Carbon Monoxide: A Hidden Killer
by Paul Engstrom, Aviation Writer and IFA Member
Any one of numerous blunders that the pilot of a Piper
Cherokee made on a mid-winter night in Minnesota would have been
enough to doom his flight.
But what ultimately killed him and his passenger was
carbon monoxide poisoning.
On January 26, 1998, the pair were flying in fog and
mist from Brainerd to Owatonna. The pilot had all of three hours of
instrument and about six hours of night experience under his belt,
none of it solo.
And, according to
the National Transportation Safety Board’s accident report, the
Cherokee’s muffler—despite an inspection just two months earlier—was
rusty and pocked with tiny holes, allowing carbon monoxide from the
engine’s exhaust to enter the cockpit.
Indeed, an autopsy revealed that the pilot had a
carboxyhemoglobin level of 24 percent. Translation: Nearly one-fourth
of all the oxygen-carrying hemoglobin in his red blood cells was bound
instead to carbon monoxide, depriving his brain and body of
life-giving oxygen.
There are good reasons why carbon monoxide deserves a
prominent place in the Hall of Blame when it comes to insidious
general-aviation hazards:
-
The gas, a byproduct of incomplete combustion, is
odorless, colorless, and toxic even in small amounts.
-
Symptoms of carbon monoxide poisoning—nausea,
fatigue, headache, dizziness, and vision problems, among others—may
be mistaken for a cold, the flu, or indigestion.
-
You’re more susceptible if you smoke (in which case
your carboxyhemoglobin level already is 3 to 10 percent), you’re
old, or not physically fit.
-
Carbon monoxide bonds with hemoglobin 200 times more
readily than oxygen does, essentially bumping oxygen from its seat
in the bloodstream.
A number of sources may be to blame for carbon monoxide
exposure. Possible culprits are a crack in the heat muff or shroud on
the exhaust system that feeds the cabin heater, a leak between the
engine compartment and cockpit, a faulty exhaust-manifold gasket, even
exhaust from the aircraft taxiing ahead.
“Any leak in the exhaust system of an aircraft is a
real and present danger,” says Dr. Robert W. Carlson, an
instrument-rated pilot and professor of medicine at Stanford
University.
Does this mean pilots are at the mercy of carbon
monoxide? No. But it does mean paying special attention to the “P”
word— prevention. Namely:
-
Ensure the muffler is thoroughly examined by
mechanics at every 100-hour inspection. In the case of the Piper
Cherokee, the NTSB faulted mechanics for an “inadequate” muffler
check.
-
Abide by the Federal Aviation Administration’s
airworthiness directives, if any, regarding your exhaust system.
-
Consider installing a carbon monoxide detector in the
cockpit. But beware: Not all detectors live up to manufacturers’
claims and some have a short life span.
Fortunately, you can quickly and easily counteract
carbon monoxide exposure aloft. Simply turn off the cabin heat, open
the fresh-air vents or use supplemental oxygen if you have it, and get
on the ground as soon as possible.
When he isn’t
flying, Paul Engstrom writes and edits from Sebastopol, Calif.
The information contained herein is meant for
informational purposes only. Neither IFA, nor Paul Engstrom assume any
responsibility or liability for events that occur due to actions you
or others on your behalf take based on the information given in this
article. You are proceeding at your own risk. It is strongly advised
that you seek the opinion and advice of a qualified aviation medical
examiner and appropriate medical physician for any medical needs you
may have. |
