Synopsis
On 26 May 2013 at about 1342 hours, a Boeing 737-900 aircraft, registration PK-LHQ, operated by Lion Air, taxied to Bay C17 after landing at Changi Airport. The aircraft was scheduled to depart at 1450 hours. There was no aircraft parked on adjacent bays. After passengers had disembarked, at about 1405 hours, a wind of about 26 knots during a tropical rain caused the aircraft nose to swing to the right, pivoting about the right main landing gear. This resulted in damage to the aircraft, the passenger loading bridge (PLB) docked to the front left door, and a baggage loader.
Flight History
The aircraft was serviced by a team from the ground handling agent (GHA) of the operator. Wheel chocks were inserted when the aircraft stopped. The GHA team leader inserted the nose landing gear (NLG) steering bypass pin. The PLB was docked to Door 1L and remained docked after disembarkation. Two baggage loaders were parked on the right side: one at the front and one at the rear baggage compartment for loading. After arrival baggage was offloaded, the GHA commenced uploading 50 pieces of departure baggage into the rear compartment. The front compartment remained empty. Refueling was also conducted with the truck parked beside the No. 2 engine.
At 1400 hours, heavy rain began with winds up to about 26 knots. At about 1405 hours, the wind caused the aircraft nose to swing right, moving about 3.5 m from the apron centerline. The NLG rotated about 30 degrees to the right. The parking brakes were not set at the time.
Injuries
There was no injury in this incident.
Damage to Aircraft and Equipment
The swinging of the nose caused Door 1L to hit the PLB canopy, damaging a door hinge and preventing closure. The PLB sustained minor damage. The aircraft also hit the baggage loader at the front compartment; the loader went under the fuselage, causing a 90-cm scratch and dent at the bottom. The baggage loader sustained minor damage.
Meteorological Information
At the time of the incident, a wind sensor about 250 m from Bay C17 recorded 26.4 knots. The Meteorological Service Singapore (MSS) issued a thunderstorm warning at 1346 hours for 1400 to 1445 hours. At 1400 hours, a forecast indicated visibility 3 km, thunderstorm with moderate rain, and wind 10 knots gusting to 20 knots. Routine weather warnings were available on an MSS website, but the aerodrome operator, aircraft operator, and GHA did not subscribe to that service or use other wind information sources.
Additional Information
Refueling: At the time, both wing tanks were full (3,915 kg each) and the centre tank contained about 3,000 kg of fuel.
Baggage loading procedures: The aircraft manufacturer recommended loading the front baggage compartment first for a forward centre of gravity to increase wind resistance. The operator also required front-first loading, but there was no evidence this procedure was conveyed to the GHA. The loading instruction report did not specify loading sequence, and the load control officer did not emphasize front-first loading.
Wheel chocks: The GHA placed four chocks: one each at front and back of NLG, and one at the back of each MLG. The aircraft manufacturer's minimum configuration required four chocks (one forward and aft of one tyre per MLG). The operator required six chocks (front and back of each landing gear) apparently not conveyed. Furthermore, the operator had issued a Quality Assurance Notice on 21 March 2013 requiring eight chocks for transit aircraft in winds less than 35 knots, but this was also not conveyed.
Discussion
The investigation found that the rear baggage compartment was loaded first instead of the front, contrary to recommendations. The aircraft's weight distribution at the time gave an estimated wind speed limit of 20 to 25 knots, and the recorded wind of 26.4 knots exceeded that. The aircraft was vulnerable to being moved by wind. Contributing factors included the baggage loading sequence, wheel chock positioning, and the early insertion of the NLG steering bypass pin.