Incident Overview
On 11 November 2008, a Bombardier CL600 2B19 aircraft, registered as OE-LCF and operated by Tyrolean Airways Austria, was transiting Hungarian airspace when the crew received a fire indication for the right engine (engine #2). At 15:24 UTC, approximately 50 nautical miles east of Budapest Liszt Ferenc International Airport (LHBP), the crew shut down the affected engine and declared an emergency, requesting priority landing. The aircraft touched down safely at 15:38 UTC.
Initial Response and Findings
Following the landing, airport emergency services were activated. However, preliminary inspections revealed no signs of fire or damage on the engine. Technicians dispatched from the operator's base in Vienna conducted troubleshooting and identified that the false alarm was caused by attrition at loop B of the fire sensor transmitter, located near the 10th stage bleed air duct. Both fire bottles and their cartridges were replaced as a precaution. With loop B inoperative, the aircraft was dispatched under a Minimum Equipment List (MEL) provision (paragraph 26-11-01) for a single ferry flight to Vienna.
Subsequent Repairs
The Austrian Accident Investigation Board (BMVIT) provided details of the repairs performed at Vienna on 12 November 2008. The following actions were taken:
- Removal of the right engine cowlings and the 10th stage bleed air duct per AMM 71-12-01 and 36-11-31.
- Replacement of the right engine fire detection circuit card (zone A) and sensing elements 2A1EZ/2A3EZ.
- Installation of a new right engine 10th stage bleed duct.
- A satisfactory engine run per AMM 71-00-00.
- Re-inspection of the bleed duct clamp area and ducts for leaks, with no findings.
- Additional wiring checks and operational tests of the DCUs (Data Concentrator Units), all satisfactory.
- The aircraft was released to service.
Investigation Conclusion
The Transportation Safety Bureau (TSB) of Hungary, which initially opened the case, determined that no further technical investigation or action was required. The incident was closed without any safety recommendations, as no circumstances were revealed that would warrant them.
Probable Cause
The false fire alarm was caused by attrition at loop B of the fire sensor transmitter.