Investigation Summary
The aircraft was undergoing a ferry and test flight from the Lukhovitsy Aviation Plant to Vnukovo International Airport after maintenance. The final investigation revealed that during maintenance, two of the four angle of attack (AoA) sensors were incorrectly installed, with their positions swapped or misaligned by approximately 5 degrees. Shortly after takeoff, the flight control system received conflicting data: while the aircraft was at a stable pitch, the erroneous sensor data triggered the automated flight protection systems. This caused the aircraft to enter a series of nose-down commands that the crew, believing they were facing a stall, struggled to counteract. The crew consisted of two test pilots and a flight technician from the Sukhoi design bureau. The Russian Ministry of Transport noted that the flight was conducted under a ferry permit that may not have fully accounted for the maintenance status of the airframe.
Final Conclusions
The Interstate Aviation Committee (MAK) concluded that the accident was caused by the incorrect installation of two angle of attack (AoA) sensors during maintenance at the Lukhovitsy Aviation Plant. The sensors were swapped, leading to a 5-degree bias in the data provided to the flight control system. This error triggered the automated stall protection system (Alpha Floor) shortly after takeoff, which commanded a continuous nose-down pitch. The crew, unable to diagnose the sensor mismatch in the limited time available, was unable to override the automated commands before the aircraft impacted the ground.
Photographic Evidence (1)
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Systems & Failure Modes
Angle of Attack (AoA) Sensors
Vanes that measure the angle between the wing and the oncoming airflow; faulty data from these sensors can trigger automated stall protection.
Air Data Computer (ADC)
Processes inputs from pitot tubes and static ports to provide airspeed, altitude, and angle of attack information to the cockpit and flight controls.
Interesting Facts
- 01The flight was a ferry mission following maintenance at the Lukhovitsy Aviation Plant.
- 02All three occupants were employees of Sukhoi, including two pilots and a flight technician.
- 03The aircraft involved was manufactured in 2014 and had the serial number 95078.
- 04The crash occurred approximately 80 kilometers southeast of its destination, Vnukovo International Airport.
- 05The Russian Ministry of Transport claimed the aircraft did not have the required permission to fly at the time of the accident.
Safety Actions & Advisories
Maintenance Procedure Review
The Interstate Aviation Committee and Russian aviation authorities initiated a review of sensor installation procedures for the Sukhoi Superjet 100 fleet following the preliminary findings.
Known Controversies & Unanswered Questions
Flight Authorization Dispute
Reference ↗The Russian Ministry of Transport stated the aircraft did not have permission to fly, while the flight was being conducted as a post-maintenance test/ferry flight by Sukhoi employees.