WHAT WENT WRONG
J. MAC MCCLELLAN
The so-called recoverable data module
is not an independent recorder such
as the FDR (flight data recorder)
installed in airline jets, but the flight
path, airspeed, altitude, and some
system data are recorded in electronic memory.
As the pilot climbed through 12,160
feet with a clearance to climb to flight
level 220 ( 22,000 feet), the recorder
indicated that he activated the oxygen
system that was installed in the SR22
at the Cirrus factory when the airplane
was built. The system supplied oxygen to
all four seating positions and was delivered with two clear masks and two green
masks. The green masks were equipped
with microphones. Nasal cannulas were
also supplied, but they are approved for
use only up to 18,000 feet.
The oxygen system in the Cirrus,
which is manufactured by Precise Flight,
was fed by a large 77-cubic-foot oxygen
cylinder. The system uses LED indicators to show the pilot the oxygen level in
the tank, and also to indicate when oxygen was required based on pressure
altitude, and a dedicated LED to indicate
a system fault.
Five minutes after the pilot activated
the oxygen flow, he was cleared to continue his climb to FL 230. The pilot
acknowledged the clearance, but the
Center controller noted that the pilot’s
voice had changed, and had taken on a
“helium/Mickey Mouse” quality, according to the NTSB.
About eight minutes later the controller noted that the pilot was climbing to
the wrong altitude and that in transmissions the pilot “was stepping all over
himself.” A few minutes later the pilot
was issued a vector to avoid traffic,
which he acknowledged, but his
response later when the controller
cleared him back on course was unreadable. However, the pilot responded to
another vector for traffic without difficulty several minutes later.
Twenty minutes after the controller
first noticed the change in the pilot’s
voice and his difficulty in communicating, the pilot requested a descent to
12,000 feet. The controller needed several attempts to confirm that it was the
Cirrus pilot requesting the descent
because the call sign was “unreadable.”
When the controller confirmed it was
the Cirrus asking for a lower altitude, he
issued a descent clearance to FL 240.
The pilot had not declared an emergency
or other urgency for his request, so the
controller was waiting for traffic separa-
tion to grant the request to descend to
12,000 feet. The pilot responded, but the
controller said he sounded “in distress
and out of breath.”
Two minutes later the controller
cleared the Cirrus pilot to descend to
12,000 feet and issued the altimeter
setting. The pilot acknowledged the
descent clearance and read back the
altimeter setting, but the airplane didn’t
descend from 25,000 feet.
Three minutes later the last
transmission from the Cirrus
pilot was received, but it
was only the pilot’s labored
breath, no spoken words.
For about the next six minutes the
controller attempted to contact the pilot
with no response. Finally, the pilot
replied with “go ahead,” and the control-
ler again issued the clearance to descend
to 12,000 feet and instructed the pilot to
“start your descent.” An airline pilot on
the frequency commented that the acci-
dent pilot sounded “incoherent.”
Three minutes later the last trans-
mission from the Cirrus pilot was
received, but it was only the pilot’s
labored breath, no spoken words. An
hour and 14 minutes later the Cirrus
flew directly over Eagle Creek at 25,000
feet and maintained its course and alti-
tude. Almost an hour later the recorded
data showed the engine parameters fluc-
tuating for about 30 seconds before
power indications and fuel flow dropped
to zero. The airplane then pitched nose
up and began a series of spiraling left
and right turns with pitch excursions in
both directions until the data stream was
lost. The recorded data indicated that
the oxygen tank was 29 percent full
when the Cirrus crashed.
