The way pilots responded to a technical malfunction
resulted in the crash of Air Asia Flight QZ8501, investigators said Tuesday.
The ill-fated plane was en route to Singapore from the
Indonesian city of Surabaya on December 28 last year when it crashed into the
Java Sea, killing all 162 people on board.
The plane's flight control computer had a cracked solder
joint that kept malfunctioning. Aircraft
maintenance records found it had malfunctioned 23 times in the year before the
crash, and the interval of those became shorter in the three months prior to
the crash.
"Subsequent flight crew action resulted in inability to
control the aircraft... causing the aircraft to depart from the normal flight
envelope and enter a prolonged stall condition that was beyond the capability
of the flight crew to recover," Indonesia's National Transport Safety
Committee said in a report.
In other words, "it's a series of technical failures but
it's the pilot response that leads to the plane crashing.
The investigation, a joint effort involving Australian,
French, Singaporean and Malaysian authorities, point to weaknesses in pilot
training in dealing with upsets, or when an aircraft is angled greater than 45
degrees.
"Our recommendation to Air Asia is to train their
pilots flying the Airbus plane on how to make an upset recovery,"
investigator Nurcahyo Utomo said.
The Air Asia pilots had not been trained for that scenario,
he added, because the manual provided by the plane's manufacturer said the
aircraft, an Airbus 320, was designed to prevent it from becoming upset and
therefore upset recovery training was unnecessary.
Air Asia has since required upset recovery training for its
pilots, Utomo said.
Utomo also said the cockpit voice recorder showed confusing
instructions from the captain to the copilot who was manning the controls at
the time.
"The most interesting part that could be heard from the
CVR (cockpit voice recorder) is that whenever the plane went up the captain
said 'pull down'...To go down, the captain has to say 'push', while to go up,
the captain has to say 'pull' in reference to moving the side stick
handle."
"A huge amount of training is done on take off and
landing and traditionally of course is 70-80% (of when accidents take place),
only 10% takes part in the cruise phase of flight. But if something does happen
in the cruise phase of flight, it does typically end up fatal."
Preliminary findings from the NTSC earlier this year said roughly 35
minutes into the two hour flight, the pilot asked air traffic control for
permission to climb to avoid stormy weather.
The plane went from cruising at 32,000 feet, ascending
steeply to 37,400 in about 30 seconds -- something commercial planes are not
designed to do. It may have been climbing at a rate twice as fast as it could
and should, one analyst said.
Minutes later, the plane disappeared from radar.
Although the area was experiencing turbulent weather
patterns, seven other planes flying nearbylanded safely.
Malaysia-based Air Asia did not have the clearance to fly
the route on that particular day.
Indonesia's National Transportation Safety Committee issued
several recommendations to Air Asia, Airbus as well as Indonesian, US and
European aviation regulatory bodies but the statement did not detail what they
are.
The crash is one in a string of aviation disasters,
including the mysterious disappearance of MH370, to occur in
Southeast Asia.
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