Workload, stress and startle

When do extra tasks reduce useful performance?

Workload is the relationship between task demands and available resources.

Capacity depends on context

A routine task can become demanding when combined with fatigue, unfamiliar automation, time pressure or an abnormal event. Underload can also harm vigilance. There is no universal workload percentage or arousal curve that diagnoses a specific pilot’s safe capacity.

Manage the demand

Prioritise aircraft control, allocate tasks explicitly, defer non-essential work and seek time or assistance where appropriate. Moving from a highly automated mode to a more manageable level can help if it follows training and preserves control. Adding explanations during an urgent action may overload the receiving pilot.

Mechanism and limits

Stress is a response to perceived demands, while workload describes the demand placed on resources; they interact but are not identical. A competent pilot may face a high workload without distress, or feel stressed by uncertainty during a comparatively low task count. Acute stress can narrow attention and favour rapid familiar responses, which may help in one context and impede reasoning in another. Chronic strain can reduce recovery and readiness across duties. Effective controls therefore include both immediate task management and organisational support for recurring sources of strain.

Applied case · Buy time without losing monitoring

A synthetic late runway change arrives during preparation for departure. The change affects the route, performance, briefing and possibly configuration. Trying to edit everything while taxiing through a complex junction adds simultaneous demands. Where operationally appropriate, request time or stop at a suitable authorised position, allocate tasks and rebuild the affected checks under SOP. This changes the demand/capacity relationship rather than simply asking for more effort. The case does not prescribe a particular taxi action; it demonstrates why the team should protect aircraft control and surface awareness while managing a substantial plan change.

Why can an unexpected event delay a trained response?

Startle and surprise affect different parts of performance.

Reflex and mental model

Startle is an involuntary response to a sudden stimulus; surprise concerns a mismatch between events and the expected model. Either may disrupt attention and action selection. A memorised procedure may be available but not immediately retrieved if the crew interprets the event incorrectly.

Train recovery of a usable model

Scenario training should include varied cues, monitoring, communication and disciplined use of the approved response. After immediate safety actions where required, verify the situation and avoid fixation on the first explanation. The lab asks the learner to separate observation from interpretation before selecting the procedural path.

Mechanism and limits

A surprise can occur without a loud stimulus, for example when an automation reversion quietly produces an unexpected path. A startling sound can occur without a serious system failure. Distinguishing these concepts prevents training from equating drama with urgency. Immediate approved actions remain essential where specified, but the crew must also recover an accurate mental model. Scenario variation, clear control responsibility and concise communication can support that recovery. A strong emotional reaction is not proof of incompetence, and absence of visible alarm is not proof that the crew has understood the event.

Applied case · Separate the bang from the diagnosis

In a synthetic simulator event, a loud bang is followed by a yaw indication but no complete set of failure cues yet. A pilot immediately names a specific failure. That label may be right, but subsequent evidence still matters. Maintain the trained priorities and applicable immediate actions while verifying the indications and procedure selection. The lab offers observations separately from possible interpretations so the learner can see the leap. A second scenario uses a similar bang with different indications, showing why training one sound-to-action association is weaker than training recognition within the approved procedural framework.

Can you explain and apply the mechanism?

Four original questions. Work from the stated facts, then compare your reasoning with the explanation.