# What is the main role of the Angle of Attack of an airplane, as in mainstream explanation of lift? [duplicate]

The question is conceptual and simple, it needs no more information to answer it. And I wish not to influence the answerer.

## 1 Answer

For simplicity, we start with a symmetrical airfoil.

The angle of attack modulates the amount of lift the wing will generate at a given airspeed & air density. At zero AoA, zero lift is generated. The amount of lift increases with increasing AoA up to the point of flow separation, where the amount of lift stops climbing and falls off (but not to zero).

If we look at the momentum explanation for lift, increasing the AoA tips the momentum vectors of air parcels further downward, increasing the magnitude of the reaction force on the wing- which constitutes lift.

If we look at the pressure distribution explanation, greater AoA increases the pressure difference between the top surface of the wing and the bottom surface, which means more lift.

As explained elsewhere, the true cause of lift must take both of these simplified mechanisms into account along with such things as the flow field several chord lengths away from the wing before a full explanation will emerge.

• "increasing the AoA tips the momentum vectors of air parcels further downward" Are you trying to say that air parcels are pushed downward? Isn't that forbidden to say? 😉 Commented Sep 16, 2022 at 5:28
• @ArpiSz you could pull the incoming fluid upward without pushing the outcoming flow downwards instead. But I understand that you would not accept this, while you go around the forum, opening new questions and looking for someone who gives you the answer you want.to hear Commented Sep 16, 2022 at 6:55
• @ArpiSz, what do you mean, "forbidden to say"? Commented Sep 16, 2022 at 17:16
• @Niels Nielson I intended the phrase "forbidden to say" as a joke referring to the fact that no-one seems to accept that Lift comes from the wing pushing down air. That was what your comment suggested by mentioning downwards momentum of air parcels. I am only getting rejection and even my question above was downvoted. How can one downvote a question which is not a troll ? They downvote a question because they don't like it, and they don't have to explain. Commented Sep 18, 2022 at 20:54