Investigation Summary
Flight RNI463 was a scheduled regional service originally planned for a Khabarovsk–Nikolayevsk-on-Amur–Nelkan route. Due to snow removal at Nikolayevsk-on-Amur, the flight was rerouted to Khabarovsk–Chyumican–Nelkan, but the crew later elected to bypass Chyumican and fly directly to Nelkan. During the approach to runway 04, while at an indicated airspeed of 100 knots and a height of 150 meters, the right-hand propeller blades transitioned to a pitch of minus 1.8 degrees. This was significantly below the minimum inflight pitch limit of 13.5 degrees. The resulting asymmetric drag and thrust caused the aircraft to lose altitude rapidly. The investigation by the Interstate Aviation Committee (MAK) determined that the failure was caused by the simultaneous malfunction of the Beta Feedback system and the Pitch Lock system. Because this specific failure mode had been classified as extremely improbable during certification (1 in 10^-14), the Airplane Flight Manual (AFM) contained no emergency procedures for an inflight beta range transition, leaving the crew with no established recovery protocol. The aircraft crashed 1,200 meters from the runway threshold.
Final Conclusions
The Interstate Aviation Committee (MAK) released its final report in August 2019. The direct cause was the uncommanded inflight transition of the right-hand propeller blades to a negative angle due to failures in the Beta Feedback and Pitch Lock systems. The report noted that while the crew had deviated from the standard Pitch Lock Test procedure during pre-flight, this likely did not contribute to the accident as the specific components that failed would not have been detected by that test. The investigation resulted in 24 safety recommendations, including the creation of new emergency procedures for propeller malfunctions.
Video Analysis
The Miracle Survivor of Flight 463 — A detailed look at the mechanical failure of the Let L-410 propeller system that led to the 2017 crash in Nelkan and the survival of a 3-year-old girl.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
Igor Leonidovich Shumakov, age 42
First Officer
Alexander Alexandrovich Zuev, age 30
Systems & Failure Modes
BETA Feedback System
A system designed to provide feedback on propeller blade pitch; its failure allowed the blades to move into the restricted beta (ground) range while in flight.
Pitch Lock System
A safety mechanism intended to prevent the propeller blades from reaching dangerously low pitch angles in the event of a primary governor failure.
General Electric H80-200 Engines
The turboprop engines powering the Let L-410UVP-E20, which utilize a complex governor and feedback system to manage propeller pitch.
Interesting Facts
- 01The aircraft was relatively new, having first flown in 2015 with only 1,693 airframe hours.
- 02A three-year-old girl was the only survivor of the crash.
- 03The propeller pitch reached -1.8 degrees, while the minimum allowed inflight pitch was 13.5 degrees.
- 04The accident occurred in a mountainous, marshy area with snow depth between 50 and 100 cm.
Safety Actions & Advisories
Emergency Procedure Implementation
Following the accident, new instructions were issued to pilots requiring the affected propeller to be feathered immediately if it enters the beta range in flight.
MAK Safety Recommendations
The Interstate Aviation Committee issued 24 safety recommendations to address technical failures and improve crew training for propeller pitch malfunctions.
Location
ACCIDENT SITE · Coordinates taken from the official investigation report.