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3 Answers

Dihedral + Lateral Stability

Asked by: 1602 views Aerodynamics

Hi AskACFI, I am finding it extremely difficult to visualize how dihedral designs improve lateral stability. I understand: 1. Dihedral angle is the angle that each wing makes with the horizontal. 2. If a disturbance causes one wing to drop, the unbalanced force produces a sideslip in the direction of the downgoing wing. I am confused: How does the flow of air strike the lower wing at a greater angle of attack than in strikes the upper wing?  

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3 Answers

  1. Dan S. on Jun 27, 2015

    Take a look at pages 300-303 in Aerodynamics for Naval Aviators, for a good explanation and diagram. It has to do with a temporary change in lift vector for the up going wing vs the down going wing. Just do a google search and you can read the applicable pages.

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  2. KiwiInstructor on Jul 02, 2015

    stability is a pain to teach yet alone explain without pictures, if your really interested find yourself an instructor and a whiteboard 😉

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  3. Thomas Hoshino on Sep 11, 2015

    When the airplane banks without turning, it enters a sideslip condition. What this means is that the relative wind takes on a parallel and opposite component to this motion. visualize looking down the longitudinal axis of the banked aircraft. Ignoring the forward velocity, imagine a vector showing the aircraft\’s slipping motion in the direction of bank extending from the axis. The new component of relative wind is equal and opposite this sideslip vector. Note the angle the relative wind makes with each wing and it will be apparent that the lowered wing experiences a higher angle of attack and the raised wing has either a neutral or negative AoA depending on the exact direction of the relative wind.

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