“An emotion typically resulting from the violation of an expectation or the detection of novelty in the environment” (American Psychological Society, 2022).

Surprise represents the difference between expectations and reality. That can mean something happening that is not expected or something not happening that was expected.

Surprise and the startle reflex

Although rare, a sudden unexpected event may trigger an immediate and involuntary startle reflex directly affecting information processing capability and situational awareness, which can last for some time and have implications for the affected individual's decision making ability. In such a situation the affected individual may act irrationally.

Risk mitigation of surprise

In aviation surprise is not uncommon and can be mitigated through training, procedures, crew resource management (CRM) and experience.

  • Exposure to unexpected events in training will reduce the risk of a non-standard response. Pilots can be taught to respond to surprises rationally, focusing on safe flight (aviate, navigate, communicate), assessing what has happened or not happened and coming up with a plan.
  • Standard operating procedures (SOPs) provide guidance to deal with many unexpected situations, reducing cognitive load on the pilots.
  • CRM: Teaching pilots to distinguish the difference between a (rare) startle response from (more common) surprise can help an unaffected pilot recognise when a colleague has been affected and is unknowingly responding in a way that is leading to an unsafe condition requiring intervention. The importance of the Pilot Monitoring (PM) having the confidence to act without delay, if necessary, cannot be overstated.
  • Airmanship: With experience, pilots are less likely to be surprised. Greater situational awareness that comes from managed cognitive load, professional knowledge and experience means that certain events are not wholly unexpected. For example, encountering clear air turbulence in the vicinity of a jet stream or encountering birds on final approach to a coastal airport.

Further considerations

  • An unexpected happening mid-way through a checklist can cause distraction and either failure to complete the checklist or the checklist actions not being completed correctly. In such a circumstance it is advisable to start the checklist from the beginning.
  • Indirect effects: The unexpected event may have occurred on the flight deck of an aircraft ahead or in the ATC control room. Start "tidying up". create spare mental capacity to be ready to deal with any ramifications that will affect your flight.

Further reading



SKYbrary Partners:

Safety knowledge contributed by: