New research provides more evidence that unexpected events harm flight performance. The study used heart rate monitors and eye-tracking devices to investigate the psycho-physiological impact of being surprised in the cockpit.

The findings have been published in a master’s thesis and in Human Factors: The Journal of the Human Factors and Ergonomics Society.

The researchers were interested in examining the topic because of “several high profile accidents where what should have been routine responses were delayed or absent,” explained study author David O’Hare. “Most notably Air France 447 — where the crew’s actions seemed particularly hard to understand.”

O’Hare is a private pilot and professor of psychology at the University of Otago in New Zealand. His co-author and former student, Lana Kinney, conducted all the testing and analysis. She has graduated from the university with a Master of Science degree specializing in Human Factors.

“No matter how often pilots have rehearsed actions to an event in a simulator, events in the real operating environment can present in confusing ways, leading to a temporary and potentially disorienting disruption of normal information processing,” O’Hare told PsyPost.

In the study, 22 general aviation pilots were tested in a flight simulator. They had a wide range of experience — from 15 to 2,050 flight hours.

The pilots first completed an orientation flight, in which they took off from a small rural air strip, flew for a few minutes, and then landed. After this, the pilots completed seven more flights.

Two of these flights included an aerodynamic stall and another two included an engine failure. During one of the stalls and one of the engine failures, the pilots were given a warning beforehand in a pre-flight briefing. In the other two cases, the abnormal flight event happened without warning.

The researchers recorded flight data, eye movements, and heart rate during all the simulator tasks.

The researchers found that the pilots’ heart rate increased during the expected engine failure, but it increased even more after the unexpected engine failure. Similarly, the expected engine failure resulted in an increase in pupil dilation, but the unexpected engine failure resulted in even greater dilation.

Kinney and O’Hare also found that the unexpected event impaired flight performance and visual scanning of the cockpit. No pilots crashed after the expected engine failure, but only 54.5% of the pilots landed safely after the unexpected engine failure.

Pilots tended to spend less time looking at the flight instruments and more time looking at the outside environment during the unexpected engine failure. They specifically spent less time viewing the airspeed indicator, altimeter, GPS map, turn coordinator, and directional gyro in the unexpected compared to the expected event.

The researchers found that pilots who landed safely after the unexpected engine failure tended to spend more time viewing the airspeed indicator, the attitude indicator, and the altimeter compared to those who crashed.

In contrast, Kinney reported in her master’s thesis that pilots spent more of their time looking at flight instruments during the unexpected stall compared to the expected stall, suggesting that they were “attempting to gather and process as much information as possible.”

In the unexpected stall, 30.8% of the pilots incorrectly pulled back on the throttle after hearing the stall warning and 38% of pilots did not lower the plane nose. None of the pilots pulled back the throttle during the expected stall and they all lowered the nose as required.

The researchers found that pilots who incorrectly pulled back on the throttle after hearing the stall horn spent longer looking at the flight instruments, while those who did not pitch the nose down spent significantly less time viewing the altimeter and the vertical speed indicator.

The former group may have recognized there was an abnormal event but diagnosed it incorrectly, while the latter group may have continued to fly towards their destination without initially recognizing there was even a problem.

Despite the importance of recovering from unexpected aviation events, there is relatively little scientific research on the topic.

“Experimental studies are still few and far between. We need to know much more about exactly what mechanisms are disrupted, and most importantly, how to prepare pilots for such eventualities. Much training involves preparing a response to a given event but determining exactly what the event is can often be challenging,” O’Hare said.