Pilot Workload: How to Measure It Objectively

What does workload mean in aviation?

Workload refers to the combined mental and physical effort that a phase of flight demands of the pilot. It depends on the situation (weather, traffic, a failure), but also on the pilot's experience and condition.

US certification rules for transport category aircraft describe it through the functions of the flight crew: flight path control, collision avoidance, navigation, communications, systems management and decision-making. Among other factors, they consider the degree and duration of concentrated mental and physical effort ^[6]. They do not, however, prescribe any physiological measure ^[6].

Subjective measures: the NASA-TLX

NASA built the NASA-TLX from 16 experiments, including aviation simulations. It combines six dimensions: mental demand, physical demand, temporal demand, perceived performance, effort and frustration ^[1].

It remains the reference because it is simple, quick and comparable from one study to the next. Its limitation lies in its nature: it is completed after the task. It depends on the pilot's memory and says nothing about the precise moment when workload peaked.

Physiological measures

Signals from the body make it possible to track workload continuously, without interrupting the flight. A systematic review of 58 studies examined cardiac, respiratory, skin, blood pressure and ocular measures. Its conclusion is clear: these measures are sensitive to workload, but none of them can discriminate it reliably on its own ^[2].

A more recent review focused on pilots, based on 29 studies, shows that heart rate responds to workload more clearly than heart rate variability indices, whose results remain inconsistent ^[3]. Many of these studies had 10 participants or fewer, and most were conducted in simulators ^[3].

EEG: what the research says

EEG records the brain's electrical activity directly. A review covering pilots and drivers reports that high mental workload goes with increased theta activity and decreased alpha ^[4]. Mental state detection systems reach accuracy of around 90% in offline analysis, but real-time detection remains difficult ^[4].

A 2022 meta-analysis, which includes flight simulation tasks, confirms that frontal theta power is the most robust EEG marker of cognitive load ^[5].

Why the measures should be combined

Every measure has blind spots. A questionnaire tells you what the pilot felt, not when. The heart responds to workload, but also to physical effort, stress and breathing. EEG is close to mental activity, but sensitive to artefacts.

Two independent signals moving together at the same instant are far harder to dispute than a single number. That is the SPARK AERO approach: reading workload from the brain signal, together with the scanning movements of the head and the flight events, on a single timeline. In the simulator, where scenarios and failures can be replayed, this makes it possible to compare sessions and track a student's progress.

Limitations and precautions

• Most studies are conducted in simulators, and often with small samples ^[3].
• Heart rate variability indices are influenced by breathing, which muddies their interpretation ^[3].
• Research findings describe group averages: tracking an individual pilot means comparing each measurement against that pilot's own baseline.
• No physiological measure is currently required by certification regulations ^[6].