EASA ATPL — Human Performance (040) Exam Prep

Correct answer: B. 5,000 to 10,000 ft — night vision degrades above approximately 5,000 ft, and cognitive effects appear above 10,000 ft

Hypoxia effects begin at surprisingly low altitudes. Night vision (rod cell function) begins to degrade above approximately 5,000 ft cabin altitude due to reduced retinal oxygen. Between 10,000 and 15,000 ft, judgement, memory, and calculation ability deteriorate. The insidious nature of hypoxia means the affected person often feels a sense of well-being (euphoria) and is unaware of their impairment. Time of Useful Consciousness (TUC) at 25,000 ft is only about 3–5 minutes.

Correct answer: B. A sub-threshold roll rate that goes undetected by the semicircular canals, followed by a correction that IS detected, creating the false sensation of rolling in the opposite direction

The leans is the most common form of spatial disorientation. It occurs when a gradual, sub-threshold roll goes undetected by the semicircular canals (which only detect angular acceleration above a certain threshold). The pilot unknowingly enters a bank. When the bank is noticed and corrected with a more abrupt roll back to wings level, the semicircular canals DO detect this correction and create the sensation of rolling in the opposite direction. The pilot then feels an compelling urge to lean back into the original bank.

Correct answer: B. That accidents result from multiple failures aligning across several defensive layers (organisational, supervisory, preconditions, unsafe acts)

James Reason's Swiss Cheese Model illustrates that in complex systems, multiple layers of defence (like slices of Swiss cheese) exist to prevent accidents. Each layer has holes (latent failures, active errors). An accident occurs only when the holes in multiple layers momentarily align, allowing a hazard to pass through all defences. The model emphasises that accidents are rarely caused by a single failure but by a chain of contributing factors at organisational, supervisory, precondition, and individual levels.

Correct answer: C. 13 hours

Under EASA Part-ORO Subpart FTL (ORO.FTL.205), the maximum basic FDP for a two-pilot crew depends on the reporting time and the number of sectors. For an early start at 07:00 with 1–2 sectors, the maximum FDP is 13 hours. This decreases with later reporting times (due to circadian low) and with more sectors. Extensions are possible with in-flight rest or augmented crew, but the basic maximum for an 'acclimatised' crew in the early morning window is typically 13 hours.

Correct answer: B. Nitrogen dissolved in body tissues comes out of solution as gas bubbles when ambient pressure decreases rapidly

Decompression sickness occurs when dissolved nitrogen in body tissues comes out of solution and forms gas bubbles due to a rapid decrease in ambient pressure. The risk is greatest when ascending to high altitude after diving (Henry's Law: gas solubility is proportional to pressure). Symptoms include joint pain ('bends'), skin tingling ('creeps'), respiratory distress ('chokes'), and neurological symptoms. This is why a minimum surface interval of 12–24 hours is recommended between scuba diving and flying.

Correct answer: C. 02:00–06:00 local time (Window of Circadian Low, WOCL)

The Window of Circadian Low (WOCL) occurs approximately between 02:00 and 06:00 local time (with respect to the individual's acclimatised time zone). During this period, core body temperature is at its lowest, alertness is minimal, reaction times are longest, and the risk of microsleeps is highest. EASA FTL rules account for this by reducing maximum FDP when duties encroach on the WOCL. A secondary dip occurs in the early afternoon (post-lunch dip) but is less severe.