The ability to get high maneuverability in a tactical aircraft has always taken some degree of compromise. Ideally a designer would seek stability, but to gain the necessary agility to change directions quickly you introduce sacrifices. What you gain in one place you give up in another.
A solution in the last couple of generations of aircraft has been bringing computers into the control system. The electronics can cut the reaction loop effectively and make continual recoveries to regain control before disaster. All well and good when everything is working.
Wings function on angle-of-attack. At some point called the critical AOA, the wing protests and stops doing good stuff and starts doing bad things. At the simple level that means no more increases in lift, but lots of increase in drag. That's an aerodynamic stall. More exotic wings get more exotic occurrences at the extremes of AOA. That is called "departure from controlled flight" and may or may not be recoverable.
Engines have their own AOA problems. A jet needs a diet of nice smooth, sub-sonic air. When AOA increases to extreme levels, the engine can protest with the jet equivalent of a back-fire. That's a compressor stall. It may be so violent as to destroy the engine or it could be so subtle as to remind you of spark knock in the family car.
The really good jets will integrate incredible aerodynamics with engines that are extremely flexible in their demands for airflow and control it all with a magical fly-by-wire stability system to help the pilot control it all. Those jets can fly very slowly at very high AOA. This is usually demonstrated at air shows.
Sometimes this happens:
The event was practice for an airshow flyby at high AOA and low altitude. Some eye witness accounts report "sparks and flame" from the engine accompanied by strange noises. No sparks visible on the video, however.
Possibilities include flight control malfunction, aerodynamic device failure such as leading or trailing edge flaps, engine flame out with yaw, some combination of factors.
1 comment:
Oh well, looks like the guy got out ok. Hope that was actually the case. It amazes me in situations like that how good the reaction time is for these guys. To go from everything's great, to "what was that?", to committing to an ejection, in mere seconds, goes well beyond the cognitive processes of the rest of us herd animals. The fact that it turns out for the best so often speaks volumes about the training these gus have.
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