A pilot’s job is as difficult as it is exciting. Not only are they responsible for helping the passengers reach the destination on time, but also for their safety. As commonsensical as it may sound, passenger safety is always the first priority for any pilot.
Aborting a takeoff is commonplace. Takeoffs may need to be aborted because of any reason, ranging from tailwind pattern changes to unexpected guests on the tarmac. However, there is one rule which helps pilots decide when to abort takeoffs – the 50-70 rule.
Simply stated, the 50-70 rule states:
If you have not reached 70% of your takeoff speed by the time you reach 50% of the length of the runway, abort your takeoff.
Takeoff speeds are calculated by pilots before departure depending upon the aircraft total weight, ambient temperature, altitude of the airport and the slat/flap setting. Also, the exact runway length is also known to the pilots. Therefore, the 50-70 rule is a very handy tool for pilots to avoid crisis situations.
Runways are required to have distance markings which help pilots take cognizance of the runway lengths on the go.
Thus, the pilots need to determine whether the aircraft has attained 70% of the takeoff velocity on or before the runway halfway point. If the aircraft has not been able to attain 70% of the takeoff velocity by the time it reaches the runway halfway point, the pilots need to abort the takeoff, as it is mathematically proven that the aircraft will not be able to successfully take off using the remaining runway.