When can a safe takeoff be made according to the runway available and critical field length?

A safe takeoff can be made when the runway available is equal to or greater than the critical field length. Critical field length is defined as the minimum runway length required for an aircraft to accelerate in the event of an engine failure, and to reach a safe takeoff speed while ensuring that the aircraft can either continue the takeoff or stop safely.

When the runway available meets or exceeds this critical field length, it indicates that the aircraft has sufficient distance to safely handle an engine failure occurring during the takeoff roll. Therefore, having a runway that is equal to or greater than the critical field length ensures that the aircraft can perform the necessary maneuvers to either take off successfully or stop if needed without endangering the crew or aircraft.

Runways shorter than the critical field length do not provide the necessary safety margin required for a complete takeoff profile under engine failure conditions, leading to potential accidents. Similarly, considering engine failure speed would not account for overall safety and operational parameters required for takeoff. Thus, for safe takeoff operations, the relationship between runway available and critical field length is crucial.