Sriwijaya Air Flight SJ182 – January 9, 2021

On January 9, 2021, Sriwijaya Air Flight SJ182, a Boeing 737-500, crashed into the Java Sea just minutes after departing from Jakarta’s Soekarno-Hatta International Airport. All 62 people on board, including seven children and three infants, perished in the crash. Initial investigations revealed that the aircraft experienced problems with its autothrottle system in the days leading up to the accident, which may have contributed to the loss of control during flight.

Sequence of Events

Flight SJ182 was scheduled to fly from Jakarta to Pontianak in Indonesia, a routine domestic route. The Boeing 737-500, a 26-year-old aircraft, departed from Jakarta at 2:36 p.m. local time. Shortly after takeoff, the aircraft began to experience significant altitude fluctuations, climbing and descending irregularly. Approximately four minutes into the flight, the aircraft lost contact with air traffic control as it reached around 10,900 feet. The plane plunged into the Java Sea at high speed, disintegrating upon impact.

Rescue and recovery efforts began immediately, with teams scouring the area for debris and remains. The wreckage was spread across a wide section of the sea, indicating a high-impact crash. Within days, parts of the fuselage, personal items, and human remains were recovered, along with the aircraft’s flight data recorder (FDR) and cockpit voice recorder (CVR), which provided crucial information for the investigation.

Investigation and Technical Findings

The investigation was led by Indonesia’s National Transportation Safety Committee (NTSC), with assistance from international aviation safety agencies. Early reports indicated that the aircraft’s autothrottle system, which manages the engine thrust automatically, had malfunctioned several days prior to the accident and had not been fully addressed before the flight. The autothrottle is a critical component in maintaining the correct power settings for a safe climb and cruise, and its failure may have caused an asymmetric thrust situation, where one engine produced more power than the other.

The flight data recorder revealed that the autothrottle on the left engine reduced power shortly after takeoff, while the right engine continued at full thrust. This imbalance in engine power led to a significant roll, making the aircraft increasingly difficult to control. The pilots attempted to manually correct the imbalance but were unable to regain stable flight, leading to the rapid descent into the sea.

Human Factors and Flight Crew Response

While the mechanical issues with the autothrottle were a central factor, the investigation also examined the flight crew’s response to the situation. The pilots of Flight SJ182 were experienced, but the malfunction may have occurred rapidly and unexpectedly, leaving little time to react appropriately. The inability to manually override the autothrottle failure and effectively manage the asymmetric thrust contributed to the loss of control.

Additionally, questions were raised about whether the airline’s maintenance procedures were sufficient, especially considering the previous autothrottle issues reported days before the crash. The accident highlighted potential gaps in Sriwijaya Air’s maintenance oversight and the need for enhanced pilot training to manage complex in-flight emergencies.

Autothrottle Malfunctions: A Broader Context

Autothrottle systems are designed to reduce pilot workload by automatically adjusting engine power to maintain desired airspeeds and performance parameters. However, malfunctions in these systems can have serious consequences, particularly if pilots are not trained to handle such failures effectively. The asymmetric thrust condition caused by the autothrottle issue in this case is especially dangerous because it can lead to uncontrollable rolls and instability if not corrected immediately.

The aviation industry has seen similar incidents where autothrottle malfunctions have contributed to accidents, underscoring the importance of timely maintenance and pilot proficiency in handling non-standard situations.

Recommendations and Safety Measures

In the aftermath of the crash, the NTSC and international aviation safety organizations recommended several improvements in airline operations and safety protocols:

1. Enhanced Maintenance Oversight: Airlines must ensure that all mechanical issues, especially those involving critical flight systems such as autothrottles, are resolved before an aircraft is cleared for flight. Maintenance logs should be thoroughly reviewed, and no system malfunctions should be left unaddressed.

2. Pilot Training: Flight crews should receive comprehensive training in handling autothrottle malfunctions and other non-standard situations that could result in asymmetric thrust or loss of control. Simulator training that replicates such scenarios would be beneficial for preparing pilots to respond effectively in real-world emergencies.

3. Improved Communication of Known Issues: When mechanical issues arise, clear communication between maintenance crews and flight crews is essential to ensure that all known problems are fully understood and accounted for. Any unresolved issues must be communicated to the pilots so they are aware of potential risks.

4. Upgraded Systems and Technology: As part of the investigation’s long-term recommendations, there were calls for system upgrades on older aircraft models, including improvements to autothrottle systems and redundancy mechanisms that could help pilots regain control in the event of a failure.

Conclusion

The tragic loss of Sriwijaya Air Flight SJ182 serves as a stark reminder of the critical importance of aircraft maintenance, pilot training, and effective crisis management in aviation safety. The combination of technical malfunctions and human factors can have devastating consequences, as demonstrated by this accident. Moving forward, the aviation industry must continue to implement rigorous safety measures to prevent similar incidents, ensuring that all aircraft systems are fully operational and that flight crews are prepared to handle emergencies with precision.

The incident also reinforces the need for ongoing evaluation of aging aircraft and their systems. As the global fleet continues to age, airlines and regulatory bodies must be vigilant in maintaining and upgrading older aircraft to meet modern safety standards. The lessons learned from Flight SJ182 will undoubtedly contribute to future improvements in aviation safety, helping to prevent such tragedies from occurring again.