Unified Engineering Spring Term 2005

Problem P4. (Propulsion) L.O.’s C & D

In this problem you are to use the experimental 12 mph drag polar

C_D(C_L) that you measured for the Dragonfly wing in Lab 2.

Your Lab 2 data represents the drag of the wing alone: C_{D_lab2} = c_d + C_Di

To get the overall aircraft drag, you must add the constant drag

coefficient ~ 0.013 of the Dragonfly fuselage, as formulated

in the Lab 1 notes:

C_D = CDA_o/S + c_d + C_Di

C_D = 0.013 + C_{D_lab2}

This is the C_D(C_L) relation that you will use for the following questions.

The wing loading of the stock Dragonfly is approximately W/S = 15 Pa .

a) Assuming the overall propulsive efficiency is independent of speed,

use your C_D(C_L) data to graphically determine the C_L and corresponding

speed V that you would fly the Dragonfly to maximize range.

b) Same as a), but find the C_L and V for maximum endurance.

c) Repeat a) and b) for the case of the Dragonfly flying in a circle

at a constant 20 degree bank angle.