO said...

Yep, nothing like burner to watch the gas gauge drop like a ROCK!!! :-)

Will said...

I wonder how much more tire life you get by using this? Less total time on the roll, and much shorter time at higher speeds, which is hard on tires.

No help on landing, of course. Well, except there may be less fuel on board! That's less weight, so better for the tires...

Anonymous said...

I always thought of the J79's burners as devices for converting JP-5 to noise and smoke.