AOPA Pilot Magazine - December 2024 - 83

he did not express concern or declare
an emergency. Three minutes later,
N9622T checked in with Lubbock
Tower and was cleared to land.
At 3:57, the tower controller
issued a low altitude alert:
" Centurion Two Tango check your
altitude immediately, the minimum
vectoring altitude in your area is
5,200 feet. "
The pilot mentioned autopilot
problems but the controller again
instructed the Cessna to climb to
5,200 feet and advised, " There is
an antenna at 12 o'clock a mile and
a half. " The pilot of N9622T read
back the climb to 5,200 feet, and
the tower reissued the climb and
altitude instructions. A minute later,
the tower advised, " Low altitude
alert, Centurion Two Tango check
your altitude immediately, the MVA
is 5,200 feet...Centurion Two Tango,
radar contact lost. " There was no
further communication.
Analysis
Self-induced pressure, faulty maintenance,
weather, and aircraft
limitations played a key role in this
accident. That morning, several
friends-including the pilot's girlfriend-expressed
concern about
icing conditions forecast along the
route and they attempted to persuade
the pilot to postpone the flight.
But the pilot insisted that he wanted
to beat the weather and would stay
farther south to avoid the conditions.
While fueling the Cessna 210,
the Belen airport employee questioned
the pilot about departing
in worsening weather. He told
investigators something seemed
off with the pilot that morning,
that he seemed fatigued. That and
worsening weather conditions had
prompted him to ask the pilot if he
was sure he should be flying, but he
had responded that he was OK, he
was heading down home to Texas.
The Cessna's maintenance
logbook showed the exhaust system
had been inspected during
the last annual inspection-about
seven flight hours before the accident
flight-and the airplane was
determined to be in an airworthy
condition. However, an examination
of the airplane revealed that
the cabin air heat exchanger contained
cracks in the metal barrier
that separates the engine exhaust
gas and the cabin air. These cracks
exhibited corrosion and deposits
on the surface consistent with having
been there before the accident,
allowing exhaust fumes to enter the
cabin and expose the pilot to carbon
monoxide (CO) poisoning.
Odorless, tasteless, and colorless,
CO is hard to detect and
extremely dangerous as it impairs
judgment and decreases a pilot's
ability to control the airplane.
Unfortunately, N9622T did not have
CO detectors installed.
During the earlier flight from
Nebraska to Belen, the pilot had
climbed the Cessna to 11,000 feet
msl to avoid a smoke layer en route.
The symptoms he described after
the flight and throughout the weekend
were similar to CO poisoning.
With cold outside temperatures
during the accident flight, the
pilot would have certainly used
cabin heat. The insidious nature
of CO poisoning again likely led to
impaired decision making before
and during that flight-especially
noticeable in his response to experiencing
freezing rain.
Precipitation in the accident
region was very light, and light
accumulating freezing drizzle was
reported at the surface. The area
was covered by a center weather
advisory and airmets that warned of
freezing rain, freezing drizzle, light
snow, and moderate or greater icing
conditions. At 3:53 p.m., Lubbock
Airport's METAR showed the wind
from 020 degrees at 15 knots with
gusts to 21 knots. The visibility was
4 miles in light freezing drizzle and
mist. The ceiling was overcast at
700 feet agl. The temperature was
minus 4 degrees Celsius with a dewpoint
of minus 5 degrees Celsius.
When the pilot reported an autopilot
issue during the approach, it was
likely that the airplane had accumulated
enough structural ice from
the freezing rain that the autopilot
couldn't function properly.
After N9622T crossed the intermediate
fix and turned inbound, its
groundspeed decreased gradually
from about 80 to 50 knots. Then
after crossing the final approach
fix at about 4,700 feet msl with a
48-knot groundspeed, the Cessna
made a sharp left descending turn
before impacting the ground.
Freezing rain's effect on airframes
is severe. When warm air
exists between two subfreezing
layers (as in a temperature inversion),
snow melts as it falls through
the warmer air. As the melted droplets
then fall into the subfreezing air
below, they become supercooled
and freeze on impact with an aircraft's
surface.
Investigators found numerous
chunks of ice in the wreckage
near the wings and still attached to
some of the airplane's leading-edge
surfaces. The ice chunks-ranging
in size from one to two inches
thick and two to five inches long-
were concave shaped and featured
a smooth surface on the inside of
the curve.
The NTSB's probable cause
cited the pilot's improper decision
to fly into icing conditions with a
non-FIKI approved airplane and
subsequent structural icing and loss
of control, the pilot's impairment
from CO poisoning, his self-induced
pressure to complete the flight, and
faulty maintenance. And, yes, all
those factors played a prominent
role in this accident. Sadly, as this
accident shows, several elements can
combine to forge an accident chain
that if left intact leads to unsafe decisions
and a dire outcome.
machteld.smith@aopa.org
airsafetyinstitute.org
AOPA PILOT / December 2024
83
http://www.airsafetyinstitute.org
AOPA Pilot Magazine - December 2024

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