KUALA LUMPUR, Jan 1 ― The captain of the Indonesia AirAsia Flight QZ8501 that crashed into the sea during a thunderstorm likely knew the lessons from the 2009 Air France plane crash, a pilot has said amid increasing focus on human error in the comparisons of both disasters.
Bill Palmer, an Airbus A330 captain for an unnamed major airline, wrote on US news network CNN yesterday that many parallels have been drawn between Flight QZ8501 and Air France Flight AF447, both of which encountered stormy weather, and noted that the latter plane’s airspeed-sensing probes had iced up before the jet plunged into the Atlantic Ocean, killing all 228 on board.
“In the aftermath of the Air France crash, in addition to an improved design of the probes, significant emphasis has been placed on pilot training on the prevention and recovery from similar scenarios ― such as loss of airspeed indications and high altitude stall recovery,” Palmer said in a commentary titled “How AirAsia flight compares to Air France 447 crash”.
“I would say all pilots, especially of Airbus aircraft, would be aware of AF447's lessons, including QZ8501's captain, given his reported experience,” he added.
UK daily The Independent reported yesterday that investigators will consider if pilot error had caused the crash of the Airbus A320 jet that disappeared Sunday with 162 people on board enroute to Singapore from Surabaya in Indonesia.
International newswire Reuters reported yesterday an anonymous source familiar with investigations into the air crash as saying that the plane made an “unbelievably” steep climb, which could result in the aircraft losing speed and then stalling, or losing lift and being unable to fly, and falling out of the sky.
According to AirAsia, Flight QZ8501 pilot Iriyanto, an Indonesian, had 6,100 flying hours under his belt.
Palmer said both Flight QZ8501 and Flight AF447 were lost in the thunderstorm areas of the Intertropical Convergence Zone (ITCZ).
The pilot noted too that both were sophisticated fly-by-wire Airbus jets, though different models, and that both passenger planes crashed at sea where debris drifted in the waters for days away from the point of contact before discovery.
“While flying into a thunderstorm is always to be avoided, it was not likely the sole cause of the accident. The reported requests by the crew to deviate course and change altitude seeking to avoided [sic] thunderstorm cells and turbulence are completely normal,” he said.
Media reports quoted Indonesia’s air navigation operator AirNav Indonesia as saying that the pilot had requested permission to raise the plane’s altitude to 38,000 feet from 32,000 feet at 6.12am local time Sunday.
Jakarta air traffic control gave approval two minutes later for the plane to ascend to 34,000 feet, but received no response from the cockpit.
Palmer said an Airworthiness Directive (AD 2014-25-51) released on December 10, 2014, in relation to Airbus A320 series aircraft, described how one could lose control of a plane in flight as a result of icing of the angle-of-attack probes and an interaction with the jet’s stall protection function.
According to the pilot, the aircraft’s system may be fooled into thinking that the plane is approaching a stalled condition ― though it isn’t ― when the probes freeze and the plane’s stall protections then pitch the aircraft’s nose down to recover.
“This erroneous pitch down cannot be overridden by the pilots unless an emergency procedure in the Airworthiness Directive is followed. All pilots flying this model airplane should be aware of this,” said Palmer.
“The procedure instructs the pilots to shut down two of the three air data computers to render the usual stall protection inoperative and allow recovery of the aircraft. Of course, there is no way, at this stage of the investigation, to know if this played a part, but investigators will certainly be looking for evidence of this phenomenon,” he added.
The pilot also noted that Flight AF447 had crashed in the deep Atlantic Ocean, where its depth of more than 12,000 feet and rough terrain on the seabed delayed recovery of the plane’s wreckage and flight recorders for two years.
Flight QZ8501, in contrast, crashed in the relatively shallow Java Sea off Borneo.
Searchers believe they have found the AirAsia plane’s fuselage lying on the seabed.
“Fortunately, the 100-foot depth of the Java Sea in the area where evidence of QZ8501 was found will almost certainly result in the relatively rapid location of the aircraft and recovery of the two flight recorders,” said Palmer.
“Clues from the way in which airplane parts were damaged on impact and the flight data and voice recorder contents will provide answers. But like any aircraft accident, the cause is likely to be the result of a chain of events and conditions, the absence of any one of which would have avoided this tragic accident,” he added.
Inclement weather has again hampered search and recovery efforts today; international newswire Reuters reported an aviation official saying it could take a week to retrieve Flight QZ8501’s two black boxes.