Most pilots are aware that
carbon monoxide (CO) is a colorless, odorless and tasteless gas contained
in exhaust fumes. It is also a common by-product of chemical reactions
which can occur upon heating of many petroleum products and silicone-based
synthetic lubricants used as aircraft oils and hydraulic fluids.
The carbon monoxide level
in blood is measured through a specific blood-gas method and is reported
as a percentage. The normal level of carbon monoxide produced by the
body's metabolism is from 0.4-0.7%, but heavy smokers can have much
higher levels. Elevated levels of carbon monoxide in the bloodstream
can create the effects of hypoxia (oxygen deficiency). Here is one air
carrier crew's experience with CO:
- An electrical/hot
plastic smell was noticed in the cabin, and the Flight Attendants
reported feeling ill. Maintenance could not find any source of the
odor. We started boarding passengers, but boarding was suspended when
the odor returned. The Flight Attendants later went to the hospital...they
had carbon monoxide levels of [up to] 1.2 [%]. Later that evening,
the First Officer and I were tested for carbon monoxide and had levels
of 0.5 [%] and 0.6 [%].
Several hydraulic leaks were discovered in the engine thrust reversers
and in the tail cone. The APU was contaminated with hydraulic fluid
as well as the air conditioning system.
Headaches and nausea were
the symptoms reported by another crew who suspected carbon monoxide
exposure.
- After
climb we noticed an unusual, faint odor in the cockpit. We tried to
determine what the source of the odor might be. In the logbook, we
found a previous write-up of an undetermined "ozone" smell
in the aircraft. There were also two previous write-ups in reference
to unexplained smoke detector activation in the lavatories.
The First Officer said he was not feeling well. I was also slightly
nauseated, had a headache, and was extremely fatigued. Both Flight
Attendants also complained of the same symptoms. After arrival, we
all agreed we should seek medical attention. It was 3-1/2 hours after
the flight arrived that we had blood drawn. The [carbon monoxide levels]
ranged from 2.3 [%] to 2.5 [%]. I am aware that these values are above
normal. I wonder what the values might have been if the tests were
taken just after we landed.
The source of the odors was
not identified, but carbon monoxide probably caused the crew's symptoms.
More information about hypoxia and carbon monoxide can be found in the
Aeronautical Information Manual--Medical Facts for Pilots, Section 1,
Para. 8-1-2 and 8-1-4.
Handy
Detectors
A General Aviation pilot,
thwarted by closed airport restaurants, initially thought that his nausea
and dizziness during flight were due to skipping breakfast.
- I remember
not being able to find my approach plates, even though they were on
the floor beside me. I tried three times to set my destination into
the GPS. I was confused as to what to do and panic began to set in.
Fortunately, I was able to acquire the airport and complete the approach
visually. Upon landing, I discovered that my carbon monoxide detector
was jet black! I now suspect my disorientation was a result of carbon
monoxide exposure.
Aviation supply shops have
no "missing breakfast detector" available at any price. However,
small, lightweight carbon monoxide detectors are available for less
than $10, and change colors to inform aircraft occupants of the presence
of this odorless gas.
The
Air Up There Is Rare
Another General Aviation
pilot used oxygen delivered by nasal cannula to fend off altitude-related
hypoxia.
- During
a test flight, I received a clearance to climb and maintain FL250.
I was using supplemental oxygen. After about 20 minutes, I began to
experience hypoxia, but I had no awareness of it at the time. This
resulted in loss of altitude control by as much as 2,000 feet. Center
asked me to report my current altitude, which I was unable to do due
to mental confusion and inability to read my altimeter. I was given
a clearance back to my home base. I wrote it down, but was unable
to read it. With difficulty, and assistance from Center, I managed
to descend to a lower altitude. I violated clearance limits more than
once on the way down. Center was not happy. I neither felt the need
for, nor requested, any assistance from Center. I now realize I was
in serious trouble with acute hypoxia.
The reporter believes that
the oxygen flow rate may have been inadequate for the altitude flown.
A full-size face oxygen mask might have provided more reliable delivery
of correct amounts of oxygen. This reporter and other pilots of unpressurized
aircraft that fly at high altitudes might consider high-altitude pressure
chamber training, offered by the Air Force and the FAA. Hypoxia recognition
is a beneficial by-product of this training. Information and application
forms for this training may be obtained from local FAA Flight Standard
District Offices. Courses are offered for small fees at appropriately
equipped Air Force bases.
