effects, including reduced mental capacity, dizziness,
confusion, an increased heart rate, and rapid breathing.
Meeting the Challenge
Meeting the human factors challenges of high-altitude
flight begins with an understanding of the problems
outlined above. The next step is to take the proper
precautions to reduce the risks of hypoxia, cold stress,
and dehydration.
For those fortunate enough to be
flying pressurized aircraft, proper
operation of the pressurization
system and attention to cabin
altitude are essential to avoid cabin
conditions conducive to hypoxia.
For those flying unpressurized
craft, the most obvious way to
avert the problems of hypoxia is
through the use of supplemental
oxygen. Even if your aircraft isn’t
equipped with an oxygen system,
portable systems are available that
can be easily configured and used
when needed. To provide a greater
degree of safety, consider following
the requirements of FAR 135, even
when flying under Part 91. In short,
FAR 135. 89 (Pilot Requirements:
Use of Oxygen) requires pilots to
continuously use supplemental
oxygen when operating “( 1) at
altitudes above 10,000 feet through
12,000 feet MSL for that part of the
flight at those altitudes that is of
more than 30 minutes duration; and
( 2) above 12,000 feet MSL.” Pilots
are encouraged to use supplemental
oxygen whenever flying at night at
altitudes of 5,000 MSL or higher, or
any time they suspect they may be
subject to the effects of hypoxia.
Understanding the effects
of density altitude on aircraft
performance is a critically important
aspect of flying, but just as important
is the knowledge and understanding
of how altitude affects human
performance. By knowing the
symptoms of hypoxia and other
high-altitude maladies, we can be
better prepared and enjoy a higher
level of safety when flying at higher
altitude.
Robert N. Rossier has been flying for more than 30
years. A former aerospace engineer and flight school
manager in Colorado, he spent 12 years flying for a
small airline/charter service in the Northeast, serving
as chief pilot and check airman. He has been writing
for the aviation industry for nearly 20 years and was
the recipient of a 2001 Aerospace Journalist of the
Year Award.
