Lots of people often ask us questions that why does Tejas have red afterburner flame, and the Su-30MKI has blue?
Recently an aviation website also raised the same question in their lastest article titled “Why does Tejas have red afterburner flame, and the Su-30MKI has blue?”
The answer to the question is that the afterburner flame color has nothing to do with the type of fighter jet or type of engine of a fighter jet.
What is Afterburner?
An afterburner is an additional combustion component used on some jet engines, mostly those on military supersonic aircraft. Its purpose is to increase thrust, usually for supersonic flight, takeoff, and combat.
Afterburning injects additional fuel into a combustor in the jet pipe behind (i.e., “after”) the turbine, “reheating” the exhaust gas. Afterburning significantly increases thrust as an alternative to using a bigger engine with its attendant weight penalty but at the cost of very high fuel consumption (decreased fuel efficiency) which limits its use to short periods. This aircraft application of reheat contrasts with the meaning and implementation of reheat applicable to gas turbines driving electrical generators and which reduces fuel consumption.
Now, in this case, we have to understand both aircraft use a different engine, Sukhoi Su-30MKI use Russian engine Lyulka-Saturn AL-31FP where Tejas use American engine General Electric F404-GE-IN20
Sukhoi Su-30MKI Engine
The Su-30MKI is powered by two Lyulka-Saturn AL-31FP turbofans, each rated at 12,500 kgf (27,550 lbf) of full after-burning thrust, which enable speeds of up to Mach 2 in horizontal flight and a rate of climb of 230 m/s. The mean time between overhaul is reportedly 1,000 hours with a full-life span of 3,000 hours; the titanium nozzle has a mean time between overhaul of 500 hours.
HAL Tejas Engine
Where Tejas use The General Electric F404 aare a family of afterburning turbofan engines in the 10,500–19,000 lbf (47–85 kN) class (static thrust). The series are produced by GE Aviation. Partners include Volvo Aero, which builds the RM12 variant. The F404 was developed into the larger F414 turbofan, as well as the experimental GE36 civil propfan.
WTF?!?
Because they have different engines?!?
Hey why are seagulls grey but crows are black???
Because they are different. It’s a different bird so it’s a different color…
This isn’t hard to explain.
Different color means the fuel is burning at a different temperature. Blue color is higher temperature around 10000 Kelvin
Yellow color is cooler, closer to 2000 Kelvin
The afterburners for these engines are tuned to burn at different temperatures.
Why does that matter? Higher temperature means higher thrust.
Why not tune them all to burn at max temperature?
Because the materials used for the afterburning chamber could be different as well as different designs are more efficient at different temperatures.
Finally afterburners are not an on/off they also occupy part of the thrust controller and can be adjusted. The color/temperature can vary as the afterburners go from 0-100%…
That is how you answer that…. Feel free to add details and references.
Nicely explained..concise and to the point which a lay man can understand. Such questions will not be asked by engineer and scientist