Reconsider the lift-drag data for the NACA 4412 airfoil from Prob. 8.83.
(a) Again draw the polar lift-drag plot and compare qualitatively with Fig. 7.26.
(b) Find the maximum value of the lift-to-drag ratio.
(c) Demonstrate a straight-line construction on the polar plot which will immediately yield the maximum L/D in (b).
(d) If an aircraft could use this two-dimensional wing in actual flight (no induced drag) and had a perfect pilot, estimate how far (in miles) this aircraft could glide to a sea-level runway if it lost power at 25,000 ft altitude.

Transcribed Image Text:

A lie tangent to the polar plot 1.5 CL sthe slope o max 0.5 0.000 0,004 0.008 0.012 0.016 0.020 CD