Stopway and Clearway

Stopway Definition and Function

A stopway is a specifically prepared area beyond the take-off runway, aligned with the runway centreline, and at least as wide as the runway itself. Its surface is designed to support the full weight of the aircraft in case of a rejected take-off, allowing the aircraft to decelerate safely without sustaining structural damage. The stopway is included in the calculation of Accelerate-Stop Distance Available (ASDA), which is the maximum distance in which an aircraft can accelerate to a decision speed (V1) and then abort the take-off, coming to a complete stop.

Clearway Explained

A clearway is a defined, obstacle-free area beyond the runway, at least 152 metres (500 feet) wide, centred on the extended runway centreline. It is under airport authority control and is free from obstacles except for very low-profile items like threshold lights. The clearway allows an aircraft, after leaving the runway surface, to continue accelerating and become airborne if needed. The clearway is used in calculating the Take-Off Distance Available (TODA), which is the length over which the aircraft can accelerate and lift off.

Stopway vs Clearway

• Stopway is a load-bearing surface for stopping after an aborted take-off.
• Clearway is an obstacle-free area for continued acceleration and lift-off, but it is not designed for ground roll or stopping.
• The stopway increases ASDA, while the clearway increases TODA.
• The clearway length used in performance calculations must not exceed 50% of the Take-Off Run Available (TORA).

Effects on Take-Off Mass

Using a stopway allows for a higher field-length-limited take-off mass because it increases the ASDA, providing a longer distance to stop if the take-off is rejected. A clearway, by increasing the TODA, can also permit a higher take-off mass, as it allows the aircraft more distance to achieve lift-off, especially in cases where obstacle clearance is a limiting factor.

Operational Considerations

Pilots must ensure that declared distances (TORA, TODA, ASDA) are understood and correctly applied. The presence and dimensions of stopways and clearways directly influence take-off performance calculations and decision-making, particularly in marginal runway length situations.