Sources: Crew's Inability To Understand Cockpit Warnings Or
Speak A Common Language May Have Spelled Flight's End
The cockpit crew aboard a doomed Helios Airways 737-300 was
confused by alarms and failed to recognize that the plane was
losing cabin pressure -- they succumbed to the lack of oxygen and
eventually lost consciousness. The aircraft crashed near Athens,
Greece, August 14th, killing all 121 people on board.
That's the story from unnamed sources close to the investigation
into the Helios disaster, as told to a reporter from the
International Herald Tribune.
The problem was further compounded, according to those sources,
by the cockpit crew's apparent inability to communicate. The pilot
was German, the copilot a Greek Cypriot and neither spoke good
enough English to communicate effectively in the international
language of aviation.
Eventually, the sources tell the Herald Tribune, one engine quit
because it ran out of fuel. The assymetric thrust caused the
autopilot to disengage and the aircraft plunged to the ground.
A Confusing Cacophony Of Warning Horns
The information cited by the paper's sources was gleaned from a
new-generation flight data recorder, along with records of a
maintenance check done the night before the aircraft went down. But
critically, investigators have reportedly finding a pressurization
valve and an air outflow valve in the wreckage -- both set
improperly. A pressurization control knob was turned to the wrong
setting during the previous night's maintenance, according to the
Herald Tribune sources. The cockpit crew didn't catch the mistake
during their preflight inspection.
When they heard an alarm in the cockpit as they crossed 10,000
feet, the paper reports both pilots assumed it was an improper
take-off configuration warning. Although the same horn is used for
both improper take-off configuration and to warn the crew that the
aircraft isn't being properly pressurized, the improper
configuration alert sounds only when the aircraft is on the ground,
those sources said.
When the aircraft passed through 14,000 feet, oxygen masks
dropped down in both the cockpit and the cabin. A master caution
light illuminated and, simultaneously, an alert sounded indicating
improper cooling in the avionics bay.
The cockpit confusion grew as the aircraft climbed on autopilot.
While both pilots could speak enough English to satisfy ATC
requirements, neither apparently possessed the language skills to
sort out the growing technical issues that would eventually lead to
their deaths, according to the report.
Why wasn't the pilot in his seat at the time of the crash? The
Herald Tribune reports he had gone to the back of the flight deck
to pull the circuit breaker for the avionics bay environmental
warning on the advice of ground crew members with whom the pilots
were talking on the radio. As the plane continued to climb, the
pilot passed out on the flight deck. The copilot collapsed in his
seat.
The 737 continued on autopilot to Athens, where it entered a
programmed holding pattern, shadowed by a pair of Greek F-16
fighters trying to figure out why the Helios flight was proceeding
NORDO. Eventually, one engine quit because of fuel exhaustion and
the final chain of events was set in motion, according to the
Herald Tribune's sources.
Boeing Rewrites The Book
Boeing, the plane's manufacturer,
has already promised to revise its manuals for the 737 to
strengthen admonitions to crew members: Know what warning is
sounding and why. In a notice to customers, Boeing pointed out that
the improper take-off configuration warning will only sound while
the plane is on the ground.
"Confusion between the cabin altitude warning horn and the
takeoff configuration warning horn can be resolved 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."