FAA Airline Transport Pilot (ATM)Human Factors and CRMMedium
A relief pilot on a long-haul flight wakes from a scheduled rest period just 20 minutes before top of descent and immediately returns to the flight deck. Although he feels generally rested from the flight, he experiences grogginess and struggles to process checklist items quickly. This performance decrement is best explained by which phenomenon?
- ASleep inertia
- BHypoxic hypoxia
- CSomatogravic illusion
- DWindow of circadian low
Show answer & explanationAnswer & explanation
Correct answer: A. Sleep inertia
Sleep inertia is the temporary grogginess and cognitive impairment experienced immediately after waking, even from a short nap, and typically lasts 15-30 minutes. It is distinct from circadian low, which relates to time-of-day alertness dips rather than waking transition.
Why the other options are wrong
- B. No indication of altitude or oxygen deficiency in the scenario.
- C. Somatogravic illusion involves misperceived pitch attitude from acceleration, not grogginess.
- D. Circadian low relates to a specific time window (roughly 0200-0600), not the act of waking itself.
Sleep Inertia
A period of impaired alertness, cognitive performance, and grogginess immediately following awakening, especially after being roused abruptly from deep sleep.
- Lasts typically 15-30 minutes but can extend longer
- Worse when awakened from deep sleep stages
- Common risk for relief/augmented crew after in-flight rest
- Mitigated by allowing adequate wake-up buffer time before duties
Memory trick: Groggy on waking? That's sleep inertia, not circadian low