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Asian Journal of Multidimensional Research (AJMR)
https://www.tarj.in
332
AJMR
cruising for some time at 12,500 feet and subsequently found himself experiencing symptoms of
hypoxia. Most pilots are aware of the need for supplemental oxygen at higher altitudes, but may
decide that they can manage without it at altitudes around or just over 10,000 feet. While these
operations may be legal, pilots should be aware of the wide variation in individual responses to
flight at these altitudes.
Hypemic hypoxia occurs when the oxygen-carrying capacity of the blood is reduced. Sufficient
oxygen at adequate pressure is present in the inhaled air, but the oxygen molecules do not bind to
the hemoglobin in the blood. Carbon monoxide poisoning is a common cause of this condition.
Carbon monoxide binds to the blood hemoglobin about 200 times more easily than oxygen and
prevents the oxygen molecules from attaching. Exhaust fumes from the engine or from a cabin
heater are the most common source of carbon monoxide in the cabin. Carbon monoxide is
colorless and odorless, and thus is difficult to detect. Fortunately, inexpensive carbon monoxide
detectors are now readily available that will alert the pilot to the presence of this dangerous gas.
Hypemic hypoxia may also be caused by blood donation. In that case there are simply not
enough red blood cells present in the blood stream to pick up the oxygen. The effects of blood
donation may last several weeks.
Like happiness, fatigue can be a hard thing to define. The dictionary (Merriam-Webster Ninth
New Collegiate Dictionary 1985) defines fatigue as “weariness or exhaustion from labor,
exertion, or stress”. The FAA defines fatigue as “… a condition characterized by increased
discomfort with lessened capacity for work, reduced efficiency of accomplishment, loss of power
or capacity to respond to stimulation, and is usually accompanied by a feeling of weariness and
tiredness”
1
. Many people associate fatigue with sleepiness, but fatigue is not just being sleepy.
This distinction is made by Shen et al. who noted that “Sleepiness and fatigue are two
interrelated, but distinct phenomena”
2
. Arguably, pilots seldom become fatigued in the same way
as a person who has just completed a 10-km race. However, other aviation workers, such as
aviation maintenance technicians, might well experience fatigue with no sleepiness component
after completing some physically-demanding tasks. Nevertheless, fatigue and sleepiness are
often used interchangeably, and the research literature, at least that dealing with aviation, has
largely ignored aspects of fatigue other than sleepiness. Therefore, while the distinction between
fatigue and sleepiness is recognized, the discussion in this section is limited to sleepiness.
In 1990, the National Transportation Safety Board
3
(NTSB) added “Reduce Accidents and
Incidents Caused by Human Fatigue” to its list of most wanted safety recommendations. This
arose out of a series of accidents in which fatigue (usually, lack of sufficient, timely sleep) was
indicated as a factor in the crash. This was typified by the crash of a cargo DC-8 on approach to
Guantanamo Bay, Cuba on August 18, 1993. The NTSB found that the probable cause of the
accident was, “The impaired judgement, decision-making, and flying abilities of the captain and
flight crew due to the effects of fatigue”
4
. In this case, the flight crew had experienced a
disruption of circadian rhythms and sleep loss, after being on duty for 18 hours and having flown
9 hours at the time of the accident. Following that recommendation, many air carriers
implemented policies to improve the rest of their crew. However, pilot fatigue continues to
appear as a factor in accidents as illustrated by the fatal Colgan Air crash in Buffalo, New York
on February 12, 2009. In that case, the NTSB concluded that “… the pilots’ performance was
likely impaired because of fatigue”
5
. This crash also highlighted the importance of considering
not just the time a pilot is on duty, but also what they are doing in the hours leading up to a
flight. In the case of the Colgan crash, pilots’ commuting practices may have contributed
ISSN: 2278-4853 Vol 10, Issue 9, September, 2021 Impact Factor: SJIF 2021 = 7.699
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