A subsonic aircraft has unswept wing which has maximum lift coefficient of 1.4. Now, consider wing is provided sweep of 25° at quarter chord point. Now, determine the change in maximum lift coefficient due to the provision of sweep.

Correct Answer: Maximum Lift coefficient will be reduced by 0.2580 amount
Given, unswept maximum lift coefficient CL1 = 1.4 Now, sweep of 25° is provided at quarter chord point. Hence sweep angle at quarter chord s = 25° Maximum lift coefficient CL2 = CL1*0.9*cos (a) = 1.4*0.9*cos (25°) = 1.1419. Now, change in maximum lift coefficient = CL2 – CL1 = 1.1419 – 1.4 = -0.2580. Hence, by implementing the sweep of 25° maximum lift coefficient is reduced by 0.2508 unit.