Piper PA-28-140 N6323R accident near Rush Valley, Utah

Probable cause

The pilot’s misidentification of a mountain pass at night, which resulted in controlled flight into terrain. Contributing to the accident were the pilot’s overconfidence based on her previous aviation experience and fatigue due to both the time of the flight and her work schedule. Also contributing was the pilot’s decision not to install an automatic dependent surveillance-broadcast (ADS-B) system, which forced a flightpath close to mountainous terrain to avoid the Mode-C and ADS-B Out veil.

NTSB analysis

The accident flight was the second leg of an overnight, multi-leg cross-country from the pilot’s home airport in Northern Montana to her grandfather’s house in Southern California. The pilot was traveling with her granddaughter, and the trip was planned as a Father’s Day surprise. The pilot opted to fly overnight to avoid the heat and turbulence associated with flying over the desert during the day.

The airplane was not equipped with an ADS-B transponder. In order to avoid both the Salt Lake City International Airport (SLC) Mode-C and automatic dependent surveillance -broadcast (ADS-B) system out veil an adjacent military operation area (MOA), the pilot chose to fly through a narrow, mountainous corridor. Due to the altitude limitation of the MOA, the pilot could not fly over the mountain range.

Radar data confirmed that the airplane passed very close to terrain as it avoided the SLC Mode C veil, and ultimately turned into a valley and rising terrain just short of a mountain pass that led away from the airspace and in the direction of the destination. Although the moon was in a position where it would have silhouetted the mountains, it was only 50 percent illuminated, and a broken cloud layer was present that would have obscured most of the available moonlight.

The pilot had already worked a full day and departed on the flight late in the afternoon. The accident occurred at about the halfway point of the trip, about 7 hours after departure from her home airport, almost 18 hours from when she likely woke to report for work, and about the time she would normally have gone to sleep. Therefore, she was likely suffering the effects of fatigue as a result of the flight time and extended time awake. Additionally, her circadian systems were not actively promoting alertness because she was operating the airplane at a time she would normally have been asleep.

The majority of the pilot’s flight experience was as an Army helicopter pilot, with about ¼ of her flight time accrued at night, often over desert terrain, frequently with night vision goggles. Since then, she had taken a long break from flying, and recently purchased the accident airplane and attained her fixed wing private pilot’s license. The accident flight was the longest flight she had flown since leaving the Army, and her longest flight single-pilot in a fixed-wing airplane. The pilot’s decision making associated with the timing of the flight over mountainous terrain suggests overconfidence based on her previous flight experience.

The pilot was carrying oxygen to aid with her night vision; although she had taken a borrowed GPS moving map system that was capable of displaying terrain features, this was the first time she had used it, and she was likely not proficient in its operation.

The airplane crossed into the Mode-C and ADS-B Out veil twice as it followed a meandering track around the SLC airspace and came perilously close to terrain on two occasions, further indicating that the pilot was possibly suffering the effects of fatigue and either not proficient in the operation of the GPS unit or not using it. It is likely that the pilot lost situational awareness and turned prematurely into the valley, possibly mistaking it for the pass, resulting in controlled flight into terrain.

Text from the NTSB. Open the NTSB docket for WPR21FA231 for the full record.