The captain of the AirAsia jet that crashed into the sea in
December was out of his seat conducting an unorthodox procedure when his
co-pilot apparently lost control, and by the time he returned it was too late
to save the plane, two people familiar with the investigation said.
Details emerging of the final moments of Flight QZ8501 are
likely to focus attention partly on maintenance, procedures and training,
though Indonesian officials have stressed publicly that it is too early to draw
any firm conclusions.
The Airbus A320 jet plunged into the Java Sea while en route
from Surabaya, Indonesia, to Singapore on December 28, killing all 162 people
on board.
It had been suffering maintenance faults with a key flight control computer for over a week, and one person familiar with the matter said the captain had flown on the same plane with the intermittently faulty device just days before the crash.
It had been suffering maintenance faults with a key flight control computer for over a week, and one person familiar with the matter said the captain had flown on the same plane with the intermittently faulty device just days before the crash.
AirAsia said it would not comment while the matter was under
investigation by the National Transportation Safety Committee (NTSC) of
Indonesia.
Reuters reported this week that maintenance problems on the
Flight Augmentation Computer (FAC), and the way the pilots reacted to them,
were at the heart of the investigation.
After trying to reset this device, pilots pulled a
circuit-breaker to cut its power, Bloomberg News reported on Friday.
People familiar with the matter told Reuters it was the
Indonesian captain Iriyanto who took this step, rather than his less
experienced French co-pilot Remy Plesel, who was flying the plane.
The outage would not directly upset the aircraft but would
remove flight envelope protection, which prevents a pilot from taking a plane
beyond its safety limits, leaving the junior pilot to fly the jet manually in
delicate high altitude conditions.
The decision to cut off the FAC has surprised people
following the investigation because the usual procedure for resetting it is to
press a button on the overhead panel.
"You can reset the FAC, but to cut all power to it is
very unusual," said one A320 pilot, who declined to be
identified. "You don't pull the circuit breaker unless it was an
absolute emergency. I don't know if there was one in this case, but it is very
unusual."
It is also significant because to pull the circuit breaker
the captain had to rise from his seat.
The circuit breakers are on a wall panel immediately
behind the co-pilot and hard or impossible to reach from the seated
position on the left side, where the captain sits, according to two experienced
pilots and published diagrams of the cockpit.
Shortly afterwards the junior pilot pulled the plane into a
sharp climb from which investigators have said it stalled or lost lift.
"It appears he was surprised or startled by this,"
said a person familiar with the investigation, referring to the decision to cut
power to the affected computer.
The captain eventually resumed control, but a person
familiar with the matter said he was not in a position to intervene immediately
to recover the aircraft from its upset.
Data already published on the plane's trajectory suggest it
may have been difficult for someone to move around the cockpit in an
upward-tilting and by then possibly unstable aircraft, but there is so far no
confirmation of the cockpit movements.
"The co-pilot pulled the plane up, and by the time the
captain regained the controls it was too late," one of the people familiar
with the investigation said.
Tatang Kurniadi, chief of Indonesia's NTSC, told Reuters
there had been no delay in the captain resuming control but declined further
comment.
Airbus declined to comment.
Lawyers for the family of the French co-pilot say they have
filed a lawsuit against AirAsia in Paris for "endangering the lives
of others" by flying the route without official authorisation on that day.
Investigators have said the accident was not related to the permit issue.
AirAsia did not immediately respond to requests for comment
on the lawsuit.
Although more is becoming known about the chain of events,
people familiar with the investigation warned against making assumptions on the
accident's cause, which needed more analysis.
Safety experts say air crashes are most often caused by a
chain of events, each of which is necessary but not sufficient to explain the
underlying causes of the accident
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