# What happens to the high pressure below an airfoil when the angle of attack increases?

I recently came across this question in a principles of flight exam:

When the angle of attack of an airfoil increases

1. the high pressure below the airfoil increases, the induced drag increases
2. the high pressure below the airfoil decreases
3. the induced drag decreases
4. can't remember this option

I chose 1. as the correct answer and it looks like I got it wrong. Although, I cannot tell for sure.

I know the induced drag will increase, but will the high pressure underneath the airfoil increase or decrease with an increase in angle of attack?

• What makes you think you were wrong? Nov 26, 2019 at 14:25
• What is held constant? Airspeed, or lift force? Some the answers below make an assumption that airspeed is held constant and lift force is not, which may not be justified. But I suspect the answer would be (a) in either case. Nov 26, 2019 at 19:37
• We need to find out what 4. was, 1. seems correct. 2. and 3. are incorrect. Nov 27, 2019 at 9:26
• @RobinBennett when I got my report back, that question number was marked incorrect. The description on the report was "lift and airfoils" and it was one of only 2 Principles of Flight questions. Nov 27, 2019 at 16:00
• @quiet flyer - good point, if you wanted to continue in level flight with an increased AOA, you'd have to reduce speed. The pressure would stay the same, and I'm not sure what the induced drag would do... It seems like a big assumption to me though. Nov 27, 2019 at 16:26