What happened
During a night flight into a high-altitude airport situated within a national park, an aircraft was performing a full instrument landing system (ILS) approach to runway 18. The airport, located at an elevation of 6,445 feet in a mountainous region, was operating without a control tower at the time of the incident. Because the tower was closed, the standard procedure for activating runway lighting required the pilot to key the microphone repeatedly on the Common Traffic Advisory Frequency (CTAF).
During the approach, the co-pilot attempted to activate the lights using the UNICOM frequency. This frequency had served as the CTAF until approximately six months prior to the accident. As the captain continued the approach below the established minimums without the runway lights being illuminated, the aircraft entered the landing flare phase. At this point, the captain reported that heavy snow and strong crosswinds had produced a white-out condition.
As a result of the visibility issues, the plane touched down on snow-covered ground located 195 feet to the left of the runway centerline, positioned between the runway and a taxiway. All four occupants managed to exit the aircraft without any injuries.
Findings
Investigation of the cockpit revealed two different ILS Runway 18 approach plates. One plate was outdated and incorrectly listed the UNICOM frequency as the CTAF. The second plate was current and correctly identified the tower frequency as the proper CTAF. The use of an incorrect radio frequency for lighting activation prevented the crew from illuminating the runway.