# Re: Arms inot wings

```An upside down airfoil can lift in either direction at the will of the
pilot.  For example, a clipped-wing Cub (a Piper J-3 with wings shortened
and wing ribs moved closer together for increased structural strength)
will fly quite handily either right side up or upside down, lifting the
full weight of the aircraft, pilot, and fuel, albeit that it flys at quite
a nose-high attitude when upside down.  When upside down, you just
increase the angle of attack (AOA) by an increment of twice the angle of
attack for zero lift.  Under this circumstance (if you choose to visualize
lift by Bernoulli's equation - which I usually don't), the force generated
by the Bernoulli effect is still upward even though the plane (and wing)
are inverted.  Flip the plane back upright -- the Bernoulli effect
continues to lift upward, and the wing is now upright. To make an
asymmetric wing lift downward, you have to set the AOA equal to or less
than the AOA of zero lift when upright, and equal to or less than twice
the AOA of zero lift when inverted. The Bernoulli effect is affected by
the location of the stagnation point, the tangent to the camberline at the
trailing edge, and the shape of the flow field.  Bernoulli doesn't give
two hoots which side of the wing is facing up.
JimC

Patrick Norton wrote:

> Ralph Miller said
>
> <(On the other hand, an upside down airfoil wouldn't work at all)!>
>
> It works exactly the same, except the force generated by the Bernoulli
> effect is downward rather than upward.
>
> PTNorton@msn.com
> www.geocities.com/capecanaveral/galaxy/1962/

```