At what height above the runway does the wet runway balanced field length (BFL) end?

The wet runway balanced field length (BFL) ends at a height of 15 feet above the runway. This height is significant because it is during this phase that the aircraft transitions from ground effect to truly flying. At 15 feet, the aircraft has gained sufficient aerodynamic lift to safely clear obstacles while still adhering to the specific performance characteristics associated with a wet runway.

In aviation, BFL is a critical metric that helps in determining the necessary distance required for an airplane to take off or stop based on its weight, environmental conditions, and runway surface conditions. On a wet runway, the stopping or takeoff performance can be affected by reduced friction; thus, understanding the height at which BFL ends is essential for pilots to ensure safe operations.

The other heights listed—10 ft, 25 ft, and 30 ft—do not correspond with the established parameters for BFL on a wet runway, making the choice of 15 ft as the endpoint of wet runway balanced field length the correct response.