Metrotvnewscom, Jakarta: National Transportation Safety Committee (KNKT) Chief Soerjanto Tjahjono said the cause behind AirAsia Q8501 in December 2014 has similarities with Air France 447 Crash five years earlier.
"It is similar with Air France (447)," said Soerjanto, after press conference about investigation result of AirAsia crash, Jakarta, Tuesday (12/1/2015).
The investigation report indicates there are human factor behind AirAsia QZ8501 crash. Pilot cannot well respond the failure of rudder travel limiter unit (RLTU) and Flight Augmentation Computer (FAC) which mad the plane became stall and then crashed.
Air France 447 crashed in 1 June 2009 in the middle of journey from Rio de Janeiro, Brazil to Paris, France.
Investigation report issued by French aviation security agency, BEA, showed Air France 447 crashed because pilot failed to react effectively to problem with the plane's sensor.
"The technical aspects are different but there are similarities regarding pilot's reaction and confusion in the cockpit during problem," explained Aviation expert, Gerry Soejatman through phone.
Gerry explained bad response from the pilots could be caused by their reliance to auto-pilot system.
"They are seldom fly without auto-pilot. This is the debate. Auto-pilot makes flight cheaper but there is risk when problem happens," Gerry said.
Gerry said some airlines have implemented measures to minimize reliance to auto-pilot such as instruction to use manual mode within a certain period during flight. "As for AirAsia, i know they have implemented training in accordance with recommendation from KNKT so the pilot could respond better during problem," he said.
Unplugged Circuit Breaker?
KNKT revealed AirAsia QZ8501 faced four RLTU failures during its doomed flight. KNKT said the crash didn't happen because of weather or permit problem. The institution focused on the RLTU failures and respond of pilot to the problem.
It was revealed that the plane had repetitive RLTU problem. The plane's RLTU were error for 32 times in the last 12 months before it crashed.
During the doomed flight, the RLTU problem happened four times. The pilot was able to fix the first third faults according to the procedure. However in the fourth fault, Flight Data Recorder (FDR) retrieved from the plane recorded different indications.
The FDR showed the FAC was being reset causing auto-pilot and auto-thrust disengaged and the plane moved from normal law to alternate law. The problem in the FAC also caused the rudder moved two degrees causing the plane rolled.
KNKT suspected a person unplugged and then plugged the FAC's circuit breaker. However, KNKT admitted they don't have solid evidence about the action.
Gerry said the suspicion that pilot unplugged the circuit breaker cannot be proved. "Even KNKT said they cannot prove it. It cannot be concluded that pilot unplugged the circuit breaker," he said.
Lost in translation
Pilot briefly succeeded to control the plane from rolling but then it pulled up and entering prolonged stall which is impossible to recover.
KNKT found the co-pilot, Remy Emmanuel Plesel, pulled his stick when the plane stalled until it crashed.
Through the cockpit voice recorder (CVR), KNKT found the pilot, Captain Iriyanto, ordered plesel to 'pull down'. KNKT suspected Plesel thought he was asked to pull the stick whereas Captain Iriyanto most probably meant to push down the stick.
KNKT said FDR showed the plane pulled up in the same time with the order to 'pull down'.
Gerry said there is no formal procedure for communication in the cockpit. "There is no formal procedure for communication. There is still debate about relation between pilot and co-pilot," he said.
KNKT finished the investigation in 11 months. AirAsia QZ8501 crashed in Java sea in the journey from Surabaya to Singapore in 28 December killing 162 on board.
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