Sweep creates a dihedral-like effect

Sweep creates a dihedral-like effect

Steve Seibel
www.aeroexperiments.org

This page was last modified on September 13, 2006

 

This diagram (see the rightmost diagram in the middle of the page) illustrates the yaw torque (weathervane effect) generated by a sideways airflow (sideslip) interacting with a swept wing.

The same diagram also shows that when we view the aircraft from above, the leading edge of the "upwind" or "leading" wing meets the relative wind more "squarely" than does the leading edge of the "downwind" or "trailing" wing. In other words, the "upwind" or "leading" wing has less sweep in relation to the relative wind than does the "downwind" or "trailing" wing. This means that the "upwind" or "leading" wing will experience a higher lift coefficient than the "downwind" or "trailing" wing. In other words, the "upwind" or "leading" wing will create more lift than the "downwind" or "trailing" wing. This will create a dihedral-like roll torque in the "downwind" direction--in this diagram, the right wing will tend to rise and the left wing will tend to drop.

(Source of diagram: "Aerodynamics for naval aviators (NAVWEPS 00-80T-80)" by Hugh H. Hurt (1965, Office of the Chief of Naval Operations, Aviation Training Division, for sale by the Supt. of Documents, US Govt. Printing Office))

See these sources for more on the dihedral-like effects of sweep:

"Swept Wings and Effective Dihedral" by Bill and Bunny Kuhlman. From RC Soaring Digest, January-March 2000.

 

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