Definition
The minimum runway length required for a transport-category jet to land on a dry runway under FAR Part 25 rules, calculated by taking the actual demonstrated landing distance and dividing it by 0.6. The 0.6 divisor adds a 67% safety margin (the 'cushion') to the demonstrated stopping distance, ensuring the airplane can be dispatched only to runways that are significantly longer than what a test pilot needs to stop on a dry surface.
Plain English
The runway length the airplane must legally have available when planning a landing on a dry runway. It is the actual stopping distance plus a built-in safety margin, so the runway is always longer than what is strictly needed.
Context Anchor
Seen in jet landing performance planning, especially in charts that compare the airplane’s stopping distance with the runway length required by regulation.
Derivation
Cushion' here means a built-in safety margin — extra runway beyond the bare minimum, the way a cushion absorbs impact. It is not a technical term but a working pilot expression for the buffer the regulation builds in.
Why Pilots Care
Provides the operational margin that prevents runway overruns by ensuring the available runway exceeds the minimum stopping distance under dry conditions.
Grounding Statement
If a jet could stop in 3,000 feet after crossing the threshold, the required dry runway field length with cushion would be longer than 3,000 feet because the rule requires extra runway margin.
Intuition Check
“Cushion” does not mean a softer landing or extra comfort; it means extra runway length added as a safety margin. “Field length” does not mean the whole airport property; here it means the runway length required for the landing calculation.
Example Sentence 1
Dispatch checked the dry runway field length with cushion against the available runway at the destination before releasing the flight.
Example Sentence 2
At the destination airport the pilot compared the reported runway length against the required dry runway field length with cushion before committing to the approach.