What is the impact of a stopway/clearway on the allowed take-off mass and appropriate V1 when using an unbalanced field?

In the context of using an unbalanced field, the presence of a stopway can significantly affect the performance calculations related to take-off. A stopway is an area beyond the runway that is not suitable for takeoff but can be used to decelerate the aircraft in the event of an aborted takeoff. When a stopway is available, it allows for higher take-off mass because the aircraft can safely use the stopway to stop in case of an emergency. This effectively means that the aircraft's take-off distance required can be reduced, as there is additional space available if needed.

As for V1, which is the decision speed during takeoff, when a stopway is present and allows a higher take-off mass, it can also result in the need to adjust V1 upwards. This is due to the increased energy required for a heavier aircraft to reach the required speed for takeoff. Essentially, with the increased take-off mass and the potential for a longer take-off roll, V1 is positioned higher to ensure safe abort decisions can still be made without compromising safety standards.

In summary, the presence of a stopway enhances the take-off performance envelope by permitting a higher take-off mass and can influence V1 positively, allowing it to be adjusted