What happened
On December 25, 2003, TransAsia Airways flight GE006, an ATR72-212A (registration B-22805), was operating a domestic flight from Hualien Airport to Sungshan International Airport in Taipei. The flight was carrying eighteen passengers and a total of four crew members.
During the final approach, the flight crew observed more than ten intermittent warning signals on the centralized crew alert system, including a brief red warning light. Following touchdown at Sungshan International Airport, the crew observed the number one engine fire warning light illuminate during the landing roll. In response, the pilots moved the number one engine fuel condition lever to the cut-off position and attempted to discharge the fire extinguishing bottle, though the bottle was not actually triggered. The aircraft subsequently taxied to the ramp.
An inspection of the number one engine following the event revealed a perforation on the top right side of the rear inlet case, accompanied by fire soot and damage to nearby electrical wiring. There were no injuries to the passengers or crew.
The investigation
The investigation, conducted by the Taiwan Transportation Safety Board (TTSB), involved international cooperation with the BEA (France), the TSB (Canada), and engine manufacturers Pratt & Whitney Canada and SECA. The investigation included a detailed teardown of the engine at SECA in Paris and an examination of the accessory gearbox at Pratt & Whitney Canada in Montreal.
Investigators analyzed flight data recorder (FDR) and cockpit voice recorder (CVR) data, which showed that oil pressure began dropping shortly before touchdown. The analysis focused on the condition of the engine's internal components, specifically the breather impeller and the accessory gearbox.
Findings
Technical analysis established that the breather impeller disintegrated due to extreme heat, which caused a rupture in the rear inlet case. This failure allowed hot oil and gases to escape, subsequently triggering the engine fire detection system. The investigation determined that temperatures within the engine rear inlet case had risen sufficiently to ignite the engine lubricating oil. While the exact heat source that initiated the initial oil ignition could not be definitively identified, the structural failure of the impeller was the primary driver of the fire warning.
Safety action
Following the investigation, a recommendation was made to Pratt & Whitney Canada to investigate the causes of high oil temperatures in this engine type and share findings with operators. In response, TransAsia Airways implemented enhanced monitoring of engine oil service, including more rigorous inspections during preflight, transit, and weekly checks, as well as improved procedures for reporting oil seepage.