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Where did the false "equal transit-time" explanation of lift originate from?

It's supposedly a "widely circulated" false claim that wings generate lift because of their asymmetric shape, forcing air above to travel faster so that they meet up on the trailing edge at the sam...

Its origin now seems to be lost in the mists of time although it may be that its use in aircrew training manuals gained for it a popularity which extended to school textbooks and even the occasional British A Level examination paper. I could not find any physical justifications for it, perhaps its surface level intuitiveness stems from being conflated with some kind of continuity equation/condition, almost as if air parcels split at the leading edge, must rejoin at the trailing edge otherwise there would be a "build up of air" on the side with the longer path (the "equal transit-time" requirement is of course not necessary to avoid this). This Quora question seems to suggest there is some confusion related to this: Why continuity equation must be followed by aerofoil?

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