Monday, September 1, 2008


Relevant Facts leading to the accident
On 01 Jan 2007, a B737-400 of Adam Air with 102 occupants on board went missing while on a domestic flight from Surubaya to Manado (Indonesia). Last contact with the aircraft was at 14:07, with the flight at FL350. Reports indicate that the flight changed course twice as a result of severe (70 kts) cross wind. The aircraft crashed into the sea killing all occupants. The FDR and CVR were finally recovered from the sea on 27/ 28 Aug, 2007.

Analysis revealed that the autopilot was engaged and was holding 5 deg. left aileron wheel to maintain wings level. Inertial Reference System (IRS) had malfunctioned. Both pilots had become engrossed with trouble shooting the IRS for at least the last 13 minutes of the flight, with minimal regard to other flight requirements. The pilots could not trouble shoot the problem and finally selected the IRS to Attitude. This action disengaged the autopilot, as per design. The auto pilot disengage warning was silenced after 4 seconds but it appears that no pilot was flying the aircraft. After the autopilot disengaged, the control wheel centred and the aircraft began a slow roll to the right. The aural alert, Bank Angle, sounded as the aircraft exceeded 35 deg. bank. The roll rate was momentarily arrested several times, but there was only one significant attempt to arrest the roll. Positive and sustained roll attitude recovery was not achieved. Even after the aircraft had reached a bank angle of 100 deg, with the pitch attitude approaching 60 deg nose down, the pilot did not roll the aircraft to wings level before attempting pitch recovery. The pilots appeared to have become spatially disoriented. Control was thereafter lost; the aircraft had a significant structural failure, and crashed into the sea. The aircraft had recorded a max of 3.5g/ 0.926M/ 490 kts.

Causes as per the Investigation

1. Flight crew co-ordination was less than effective. The PIC, who was also the PF for this segment, did not manage the task sharing; crew resource management practices were not followed.
2. The crew focused their attention on trouble shooting the IRS failure with neither pilot flying the aircraft.
3. After the autopilot disengaged and the aircraft exceeded 30 deg. right bank, the pilots appeared to have become spatially disoriented.
4. The company’s syllabus did not cover complete or partial IRS failure.
5. The pilots had not received training in aircraft upset recovery, including spatial disorientation.

Other Causal Factors

1. 154 recurring defects directly or indirectly related to the IRS between Oct and Dec 2006.
2. Poor Maintenance engineering supervision and oversight.

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