Incident Overview
On 28 January 2019 at approximately 0815 hours Singapore time, an Airbus A350-900 aircraft (registration 9V-SMS) parked at Singapore Changi Airport was involved in an incident with a catering truck. The truck was servicing Door 4R, the aft-most door on the right side, during food cart unloading and replenishment. The incident resulted in damage to the door hinge and frame.
Sequence of Events
The catering truck operator raised the cabin platform to nearly level with the aircraft floor deck. While conducting food cart operations, the operator noticed the platform had lowered by itself, becoming unlevel with the deck. Attempting to raise the platform using the up-down toggle switch at the front cabin control panel, he found the switch inoperative. He then moved to the rear cabin control panel. From that position, he could not see the platform, so he asked a colleague to monitor the platform's rise relative to Door 4R. When the colleague signalled impending contact with a safety shoe placed under the door, the operator released the toggle switch, but the platform continued rising. He then activated the emergency stop switch, halting the platform, but it had already made contact, lifting Door 4R upward.
Damage
The upward lift twisted the door hinge and damaged the adjoining door frame. The safety shoe was found compressed between Door 4R and the platform.
Personnel Information
The truck operator, aged 57, held an Airport Driving Permit and had 17 years of experience operating catering trucks.
Catering Truck Systems
Cabin Control Panels
The truck had front and rear control panels, each with a master switch, an up-down toggle switch, and an emergency stop switch. The operator would depress the master switch and use the toggle to adjust platform height; releasing the master switch or activating the emergency stop would halt movement.
Safety Shoe System
A safety shoe was placed on the platform under the open aircraft door to prevent damage. If the aircraft door compressed the shoe, it was designed to trigger automatic lowering of the platform. In this incident, the safety shoe was compressed but did not trigger the auto-lowering feature.
Investigation Findings
Uncommanded Platform Lowering
CCTV footage showed the platform lowering without any down command. Tests with weight blocks revealed the platform lowered by about 6 cm every 20 minutes. The truck manufacturer noted the optimal engine idle speed was 900 RPM, but the incident truck had an idle speed of 1,200 RPM. After resetting to 900 RPM, the lowering rate decreased to about 1 cm every 45 minutes. No evidence of intentional modification was found.
Control Panel Function
Post-incident examination by an independent vehicle surveyor and the investigation team found both front and rear control panels to be working normally. The reported abnormalities could not be replicated.
The investigation did not identify a single root cause; the incident involved a combination of uncommanded platform drift and failure of the safety shoe system to activate.