What happened
On October 24, 2005, a Canadair CL-600-2B19, operating as D-ACJG, was conducting a scheduled IFR flight from Munich (EDDM) to Zurich (LSZH). While cruising approximately 20 nautical miles east of the TRA VOR/DME, the flight crew detected an unusual odor within the cockpit.
In response to the developing situation, the crew initiated an emergency diversion to Zurich. The aircraft landed safely at LSZH without further incident.
The investigation
The investigation focused on identifying the origin of the strange smell reported by the crew. Investigators determined that the odor was originating from a specific component within the aircraft's environmental control system. Specifically, a filter located in the left air-conditioning pack was identified as the source of the smell.
Findings
Technical analysis confirmed that the faulty air-conditioning filter was the sole cause of the odor. Because there was no visible smoke present during the flight and the risk of the situation escalating into a more dangerous event was ruled out, the event did not meet the criteria for a severe incident. The investigation also noted that the flight crew performed their duties correctly, following the appropriate checklists to manage the diversion.