Question: A thin two-dimensional flat-plate airfoil is fitted with a trailing-edge flap of chord 100e% of the airfoil chord. Show that the flap effectiveness,
![713_a1.png](https://secure.tutorsglobe.com/CMSImages/713_a1.png)
where α is the angle of incidence and η is the flap angle, is approximately 4 √e/π for flaps of small chord.