The Last Four Minutes of Air France Flight 447

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The crash of
Air France flight 447 from Rio to Paris last year is one of the
most mysterious accidents in the history of aviation. After months
of investigation, a clear picture has emerged of what went wrong.
The reconstruction of the horrific final four minutes reveal continuing
safety problems in civil aviation.

One tiny technical
failure heralded the impending disaster. But the measurement error
was so inconspicuous that the pilots in the cockpit of the Airbus
A330 probably hardly noticed it.

Air
France flight 447
had been in the air for three hours and 40 minutes
since taking off from Rio de Janeiro on the evening of May 31, 2009.
Strong turbulence had been shaking the plane for half an hour, and
all but the hardiest frequent flyers were awake.

Suddenly the
gauge indicating the external temperature rose by several degrees,
even though the plane was flying at an altitude of 11 kilometers
(36,000 feet) and it hadn’t got any warmer outside. The false reading
was caused by thick ice crystals forming on the sensor on the outside
of the plane. These crystals had the effect of insulating the detector.
It now appears that this is when things started going disastrously
wrong.

Flying through
thunderclouds over the Atlantic, more and more ice was hurled at
the aircraft. In the process, it knocked out other, far more important,
sensors: the pencil-shaped airspeed gauges known as pitot tubes.

One alarm after
another lit up the cockpit monitors. One after another, the autopilot,
the automatic engine control system, and the flight computers shut
themselves off. "It was like the plane was having a stroke,"
says Gérard Arnoux, the head of the French pilots union SPAF.

The final minutes
of flight AF 447 had begun. Four minutes after the airspeed indicator
failed, the plane plunged into the ocean, killing all 228 people
on board.

Few airline
crashes in recent years have subsequently unnerved passengers to
quite the same extent. "How was it possible that an Airbus
from such an apparently safe airline could simply disappear?"
they wondered.

Passengers
on the Rio-Paris route are still uneasy as they board their plane.
After the accident, the flight number was changed to AF 445. Many
frequent flyers have since opted for daytime flights across the
Atlantic because pilots can recognize storm fronts more easily during
the day.

Another large-scale
search for the stricken plane’s "black box" flight recorders
is due to begin in the coming weeks. Once again some 2,000 square
kilometers (800 square miles) of mountainous ocean floor will be
swept, some of it by a submarine from from the northern German city
of Kiel. "We shouldn’t speculate about the causes of the accident
until the search has been completed," says Jean-Paul Troadec,
the director of the French air crash investigation agency BEA.

Other experts
are less guarded in their comments. "We know pretty well why
the accident happened," says union boss Arnoux.

‘An Accident
Like This Could Happen Again’

Over the course
of several months of investigation, experts have gathered evidence
that allows them to reconstruct with relative accuracy what happened
on board during those last four minutes. It has also brought to
light a safety flaw that affects all jet airplanes currently in
service. "An accident like this could happen again at any time,"
Arnoux predicts.

Experts reconstructed
dozens of incidents involving Airbus planes to try to piece together
the puzzle of this particular disaster. Plane wreckage and body
parts give crucial clues as to what brought the plane down. Crash
investigators also conducted detailed analyses of the 24 automatic
fault messages that the aircraft sent to Air France headquarters
by satellite in the run-up to the accident. One particular message
– the very last one transmitted before impact – could solve the
mystery surrounding flight AF 447.

A half moon
lit up the Atlantic Ocean on the night of May 31, offering reasonably
favorable conditions for a flight through the dangerous intertropical
convergence zone. That’s where violent thunderstorms rage and columns
of thick clouds bar the way like an aerial obstacle course. In addition
to the on-board radar, the moon helps pilots identify dangerous
cloud formations and take appropriate measures.

On the night
of the tragedy, other planes diverted their flight paths and took
a detour around the danger zone.

Why then did
flight AF 447 head straight into the deadly storm system? Is it
possible that the tragedy began even before the plane took off?

Galeão
Airport, Rio de Janeiro, 6pm local time: Preparation for takeoff

Captain Marc
Dubois, 58, goes through the flight plan of AF 447: He enters a
starting weight of 232.757 tons into the on-board computer, 243
kilograms less than the maximum permissible weight for the A330.
As well as the passengers’ luggage, the ground crews load 10 tons
of freight into the cargo bay. Dubois has more than 70 tons of kerosene
pumped into the fuel tanks. That sounds a lot more than it actually
is, because the plane consumes up to 100 kilograms of kerosene every
minute. The fuel reserves don’t give much leeway.

Read
the rest of the article

March
1, 2010

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