News
Indonesia AirAsia crash report raises questions about its answers
December 4th 2015
A faulty component and the crew's inadequate response caused Indonesia AirAsia flight QZ8501 to crash into the Java Sea en route from Surabaya to Singapore on December 28, killing all 162 people on board the A320, Indonesia’s National Transportation Safety Committee (NTSC) said on Tuesday. Read More » In their final report, the Indonesian investigators concluded poor maintenance and a “chronical” fault with the computer system that helps control the rudder's movement , the Rudder Travel Limiter (RTL), were major contributing factors to the accident, but so was pilot error.
Specifically, the NTSC report said a cracked solder joint caused the RTL to malfunction and send repeated warnings to the pilots. In response, the pilots tried to reset the computer, which in turn switched off the A320’s autopilot, sending the aircraft into a sharp roll and a stall from which they were unable to recover.
Officials said black box data suggested crew had "likely" shut off power to the computer that controls the RTL by pulling circuit breakers after three normal resets, using push buttons, failed to remove error messages. This was not usually done during flight, but the captain may have been influenced to try it after witnessing ground crew do it on the same plane three days earlier, the report said. To do so, the captain would have had to leave his seat, adding weight to the theory that he was not at the controls when the A320 began to lose control.
Investigators said they had asked Indonesia AirAsia and Airbus to take steps to prevent pilots "improvising" fixes to problems. It also said an Airbus manual on when to reset computers was "potentially ambiguous".
The report said there was miscommunication between the pilots as the plane plunged towards the sea, with the men at one point pushing their control sticks in opposite directions. Investigator Nurcahyo Utomo said that AirAsia pilots flying Airbus aircraft had not received adequate training for when their planes became severely destabilised, as it was not recommended by the manufacturer.
This Week in Asia-Pacific Aviation understands that it is common practice not to simulate crashes because of the adverse performance (psychological) effects this might have on cockpit crew. Indonesia AirAsia said on Tuesday it has upgraded pilot training and enhanced safety standards following the crash.
The report said the RTL had suffered 23 problems in the past twelve months, citing maintenance records, including four times during its fatal final journey. "The investigation found some inadequacy in the maintenance system, leading to the unresolved, repeated problem" with the rudder system, said Utomo, adding the fault in the RTL could have been due to extreme temperature changes that induced a crack in the electrical circuit board of the device. Interestingly, the NTSC report fell short of identifying the MRO responsible for the jet’s upkeep, and/or why the RTL had not been replaced.
Bad weather, as initially suspected, was ruled out as the cause of the disaster.
Interestingly, the Indonesian’s final report failed to include harder-hitting statements and findings proposed by the French air-crash investigation agency, known as BEA, which participated in the probe, reported The Wall Street Journal today. The tougher language rejected by the Indonesian authorities would have more explicitly identified pilot error and highlighted systemic maintenance lapses in the December accident, according to an appendix in the report.
More specifically,, the BEA investigators wanted to include, among other points, language indicating the cockpit crew’s “mishandling” and “inadequate actions” had resulted in the deadly stall. As well, BEA had requested that the words “inadequate maintenance actions” and a paragraph on government oversight of the carrier be part of the final report. The NTSC rejected both recommendations.
