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B734, en-route, Sulawesi Indonesia, 2007

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Summary
On 1 January 2007, a B737-400 crashed into the sea off Sulawesi, Indonesia, after the crew lost control of the aircraft having become distracted by a minor technical problem.
Event Details
When January 2007
Actual or Potential
Event Type
Human Factors, Loss of Control
Day/Night Day
Flight Conditions IMC
Flight Details
Aircraft BOEING 737-400
Operator Adam Air
Domicile Indonesia
Type of Flight Public Transport (Passenger)
Origin Surabaya/Juanda International Airport
Intended Destination Manado/Sam Ratulang International Airport
Take off Commenced Yes
Flight Airborne Yes
Flight Completed No
Flight Phase Cruise
ENR
Location En-Route
Origin Surabaya/Juanda International Airport
Destination Manado/Sam Ratulang International Airport
Location
Approx. off Sulawesi coast, Indonesia
Loading map...


General
Tag(s) Inadequate Airworthiness Procedures,
Inadequate Aircraft Operator Procedures,
Ineffective Regulatory Oversight
HF
Tag(s) Distraction,
Inappropriate crew response - skills deficiency,
Inappropriate crew response (technical fault),
Ineffective Monitoring,
Manual Handling,
Procedural non compliance
LOC
Tag(s) AP Status Awareness,
Flight Management Error,
Flight Control Error"Flight Control Error" is not in the list (Airframe Structural Failure, Significant Systems or Systems Control Failure, Degraded flight instrument display, Uncommanded AP disconnect, AP Status Awareness, Non-normal FBW flight control status, Loss of Engine Power, Flight Management Error, Environmental Factors, Bird or Animal Strike, ...) of allowed values for the "LOC" property.,
Extreme Bank,
Extreme Pitch
Outcome
Damage or injury Yes
Aircraft damage Hull loss
Fatalities Most or all occupants (102)
Causal Factor Group(s)
Group(s) Aircraft Operation,
Aircraft Technical
Safety Recommendation(s)
Group(s) Aircraft Operation,
Aircraft Airworthiness,
Air Traffic Management
Investigation Type
Type Independent

Description

On 1 January 2007, a B737-400 being operated by Adam Air on a scheduled passenger flight crashed into the sea off Sulawesi, Indonesia, after the crew lost control of the aircraft having become distracted from managing the aircraft by becoming focussed exclusively on a minor technical problem and then failing to recover it to normal flight promptly before recovery became impossible.

Synopsis

The following is an extract from the Synopsis to the official accident report published by the Komite Nasional Keselamatan Transportasi (KNKT)/ National Transportation Safety Committee (NTSC):

” On 1 January 2007, a Boeing Company 737-4Q8 aircraft, registered PK-KKW, operated by …AdamAir…was on a scheduled passenger flight from Surabaya (SUB), East Java to Manado (MDC), Sulawesi, at FL 350 (35,000 feet) when it disappeared from radar… There were 102 people on board… the wreckage was located in the ocean at a depth of about 2,000 meters…

The CVR revealed that both pilots were concerned about navigation problems and subsequently became engrossed with trouble shooting Inertial Reference System (IRS) anomalies for at least the last 13 minutes of the flight, with minimal regard to other flight requirements. This included identification and attempts at corrective actions. The DFDR analysis showed that the aircraft was in cruise at FL 350 with the autopilot engaged. The autopilot was holding 5 degrees left aileron wheel in order to maintain wings level. Following the crew’s selection of the number-2 (right) IRS Mode Selector Unit to ATT (Attitude) mode, the autopilot disengaged. The control wheel (aileron) then centered and the aircraft began a slow roll to the right. The aural alert, BANK ANGLE, sounded as the aircraft passed 35 degrees right bank. The DFDR data showed that 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 degrees, with the pitch attitude approaching 60 degrees aircraft nose down, the pilot did not roll the aircraft’s wings level before attempting pitch recovery in accordance with standard operating procedures. The aircraft reached 3.5g, as the speed reached Mach 0.926 during sustained nose-up elevator control input while still in a right bank. The recorded airspeed exceeded Vdive (400 kcas), and reached a maxim um of approximately 490 kcas just prior to the end of recording.

A thump, thump sound was evident on the CVR about 20 seconds from the end of the recorded data. Flight recorder data indicated that a significant structural failure occurred when the aircraft was at a speed of Mach 0.926 and the flight load suddenly and rapidly reversed from 3.5g to negative 2.8 g. This g force and airspeed are beyond the design limitations of the aircraft. At the time of the thump, thump sound, the aircraft was in a critically uncontrollable state. The PIC did not manage task sharing and crew resource management practices were not followed. There was no evidence that the pilots were appropriately controlling the aircraft, even after the BANK ANGLE alert sounded as the aircraft’s roll exceeded 35 degrees right bank.

This accident resulted from a combination of factors, including the failure of the pilots to adequately monitor the flight instruments, particularly during the final 2 minutes of the flight. Preoccupation with a malfunction of the Inertial Reference System (IRS) diverted both pilots’ attention from the flight instruments and allowed the increasing descent and bank angle to go unnoticed. The pilots did not detect and appropriately arrest the descent soon enough to prevent loss of control.

[Training Issues]

At the time of the accident, AdamAir did not provide their pilots with IRS malfunction corrective action training in the simulator, nor did they provide aircraft upset recovery training in accordance with the Airplane Upset Recovery Training Aid developed by Boeing and Airbus. In accordance with Civil Aviation Safety Regulations, Indonesian operators are required to provide training in emergency or abnormal situations or procedures. However, at the time of the accident, the Indonesian regulations did not specifically require upset recovery to be included in their flight operations training.

[Maintenance Issues]

Technical log (pilot reports) and maintenance records showed that between October and December 2006, there were 154 recurring defects, directly and indirectly related to the aircraft’s Inertial Reference System (IRS), mostly the left (number-1) system. There was no evidence that the airline’s management was aware of the seriousness of the unresolved and recurring defects. There was no evidence that AdamAir included component reliability in their Reliability Control Program (RCP) to ensure the effectiveness of the airworthiness of the aircraft components for the fleet at the time of the accident.”

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Further Reading

For further information, see the full KNKT Accident Report