At the Farnborough Airshow, I saw an F-35 take off with air brake behind the cockpit extended. Why would they do that?
3 Answers
That is not the air brake, but the cover for the vertical air intake on the F-35B model, which is operated by the RAF.
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7$\begingroup$ To be clear, what OP saw is the cover in the open position, to enable the vertical take off. $\endgroup$– TimCommented Jul 31, 2022 at 21:46
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$\begingroup$ I've added an image, but note that the shape and position of the cover on the actual plane is different from the one shown. $\endgroup$– SQBCommented Aug 1, 2022 at 8:59
The airbrake is not a single piece on the F35, like the F15 have. That is just a fan cover for the F35 hovering variant. For airbrake, the F35 use the rudders, flaps and ailerons all at the same time.
Not an expert on F-35 or whether it would make aerodynamic or even structural sense, but to add to what others have said, a typical air break is designed to hinder horizontal movement by means of increased drag.
If your goal is a steep vertical take-off, such as some F35 models are capable of doing, then applying an air break could possibly be harmless or perhaps even beneficial by reducing the horizontal movement during the procedure (at least when the winds are calm).
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1$\begingroup$ An air brake will slow an aircraft relative to the airspeed, and not the ground speed. Additionally, the deceleration caused by an air brake is weakens as the velocity differential drops. Due to these two factors, the effect you are talking about is not very useful. $\endgroup$– AronCommented Aug 4, 2022 at 7:37