Incident Overview
On 25 June 2018, at about 1141 local time, a Dassault Falcon 7X aircraft, registration VQ-BLP, was preparing for departure from Changi Airport in Singapore to Seychelles. The flight crew received a "BACKUP PUMP HI TEMP" caution message from the Crew Alerting System (CAS), indicating an overheat of the backup hydraulic pump. Shortly after, a cabin crew reported a burning smell in the cabin, and a "SMOKE: BAG COMP" warning message appeared.
Sequence of Events
The co-pilot inspected the aft baggage compartment but found no smoke or fire. Passengers were disembarked to the boarding room while the flight crew consulted with maintenance providers. Troubleshooting included multiple attempts to restart the backup hydraulic pump. During the third APU restart and pump activation, a small fire broke out in the mechanic service compartment at the tail of the aircraft, where the backup pump was located. The flight crew extinguished the fire using cockpit fire extinguishers. No persons were injured.
The aircraft had arrived at bay 304 at 0946 local time after a short flight from Seletar Airport. During the AT RAMP checklist, the flight crew was distracted by cabin and ground service crew requests and did not switch off the backup hydraulic pump. Consequently, the pump remained in AUTO mode for about 1 hour 50 minutes after engine shutdown, powering hydraulic system B via the APU.
Aircraft Information
The aircraft was a Dassault Falcon 7X, registered VQ-BLP, operated by PlanAir Enterprise Limited. It was powered by three Pratt & Whitney PW307A engines, with 2,622 hours and 717 cycles since new and no previous shop visits. The incident occurred at Bay 304, Changi Airport, Singapore.
Conclusion
The Transport Safety Investigation Bureau determined that the fire was caused by the operation of the backup hydraulic pump while its motor was dry due to a leak of hydraulic fluid. The interruption to the completion of the AT RAMP checklist resulted in the backup hydraulic pump being left in the AUTO mode for about 1 hour 50 minutes after engine shutdown, leading to overheating of the pump motor.