What We Hear – Expectation Bias
A pilot calls the tower and reports ready for departure on Runway 10. The controller clears the pilot for takeoff on Runway 17. The pilot reads back his clearance for takeoff on Runway 10 – and then stops on the runway when he spots an aircraft inbound opposite direction for his runway.
The Air Traffic Control System is heavily dependent upon verbal communication to exchange information between controllers and pilots. Hearing what we expect to hear is frequently listed as a causal factor for pilot deviations that occur both on the ground and in the air. In the scenario above - the pilot expected to be cleared for takeoff on Runway 10 – and the controller expected to hear from an aircraft that had been taxied to Runway 17. These professionals were captured by their own expectations.
Eurocontrol defines ATC expectation bias as “Having a strong belief or mindset towards a particular outcome”. A recent analysis of runway incursion data shows that expectation bias is one of the most common causal factors for pilot deviations. Data from the Air Traffic Safety Action Progam confirms this fact.
What can you do as a pilot to mitigate expectation bias? Understand that expectation bias often affects the verbal transmission of information. When issued instructions by ATC – focus on listening and repeat to yourself exactly what is said in your head – and then apply that information actively. Does the clearance make sense? If something doesn’t make sense (incorrect call sign, runway assignment, altitude, etc.) – then query the controller about it.
Don’t let your expectations lead to a pilot deviation. Listen carefully – and fly safe!