What happened
During a cruise climb through 15,000 feet MSL, the flight crew of a Bombardier CL-600-2B19 reported hearing a small thud. While the crew monitored the engines and noted no other anomalies, they initially attributed the sound to possible wake turbulence and continued to their destination. However, a post-flight inspection revealed that the left engine exhaust nozzle and fairing had departed the aircraft.
The missing left engine exhaust nozzle was located approximately 26.5 nm west-southwest of the departure airport.
The investigation
An examination of the recovered exhaust nozzle revealed that the attachment hardware was missing. Investigators found that the bolt holes used to secure the nozzle to the engine were elongated and showed evidence of fretting.
Records indicated that the manufacturer had issued Service Bulletin CF34-NAC-78-024 on January 24, 2003, specifically to address exhaust nozzle bolt attachment failures. This bulletin required replacing existing hardware with new, improved hardware within a maximum of 4,000 hours. At the time of this event, the aircraft had accumulated 3,440 hours since new, and maintenance records showed that the service bulletin had not been complied with.
Following the incident, the operator inspected their entire fleet of Bombardier CL-600-2B19 regional jets. The inspection identified three additional aircraft with either missing or loose exhaust nozzle attachment hardware.