In terms of wake turbulence, how much separation is required for large/heavy behind a B757?

The correct requirement for separation behind a B757 is 4 miles when considering wake turbulence. This distance is prescribed to ensure that aircraft following a B757 are adequately spaced to mitigate the risk of experiencing wake turbulence, which can be particularly hazardous for smaller or lighter aircraft.

Wake turbulence is created by the passage of an aircraft through the air and consists of two vortices that spin off the wingtips, trailing behind the aircraft. The strength of these vortices depends on the weight, speed, and configuration of the leading aircraft. The B757, categorized as a large/heavy aircraft, generates a significant wake turbulence that can affect following aircraft. Therefore, air traffic controllers must enforce appropriate separation distances to provide enough time and space for the vortices to dissipate before another aircraft passes through the same airspace.

For lighter aircraft, the 4-mile separation helps to ensure they avoid entering the wake turbulence zone created by the heavier aircraft like the B757, protecting them from potentially severe turbulence effects. The specific separation distance is established by aviation regulatory bodies based on extensive research and operational experience to enhance safety in air traffic operations.