Aero-Tips!
A good pilot is always learning -- how many times have you heard
this old standard throughout your flying career? There is no truer
statement in all of flying (well, with the possible exception of
"there are no old, bold pilots.") It's part of what makes aviation
so exciting for all of us... just when you think you've seen it
all, along comes a scenario you've never imagined.
Aero-News has called upon the expertise of Thomas P. Turner,
master CFI and all-around-good-guy, to bring our readers -- and us
-- daily tips to improve our skills as aviators, and as
representatives of the flying community. Some of them, you may have
heard before... but for each of us, there will also be something we
might never have considered before, or something that didn't
"stick" the way it should have the first time we memorized it for
the practical test.
It is our unabashed goal that "Aero-Tips" will help our readers
become better, safer pilots -- as well as introducing our
ground-bound readers to the concepts and principles that keep those
strange aluminum-and-composite contraptions in the air... and allow
them to soar magnificently through it.
Look for our daily Aero-Tips segments, coming each day to you
through the Aero-News Network. Suggestions for future Aero-Tips are
always welcome, as are additions or discussion of each day's tips.
Remember... when it comes to being good pilots, we're all in this
together.
Aero-Tips 01.28.06
With the proliferation of turbocharged and turboprop airplanes
and the onset of personal jets, more and more of us will fly high
enough that we need extra oxygen, in the form of supplemental air
or pressurization. It’s critical to know not only when
we need supplemental oxygen or pressurization, but also what may
happen if our O2 system goes away.
Time of Useful Consciousness
Time of Useful Consciousness (TUC) is the amount of time a
person has from failure of the oxygen system to the point he/she is
so hypoxic that effective action is no longer possible.
For a “normal, healthy” pilot TUC varies as
follows:
-
Up to 20,000 feet, TUC averages five
to 12 minutes... plenty of time to recognize a problem and descend
to where natural air density is sufficient for extended
operation.
- At 25,000 feet, TUC drops to three to five minutes -- not much
time to recognize a failure and repair it, or descend.
- By 30,000 feet TUC is only one to two minutes, dangerous for a
solo pilot and hazardous even when you have crewmembers to help you
detect trouble.
- Take your new Very Light Jet (VLJ) to 40,000 feet and the TUC
is only nine to 15 seconds.
NOTE: The US Air Force prohibits flight
above 25,000 feet in the unpressurized T-37 jet specifically
because of the low TUC above that altitude.
ANOTHER NOTE: These numbers assume a
supplemental O2 malfunction or a slow pressurization leak. Rapid
decompression cuts them in half or more by sucking existing oxygen
out of your lungs.
Effective Performance Time
These “book” times take the pilot from “fully
functional” to “blubbering idiot” stage. When I
took FAA physiological training in an altitude chamber at Oklahoma
City I learned most people have an Effective Performance Time (EPT)
of about half the above values, in which they’ll be
functional enough to troubleshoot a balky O2 system or unstow, don
and engage an oxygen mask (if not the quick-don type). If
you’re a healthy nonsmoker, then, expect two to six minutes
to act from the beginning of an O2 interruption at 20,000 feet.
Smokers, the FAA told us, can cut about half the time off both
TUC and EPT. That makes it pretty dangerous for a smoker to fly
above 14,000 feet using supplemental oxygen or facing a leak in a
pressurized cabin higher up.
Aero-tip of the day: Just because an airplane
or an O2 system certified to operate at 20,000 or higher does not
make it safe to fly at those altitudes. You’ll learn a great
deal about O2 use and your personal symptoms of hypoxia by taking
an altitude chamber “flight.”