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As the lift dumpers are extended on landing they cause the air to move away from the wing. Also as the flaps are extended fully the airflow further separates from the wing? Does this cause the wing to stall even if its at 0 AoA during landing rollout?


2 Answers 2


Stall for a wing is defined as:

a reduction in the lift coefficient generated by a foil as angle of attack increases. This occurs when the critical angle of attack of the foil is exceeded. (Wikipedia, citing from: Crane, Dale, Dictionary of Aeronautical Terms)

So to be sure we should do testing to find the wing’s critical AoA in this state. If it's greater than 0 then the answer is no. It even can be generating some lift at this moment and given the sufficient thrust and speed it can probably take off (not advised).

But if we think of stall as turbulent airflow above the wing, the area behind the spoilers are definitely stalled but not the whole wing.

  • $\begingroup$ I don't think you can "think of stall as turbulent airflow above the wing". For sure, that happens at the stall point, but stall is precisely defined as the AoA when lift starts decreasing. The turbulence behind the spoilers indicates they might be "stalled", but I'd question whether there is even a concept of "stalled spoilers": do spoilers ever experience an increase in lift based on Aoa, such that it could decrease to even find the stall? $\endgroup$ Commented Jul 25, 2022 at 23:42

One way to look at it is, a stall requiring the exceedance of critical angle of attack, and the critical angle of attack not being exceeded in the landing, what has actually happened is the spoilers have transformed the wing from a wing into something else.

You could say that the lift dumpers transform the lift making airfoil into just a randomly shaped object, like a sofa or a row of deck chairs, that can't make lift, stalled or not..

  • $\begingroup$ One might even say that those “lift dumpers” deflect air upward adding downforce to the wing which increases the braking normal force. $\endgroup$
    – Jim
    Commented Jul 24, 2022 at 18:00
  • 6
    $\begingroup$ Technically, the fully deployed spoilers disrupt the airflow enough so that only minimal lift is generated by the wings. They actually create so much disruption, that regardless of AoA there will not be a coherent lift force generated at that speed. Effectively, that could indeed be described as an aerodynamic stall, at least by definition. The difference is in common sense. In this case, it is not a negative effect but actually desired to do so. It negates the wing lift so that the full weight of the plane rests on the gear for maximum breaking effect. $\endgroup$
    – Adwaenyth
    Commented Jul 25, 2022 at 12:22

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