Human Performance and Limitations in IFR/IMC Flight
IFR helicopter flying imposes a specific workload: sustained instrument scan, high communication load, and the need to manage automation while hand-flying. Candidates must understand the sensory illusions that matter in IMC, the limits of attention and workload, and the countermeasures.
Concepts to master
- Spatial disorientation: the somatogravic illusion (acceleration feels like a climb), the leans, and the Coriolis illusion during a head turn in a turn.
- Vestibular versus visual cues: in IMC, trust the instruments, not the seat of the pants.
- Workload and attention: task saturation, the narrowing of attention, and the value of a disciplined scan and callouts.
- Fatigue and circadian effects, especially on night IFR sectors.
- Decision-making: confirmation bias, plan continuation bias, and the value of a stabilised approach criterion.
- Stress and arousal: the inverted-U relationship between arousal and performance.
Common traps
Questions describe a pilot who feels a climb during acceleration and ask for the illusion name (somatogravic). Another trap is the assumption that a second pilot removes all risk: crew coordination only works with clear roles and callouts.
Rule of thumb
When the body and the instruments disagree in IMC, the instruments win; cross-check two independent sources before acting.
Worked example
On a night departure in IMC, the helicopter accelerates and you feel a strong pitch-up sensation. That is the somatogravic illusion. The response is to hold the attitude on the attitude indicator and cross-check airspeed and vertical speed, not to push the nose down on sensation.