Piecing together the final moments of AirAsia flight
PUBLISHED ONJanuary 01, 2015 10:15 PMByKaramjit Kaur
It is unlikely that Indonesia AirAsia Flight QZ8501 exploded in mid-air, air crash experts say, as the first pieces of debris were spotted and some bodies recovered.
Chances are that the plane hit the Java Sea intact and broke up upon impact before plunging to the ocean floor.
The wreckage of the Airbus 320-200 was found more than 48 hours after the ill-fated flight, which left Surabaya for Singapore on Sunday morning with 162 people on board, went missing.
Search teams reported seeing some bodies intact.
An air force plane reportedly spotted a shadow of what looked like a plane on the seabed.
As the operations move from search and locate, to search and recovery, it would take weeks before enough pieces of wreckage and human remains are recovered for the authorities and investigators to determine how and why the crash happened.
Critical to this is finding the plane's black boxes which record conversations in the cockpit and preserve data on the position and speed of the aircraft.
But looking at what is known so far, there are several possibilities on what could have happened.
Retired United States airline pilot John Cox, who runs his own consultancy, said: "I am now seeing doors and reports of a large section located on the sea floor which are indicators, but not conclusive evidence, that the plane was in one piece when it hit the ocean.
"If the wingtips, nose and tail are found in the same area, then it will be conclusive that the plane was intact upon impact with the water."
Mr Jacques Astre, president of industry consultancy International Aviation Safety Solution, said: "The fact that the debris field is relatively small would suggest the aircraft broke up upon impact with the sea and not in flight."
If some bodies are found intact, it would suggest the same, said Mr H.R. Mohandas, a former pilot and now programme head for the diploma in aviation management at Republic Polytechnic.
Mr Astre added: "The close proximity of the debris field to its last known location also suggests the aircraft descended fairly quickly."
The area is about 10km from the aircraft's last known location over the Java Sea.
The first sign of trouble came about 45 minutes after the plane left Surabaya at 5.30am - an hour behind Singapore time - for the two-hour sector. At 6.12am, the cockpit requested permission from the Jakarta air traffic control to turn left to avoid a storm, which is common procedure when pilots encounter rough weather.
The pilot then asked to take the plane higher to 38,000 feet from its position at 32,000 feet, without explaining why.
The air traffic control decided to allow the plane to increase its height but only to 34,000 feet, because at that time another AirAsia flight was flying at 38,000 feet.
But when this was communicated to the pilot of QZ8501, there was no response from the cockpit.
Data from Indonesia's meteorological agency showed slight rain in the Belitung and Pontianak areas when the plane was estimated to be flying through the vicinity, with thick cumulonimbus clouds as high as 45,000 feet.
Such clouds can produce lightning and other dangerous weather conditions, such as gusts, hail and occasional tornadoes.
Mr Mark D. Martin, founder and chief executive officer of Martin Consulting, said: "In the unfortunate event of entering a cumulonimbus cloud at flight levels between 31,000 feet and 38,000 feet, it is common to see heavy updrafts and downdrafts, icing on control surfaces which can freeze corrective pilot actions, aggressive aircraft manoeuvres and the aircraft dramatically lose altitude in excess of 5,000 feet per minute."
A similar incident had occurred in June 2009 when Air France Flight AF447 plunged into the Atlantic Ocean, leaving no survivors, during a flight from Rio de Janeiro to Paris.
Official investigations concluded that the aircraft crashed after pilots failed to react correctly to temporary inconsistencies between air speed measurements.
This was likely due to ice crystals blocking the plane's pitot tubes, which measure air speed.
Mr Mohandas said: "It is possible that something similar happened to Flight QZ8501. In their attempt to avoid extreme weather conditions, the pilots could have taken some actions, including possibly initiating a climb which requires more power.
"This coupled with adverse weather conditions, including turbulence, and possibly the formation of ice on the surface of the aircraft at high altitude, could have disengaged the plane's auto-pilot systems."
He said: "With little or no visibility and without auto pilot, you don't know what's in front of you and the crew could have become disorientated. Under such circumstances, the plane could have gone into an uncontrolled descent."
With the wreckage found, experts can start piecing together the final moments of Flight QZ8501. To the relatives of those who perished, this may bring a sense of closure but, perhaps, no relief from the pain.
karam@sph.com.sg
This article was first published on December 31, 2014.
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