Article written by World Champion Canopy Pilot and Jump Pilot, Andrew Woolf.
What is Hypoxia?
Hypoxia, often misunderstood as merely a lack of oxygen in the brain, is actually the condition where there is insufficient oxygen in the body’s tissues. Altitude causes this effect as the reduction in air pressure means insufficient oxygen is being forced into the tissues. While its most noticeable effects are slower reaction times and poor decision-making, hypoxia can also cause confusion, restlessness, and an increased heart rate. In aviation, these symptoms can lead to serious safety risks, as a pilot experiencing hypoxia may struggle with critical tasks or misinterpret important information.
Various factors can influence how quickly hypoxia affects an individual. Physical fitness, smoking habits, and acclimatisation to altitude all play a role. Individuals in good physical condition, who do not smoke or are used to high altitudes, may experience delayed onset of hypoxia compared to those who are unaccustomed to such conditions.
Time of Useful Consciousness
The Time of Useful Consciousness (TUC) is the time from the interruption of normal air supply to the point where a person can no longer perform useful tasks. At this point, the individual is incapable of taking corrective or protective actions. According to the TUC chart, at flight level (FL) 150 (15,000 ft), the TUC is approximately 30 minutes. The science behind TUC helps explain the reasoning used to develop the regulations in CASR (Civil Aviation Safety Regulations) Part 91. This is why Jump Pilots experiencing extended Air Traffic Control (ATC) holds may decide to temporarily descend to a lower altitude, allowing pilots and skydivers to avoid the effects of hypoxia and maintain full awareness.
For parachute operations, many drop zones target a FL of 150 (15,000 feet) as the usual planned exit height. Regulations in CASR Part 105 8.03 and Part 91 Division 26.11 require that for operating at altitudes above FL125 (12,500 feet) but below FL140 (14,000 feet) for more than 30 minutes, all flight crew must use supplemental oxygen. While operating at any altitude above FL140, oxygen is required at all times. For the skydivers onboard, oxygen must be used at FL150 and above. These regulations are crucial in mitigating the effects of hypoxia, particularly for the pilot when multiple loads are planned throughout the day, compounding the potential effects.
Staying Aware
Hypoxia can be subtle when it begins to affect the body, and signs might go unnoticed or happen unexpectedly if fatigue from a busy day of high altitude exposure is already in play. It is important for pilots and skydivers to understand how to recognise these early signs and act accordingly.
Skydiving aircraft planning on operating at higher altitudes are equipped with oxygen systems for pilots’ use. Techniques such as donning the oxygen mask at the same altitude each time and also starting a timer when climbing through 10’000 feet will help ensure the pilot is aware of their exposure, and the exposure of skydivers on board, to hypoxia. Equally important is creating a culture where pilots and skydivers feel comfortable discussing their physical and mental states during the days operations, as fatigue can also make a person suffer hypoxia earlier than would be expected.
Strict adherence to oxygen-use regulations at high altitudes is essential to the safety of parachute operations. There are many examples of pilot errors associated with hypoxia, and the repercussions of a jump pilot losing consciousness could be catastrophic for everyone onboard. Also a jumper affected by hypoxia is a danger to themselves as well as their fellow skydivers. Following these regulations and being situationally aware of your altitude exposure minimises the risk of hypoxia and consequently improves safety.
Aviation is an industry where continuous learning is vital. By promoting a culture of safety and education, skydiving clubs not only improve operational effectiveness but also create a safer and more enjoyable environment for everyone involved. Pilots and DZ Safety Officers understanding and promoting awareness of hypoxia risks and adhering to established safety protocols will help elevate the safety standards of the skydiving community.
Article written by World Champion Canopy Pilot and Jump Pilot, Andrew Woolf.
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[Photo sources: Norman Kent Productions]