Confiabilidade humana - PCS5006


O acidente de Atenas

De: "Fragoso"
Data: Sex Set 9, 2005 1:10 pm
Assunto: Crew confusion found in Athens plane crash The crew members of a Cypriot airliner that crashed Aug. 14 near
Athens became confused by a series of alarms as the plane climbed,
failing to recognize that the cabin was not pressurizing until they
grew mentally disoriented because of lack of oxygen and passed out,
according to several people connected with the investigation.

Complicating the cockpit confusion, neither the German pilot nor the
young, inexperienced Cypriot co-pilot could speak the same language
fluently, and each had difficulty understanding how the other spoke
English, the worldwide language of air traffic control.

A total of 121 people were killed in the crash after the plane
climbed and flew on autopilot, circling near Athens as it was
programmed to do until one engine stopped running because of a lack
of fuel. The sudden imbalance of power, with only one engine
operating, caused the autopilot to disengage and the plane to begin
its final descent.

The Greek authorities have made cryptic statements hinting at oxygen
problems but have so far not announced the full findings of

The people interviewed for this article agreed to do so on condition
that they not be identified because none are official spokesmen for
the investigation and because of political sensitivities arising from
a Cypriot plane crashing in Greece.

Investigators pieced together the story of the crash from numerous
sources. In the wreckage, they found the first solid clues - the
pressurization valve and an air outflow valve set incorrectly. Air
traffic control tapes provided information on the confusion in the

The plane had a sophisticated new flight data recorder that provided
a wealth of information. There were maintenance records from the
night before, and investigators interviewed the mechanics who worked
on the plane.

Among other things, the investigators determined that the pilot was
not in his seat because he was up trying to solve a problem that
turned out to be not the greatest threat facing him.

The plane that crashed, a Boeing 737, underwent maintenance the night
before. The maintenance crew apparently left a pressurization
controller rotary knob out of place, according to the officials
connected to the investigation, and the crew did not catch the
mistake during preflight checks the next day. This meant that the
plane could not pressurize.

At 10,000 feet, or 3,000 meters, as designed, an alarm went off to
warn the crew that the plane would not pressurize. However, the crew
members mistakenly thought that the alarm horn was a warning to tell
them that their controls were not set properly for takeoff, the
officials said.

The same horn is used for both conditions, although it will sound for
takeoff configuration only while the plane is still on the ground.

The crew continued the climb on autopilot. At 14,000 feet, oxygen
masks deployed as designed and a master caution light illuminated in
the cockpit. Another alarm sounded at about the same time on an
unrelated matter, warning that there was insufficient cooling air in
the compartment housing avionics equipment.

The radio tapes showed that this created tremendous confusion in the
cockpit. Normally an aircraft cabin is held at 8,000 feet pressure,
so the crew at over 14,000 feet would already be experiencing some
disorientation because of a lack of oxygen.

During this time, the German captain and the Cypriot co-pilot
discovered they had no common language and that their English, while
good enough for normal air traffic control purposes, was not good
enough for complicated technical conversation in fixing the problem.

The crew members called the maintenance base in Cyprus and were told
that the circuit breaker to turn off the loud new alarm was in a
cabinet behind the captain. The captain got up from his seat to look
for the circuit breaker, apparently ignoring the confused co-pilot.

As the plane continued to climb on autopilot, the air grew so thin
that the crew became seriously impaired. The captain passed out first
on the floor of the cockpit, followed by the co-pilot, who remained
in his seat, according to the officials.

The autopilot did as it was programmed to do, flying the plane at
34,000 feet to Athens and entering a holding pattern. It remained in
a long circling pattern, shadowed by Greek military jets, until fuel
ran low and one engine quit.

Boeing, the maker of the plane, is-sued a notice shortly after the
crash to airlines that it would revise flight crew training manuals
to stress to crews that they must understand how the various warning
systems work and what to do about them.

The notice stresses that the takeoff configuration warning horn will
not sound under any circumstances after the plane has left the

The same horn will then be used only for a cabin altitude warning.
The company notice said there had been other instances of confusion
over the horn by pilots.

"Confusion between the cabin altitude warning horn and the takeoff
configuration warning horn can be re-solved if the crew remembers
that the takeoff configuration warning horn is only armed when the
airplane is on the ground," the notice said. "If this horn is
activated in flight, it indicates that the cabin altitude has reached
10,000 feet."