Welcome Guest. Sign in or Signup

2 Answers

Do flaps or leading edge devices change an airfoil’s critical angle of attack?

Asked by: 9534 views Aerodynamics

Do flaps or leading edge devices change the angle of attack at which the airfoil will stall?  My research online seems to favor a decrease in critical AOA when flaps are extended, and an increase in critical AOA when leading edge devices are extended.  I just can't quite grasp why that is.  Can someone verify whether or not that is correct, and if so, why? 

Ace Any FAA Written Test!
Actual FAA Questions / Free Lifetime Updates
The best explanations in the business
Fast, efficient study.
Pass Your Checkride With Confidence!
FAA Practical Test prep that reflects actual checkrides.
Any checkride: Airplane, Helicopter, Glider, etc.
Written and maintained by actual pilot examiners and master CFIs.
The World's Most Trusted eLogbook
Be Organized, Current, Professional, and Safe.
Highly customizable - for student pilots through pros.
Free Transition Service for users of other eLogs.
Our sincere thanks to pilots such as yourself who support AskACFI while helping themselves by using the awesome PC, Mac, iPhone/iPad, and Android aviation apps of our sponsors.

2 Answers



  1. Vidura Asanka Jayawardene on Jun 07, 2014

    From what I know that is correct. The angle of attack is the angle between the cord line and relative airflow, extending the flaps will change the cord line in such a way that the normal angle of attack of the wing relative to the airflow is increased, so now the change in angle required to reach the critical AOA is less hence the critical AOA is deceased. The whole opposite occurs when leading edge devices are deployed. I wish I could draw this out then I can show you whats happening….

    0 Votes Thumb up 3 Votes Thumb down 3 Votes



  2. Brian on Jun 11, 2014

    It depends on the type of flap. The definition of chord line is a line drawn from the leading to the trailing edge of a clean airfoil. Since flaps increase this angle (called the virtual chord line) and slats decrease this angle the critical AOA is decrease when flaps are introduces. Conversely, slats decrease the angle of the chord line (again referred to as the virtual chord line) so the actual stalling AOA is greater than in an clean configuration. I will try to get some pictures posted tomorrow.

    +3 Votes Thumb up 3 Votes Thumb down 0 Votes


The following terms have been auto-detected the question above and any answers or discussion provided. Click on a term to see its definition from the Dauntless Aviation JargonBuster Glossary.

Answer Question

Our sincere thanks to all who contribute constructively to this forum in answering flight training questions. If you are a flight instructor or represent a flight school / FBO offering flight instruction, you are welcome to include links to your site and related contact information as it pertains to offering local flight instruction in a specific geographic area. Additionally, direct links to FAA and related official government sources of information are welcome. However we thank you for your understanding that links to other sites or text that may be construed as explicit or implicit advertising of other business, sites, or goods/services are not permitted even if such links nominally are relevant to the question asked.