What happened
While conducting an instrument landing system (ILS) approach to Runway 27 at Victoria International Airport, the crew of a Bombardier CL-600-2B16, registration C-FSJR, experienced an unexpected flight path deviation. The aircraft was approximately 10 nautical miles from the airport and 5 nautical miles north of the localizer course, descending through 4,000 feet, when the pilot engaged the autopilot in approach mode.
Upon activation, the aircraft turned to the right, and the navigation systems indicated that the localizer had been captured. However, the crew realized the autopilot had intercepted an incorrect course, as the actual localizer was located roughly 5 nautical miles to their south. As the aircraft descended through a scattered cloud layer, the crew visually confirmed they were being directed toward Mount Tuam on Saltspring Island. The crew responded by switching the autopilot to heading mode to re-establish the correct intercept, eventually landing the aircraft safely with no injuries or damages.
The investigation
The investigation focused on the mechanics of the localizer capture and the adherence to established flight procedures. Investigators examined the compatibility between ground-based ILS installations and airborne automated flight control systems (AFCS). It was determined that the aircraft was positioned at an azimuth of approximately 26 degrees from the localizer course at the time of the event.
While the aircraft was within the recommended distance from the airfield, it was positioned near or beyond the limits where ILS integrity is verified. The investigation also reviewed the procedural defenses outlined in the Aeronautical Information Publication (AIP), which suggest that approach mode should not be selected until the aircraft is within 18 nautical miles of the threshold and within 8 degrees of the inbound course. The investigation noted that this event was one of several recent recurrences of such captures.
Findings
- Incompatibility between certain ground and airborne ILS equipment can cause false or incorrect localizer course captures.
- The crew selected approach mode while the aircraft was near or beyond the limits at which the integrity of the ILS is verified.
- Established procedural defenses in the AIP, if followed, can reduce the risk of such captures.
- Recent recurrences of this phenomenon may necessitate a reminder to pilots regarding the guidance provided in the AIP, particularly for foreign carriers.