For determining the basic runway length, the landing case requires that aircraft should come to a stop within p % of the landing distance. The value of p is A. 40 % B. 50 % C. 60 % D. 75 %

The correct answer is C. 60 %.

The basic runway length is the length of runway required to bring an aircraft to a safe stop under normal landing conditions. The landing case requires that the aircraft should come to a stop within 60% of the landing distance. This is to allow for a margin of safety in case of unexpected events, such as a gust of wind or a brake failure.

Option A is incorrect because it is too low. A margin of safety is required to allow for unexpected events.

Option B is incorrect because it is too high. A runway that is too long is expensive to build and maintain.

Option D is incorrect because it is not a valid percentage.