Investigation Summary
The flight was operating a multi-leg route from Severomuysk to Ulan-Ude. When the scheduled stop at Nizhneangarsk was cancelled due to weather, the crew diverted toward Ust-Barguzin. During the transit, the aircraft's ARP-6 automatic radio direction finder provided unstable readings, a condition the crew was warned about by the Ust-Barguzin tower. This technical instability, combined with poor crew coordination and a failure to report their actual position to the correct controller, led the aircraft to drift 32 kilometers to the right of its intended track. Despite being in thick cloud cover and rain, the crew claimed they had visual contact with the airfield to receive landing clearance. They subsequently mistook the dark mass of the Holy Nose Peninsula for the airfield environment and descended directly into the terrain. The investigation noted that the crew had improperly contacted the Ulan-Ude tower instead of Ust-Barguzin during the final approach phase.
Final Conclusions
The investigation concluded the primary cause was Controlled Flight Into Terrain (CFIT) resulting from pilot error and passive piloting. Contributing factors included the crew's intentional misinformation regarding visual contact with the airfield, the failure to follow established air rules regarding position reporting, and the use of unstable navigation equipment (ARP-6) which led to a significant course deviation.
Photographic Evidence (1)
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Systems & Failure Modes
ARP-6
An automatic radio direction finder found to be unstable, contributing to the 32km course deviation.
ARC-5
A radio compass that was destroyed in the crash, preventing investigators from determining its operational efficiency.
Interesting Facts
- 01The aircraft was 186 kg overweight at the time of takeoff.
- 02The crew intentionally misinformed the controller that they had the airfield in sight.
- 03The ARP-6 data finder was known to be unstable prior to the crash.
- 04Visibility at the crash site was approximately 5 kilometres with fog, rain, and low clouds.
- 05The impact occurred at a 10-degree left bank and a 2 to 3 degree descent angle.
Safety Actions & Advisories
Position Reporting Compliance
The investigation emphasized the necessity of following established air rules regarding position reporting and maintaining communication with the correct jurisdictional air traffic control tower, following the crew's failure to report to Ust-Barguzin.
Navigation Equipment Reliability
The accident highlighted the dangers of relying on unstable navigation equipment like the ARP-6 automatic radio direction finder in mountainous terrain and poor visibility.