Wisdom
From Weekend Warriors
An airline Captain traded
his regular "office in the sky"the automated cockpit
of a passenger jetfor weekend flying in a high performance single-engine
aircraft. Lesson learned: "Twenty years of airline operations are
not necessarily good training for being a weekend warrior in a light
plane!"
- I was
flying our Bonanzaa recent purchase. We could have gone IFR,
but I desired some flexibility maneuvering through an area of rain
showers. Weather reports and forecasts indicated we could [go VFR].
We were on top of a scattered-to-broken layer at 4,500 feet, with
seemingly good visibility. My perceptions were misleading, as in an
instant we were in the soup. I was surprised and frustrated, as cheating
VFR is not something I condone. I advised Center that we were unable
to maintain VFR and were making a 180 degree turn.
I am a Captain for a major airline. My background is General Aviation.
I know better. The decision to go VFR should have been determined
by the weather alone, and while VFR appeared do-able, it was not certain.
This Bonanza is a lot harder to fly than the B-757 I drive at work.
Many of the judgement/decision-making factors are totally different.
I'm having to dust off operating rules that have been on the shelf
for a while.
"Rattled" is the
description another pilot used to describe to ASRS the results of a
nighttime GA flight over a densely populated area. This high-time ex-military
and air carrier pilot had fewer than 100 hours of GA flight experience,
and had joined a local flying club only two days prior to his first
cross-country flight--which he elected to make at night, although severe
turbulence had been forecast and reported.
- Experienced
the worst turbulence in 36 years. Shoulder and lap belts were tight,
I still got my head banged off the top of the canopy. Lasted about
5 seconds, aircraft was tossed around like a bird in a jet blast,
lost 900 feet...was unable to change frequency to Tower. By the time
I contacted them I was in their Class D airspace at 2,000 feet in
the departure corridor for the active runway. They mentioned that
to me and cleared me for a left downwind to Runway 29L. I was somewhat
rattled, had asked for a right downwind entry for Runway 29R, that
is what I heard, and that is where I headed. The Tower corrected my
error with no small amount of frustration in the voice. I landed,
the taxi was uneventful.
Corrective actions? Our reporter
thought of many--after the fact:
- I thought
I was familiar with the aircraft's navigation technology, but was
not. The little "To" and "From" thing [flag] will
forever be prominent.
- Contacting
the Tower earlier.
- The aircraft
has three places to set up future frequenciesuse them.
- Get more
dual time in unfamiliar environments.
Won't Kick, Does Bite
The
FAA shows hand-propping horror movies at Safety Seminars, and provides
grim anecdotes of pilots who were sure they could hand-prop with impunity.
One such example involved a Cessna which wiped out four (4!) tied-down
aircraft before it was halted in its rampage by running into a hangaron
the opposite side of the airport!
The owner of the Aeronca
Champ who reported a runaway aircraft experience to ASRS was at least
somewhat aware of the airplane's propensity to take off solo, for he
sought the assistance of a non-pilot. But the man was not equal to the
thrust force of a Champ:
- Attempted
to prop-start the airplane using a safety person to stand in front
of the horizontal stabilizer and hold the tail. Upon starting, the
airplane surged forward and turned into a C-172 parked on the ramp.
The person at the tail was not qualified in the aircraft or to prop-start
the airplane. Single-pilot prop starts can safely be accomplished
only by having the tail securely tied down.
A proven safe technique for
hand-propping starts is to tie down the aircraft, securely chock the
main gear, and have a competent person in the cockpit standing on the
brakes.
Chock-A-Prop
A corporate pilot reports
another incident of damage by props, this one induced by misplaced chocks.
- After
getting permission to taxi, we had to wait for a line person who was
trying to park another aircraft on our right side. The other aircraft
did not park where directed, and the line person ran down to where
it was trying to park. When the line person left, she put down the
chocks she had in her hand, only she left them standing on end, to
the right of my right engine nacelle, where they were out of my line
of sight. As I turned right out of my parking spot to taxi, my right
prop caught the chock and tossed it into my nose landing gear door,
denting it. An A&P mechanic found the damage was only cosmetic.
A contributing factor was the chocks...standing on end instead of
flat, where the props would have passed over the top of them.
Safe operating procedure
for the line person should include not leaving chocks unattended and
out of their usual position near a running aircraft. However, the reporter
could have assured a safer taxi by waiting for an "all clear"
or other definitive signal from the line person.
