What happened
On 6 September 2001, an Embraer EMB-145EP, registration G-RJXA, was operating a scheduled passenger flight from Glasgow to Manchester. The flight was proceeding normally under clear weather conditions until approximately 105 seconds after applying climb thrust. While climbing through 2,5 and 00 feet, the crew received a fire warning and a Master Warning indication for the number one engine.
At the time of the alert, the co-pilot was hand-flying the aircraft while the commander was communicating with Air Traffic Control. The crew immediately initiated emergency procedures, with the commander discharging the first fire extinguisher shot. The fire warning ceased shortly after the discharge. The crew declared a MAYDAY, requested radar vectors for a return to Glasgow, and prepared for a single-engine approach.
During the descent, the cabin crew relocated passengers to ensure clear access to over-wing exits. The aircraft completed an uneventful landing at Glasgow Airport. Following the landing, the fire service inspected the aircraft and confirmed there were no remaining signs of fire. There were no fatalities and no injuries to the 23 passengers or 4 crew members on board.
The investigation
The AAIB examined the engine compartment and found evidence of heat damage, including a scorched vent panel and melted turbine blades within the Air Turbine Starter (ATS) casing. The investigation focused on the pneumatic engine starting system, specifically the ATS mounted on the engine accessory gearbox.
Technical analysis of the ATS, conducted at the manufacturer's facility in the USA, revealed that the unit's overrun bearings had seized. This seizure was caused by excessive axial load on the shaft. The investigation also noted that the ATS on G-RJXA was an older version of the component, predating recent design modifications intended to correct shaft dimension errors.
Findings
- The engine fire was caused by the seizure of overrun bearings within the ATS clutch due to excessive axial load.
- This mechanical failure resulted in a high-speed "back drive" event, generating intense heat.
- The heat was sufficient to vaporize the ATS lubricating oil, which then ignited when the external casing reached a critical temperature.
- The specific ATS installed on the aircraft was an older standard that had been superseded in newer production aircraft to address shaft interference issues.
- The crew handled the emergency effectively, following all necessary checklists and procedures.