Crash Cause Determined For AirAsia Flight QZ8501

Indonesia has released the findings of the investigation into AirAsia Flight 8501 (QZ8501) that crashed on December 28 of last year, with all 162 people on board losing their lives. In the report, published following a 12-month investigation, the National Safety Transportation Board (KNKT) determine that the crash of the Airbus A320 passenger jet was due to a combination of computer and human errors.

Initial speculation that poor weather conditions and large thunderclouds played a role in the crash have now been officially ruled out. What caused the plane to crash was the technical malfunction of a faulty rudder control system and the inappropriate response of the crew. The report stated that the soldering on the rudder movement system had cracked repeatedly, causing the Rudder Travel Limiter Unit (RTLU) to malfunction 23 times during the previous year and four times during the flight itself, with increasingly frequent intervals three months before the flight that led to the crash. Pilots tried to fix the problem, but the autopilot switched off and the plane lost control, crashing into the Java Sea.

Indonesian Navy personnel show recovered parts of the aircraft AirAsia QZ8501.
SURABAYA, INDONESIA - JANUARY 07: Indonesian Navy personnel show recovered parts of the aircraft AirAsia QZ8501 during a handover ceremony from Indonesian Navy to NTSC to continue investigation on January 7, 2015 in Surabaya, Indonesia. A massive recovery operation is underway in waters off Borneo to recover bodies and debris from the missing AirAsia plane. AirAsia announced that flight QZ8501 from Surabaya to Singapore, with 162 people on board, lost contact with air traffic control at 07:24 a.m. local time on December 28. (Photo by Robertus Pudyanto/Getty Images)

A search operation revealed debris and the remains of some of the passengers from the flight off the coast of Borneo. The operation eventually managed to lift the tail section of the plane out of ocean. The bodies were identified and sent back to their families. Only 70 of the 162 on board were eventually recovered.

The Jakarta Post reported that while the flight crew did respond properly to the first three caution alerts from the system, it did not follow procedure on the fourth.

“[KNKT investigator] Nurcahyo added that RTLU failure was not a significant or fatal problem if the standard ECAM procedures were followed.

“The Flight Data Recorder (FDR) indicated that the pilot had followed ECAM procedures after the first three failures of the RTLU. The FDR also suggested that the Circuit Break (CB) could have been pulled, however, there was no concrete evidence, such as a video recording, to prove this Nurcahyo added.

“Investigators said that the CB was reset during each time the Flight Augmentation Computer (FAC) failed.

“During the intermittent FAC failures, the FAC 1 went offline followed by FAC 2. The pilot repetitively reset FAC 1 and 2. Electrical interference on FAC 1 and 2 occurred during the fourth caution signal, which in turn deactivated both the auto-pilot and auto-thrust. Kinetic energy turned into potential energy and caused the airplane to roll.”

This was the point of no return; conditions were such that pilots and crew had no chance of returning the plane to normal operation conditions, and the plane entered a 104-degree roll.

“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,” the report said.

The remains of Grayson Herbert Linaksita, a victim of the AirAsia flight QZ8501 disaster.
SURABAYA, INDONESIA - JANUARY 06: The remains of Grayson Herbert Linaksita, a victim of the AirAsia flight QZ8501 disaster, are layed out at Adi Yasa funeral house on January 6, 2015 in Surabaya, Indonesia. A massive recovery operation is underway in waters off Borneo to recover bodies and debris from the missing AirAsia plane. AirAsia announced that flight QZ8501 from Surabaya to Singapore, with 162 people on board, lost contact with air traffic control at 07:24 a.m. local time on December 28. (Photo by Robertus Pudyanto/Getty Images)

The investigation, a joint effort between French, Australian, Singaporean, and Malaysian authorities, therefore concluded that a series of technical errors caused by the cracked solder joint and the response of the flight crew doomed the flight. The crash of Flight QZ8501 was part of a series of Asian airline disasters in 2014, including the mysterious crash of Malaysian Airlines MH370.

CNN also reported that weaknesses in the training of AirAsia pilots also played a role in the crash, due to the lack of training in dealing with upsets, or when a plane’s angle is greater than 45 degrees.

“Our recommendation to AirAsia is to train their pilots flying the Airbus plane on how to make an upset recovery,” investigator Nurcahyo Utomo said.

Flight QZ8501 from Surabaya, Indonesia, was due to arrive in Singapore at 8:30 a.m., but disappeared from the radar at 6:17 a.m. The crash was the first ever for AirAsia Group, Asia’s famous low-cost airline. No distress signal was ever received from the flight.

(Photo by Robertus Pudyanto/Getty Images)