What happened
On 26 May 2013, a Lion Air Boeing 737-900, registration PK-LHQ, was parked at Bay C17 of Changi Airport following a scheduled passenger flight. While the aircraft was undergoing ground servicing, including refueling and baggage unloading, a tropical thunderstorm moved over the aerodrome. At approximately 1405 hours, wind speeds reached roughly 26 knots.
The force of the wind caused the aircraft's nose to swing approximately 3.5 meters away from the apron centerline, pivoting around the right main landing gear. This movement caused the aircraft's front left door to strike the passenger loading bridge (PLB) canopy, damaging a door hinge and preventing the door from closing. Additionally, the aircraft's nose struck a baggage loader, resulting in a 90-cm dent and scratch on the lower fuselage. There were no injuries reported during the incident.
The investigation
The investigation examined the ground handling procedures, the aircraft's weight distribution, and the meteorological conditions at the time of the event. Investigators looked into the specific placement of wheel chocks, the sequence of baggage loading, and the status of the nose landing gear steering bypass pin. The inquiry also reviewed the communication between the airline operator, the ground handling agent (GHA), and the aerodrome operator regarding weather warnings and safety protocols.
Findings
Several contributing factors were identified that left the aircraft vulnerable to the wind:
- Improper baggage loading sequence: The rear baggage compartment was loaded before the front compartment. Following manufacturer recommendations to load the front compartment first would have created a more forward center of gravity, increasing the aircraft's resistance to pivoting.
- Inadequate wheel chock configuration: The GHA used a four-chock setup that differed from the manufacturer's recommendation. Furthermore, the operator's specific requirement to use eight chocks for transit aircraft was not communicated to the GHA.
- Early insertion of the steering bypass pin: The nose landing gear steering bypass pin had been inserted early. Had it remained out, the resistance of the wheels would have helped prevent the nose from rotating.
- Lack of weather monitoring: Neither the airline, the GHA, nor the aerodrome operator had active procedures to monitor or disseminate real-time wind speed warnings to ground crews.
Safety action
Following the investigation, the operator instructed the GHA to implement specific safety protocols, including using eight wheel chocks for winds below 35 knots, prioritizing the loading of the front baggage compartment, and delaying the insertion of the nose landing gear steering bypass pin until the tow bar is ready for connection.