What is the recommended grade for a runway cross section to ensure water runoff?

A runway cross section is designed with a specific grade to facilitate proper drainage and prevent water accumulation, which can be hazardous for aircraft during takeoff and landing. The recommended range of 1% to 1.5% is generally accepted, as it successfully allows for effective water runoff without compromising the structural integrity or safety of the runway.

This grade ensures that water can flow off the surface efficiently, reducing the risk of hydroplaning and surface erosion. The chosen range strikes a balance by providing enough slope for drainage while maintaining a smooth surface for aircraft operations.

Grades that are lower than this may not effectively direct water away, leading to potential pooling, whereas grades that are too steep could impose challenges such as increased surface wear or uncomfortable landing conditions for pilots. Thus, the specified range is optimal for achieving effective water runoff in runway design.