The old adage, ‘never assume anything in Air Traffic Control’ is as relevant today as it was 40 years ago.
Controllers do base operational decisions on an expectation that a pilot will comply with control instructions every day. It is reasonable for this to occur however what is important to ALWAYS remember, is that those reasonable expectations are still in fact ASSUMPTIONS.
It is imperative therefore, that an effective and continuous scan is employed, which becomes a great defence towards assurance that those reasonable expectations are being realised and that the plan based on those expectations is appropriate and achieve the desired intent.
Expectation bias however, is a very powerful human condition when an individual’s expectations about an outcome influence perceptions of one’s own or others’ behaviour. As a result, this bias can erode the skills and techniques ‘normally’ applied to assure safe and efficient air traffic services to the point where safety margins are infringed.
Airservices has identified that a significant number of occurrences are influenced by expectation bias. Awareness of the influence expectation bias can have on your ability to perform ATC, is an important step in mitigating the condition from developing.