Investigation Summary
The flight was operating in an area with active thunderclouds and moderate rain. While maintaining a steady cruise at 350 km/h, the aircraft's flight dynamics were suddenly disrupted by a massive rudder deflection. The investigation noted that the rudder initially moved 25 degrees, followed by a secondary 9-degree deflection. This induced a severe yaw and roll that the pilots could not fully counteract. As the crew struggled for control, the elevators also deviated, causing the nose to pitch up by 30 degrees. This maneuver led to a stall and a subsequent tailspin. During the descent, the propellers were found to have been feathered, though it is unclear if this was a result of crew action or system failure during the loss of control. The aircraft struck the ground approximately 14.5 kilometers southeast of Chernihiv Airport with a vertical descent rate of nearly 100 m/s.
Final Conclusions
The official inquiry concluded the crash was caused by a loss of control following a rudder deflection that occurred immediately after the autopilot was disconnected. However, the root cause of the deflection remains undetermined. Investigators proposed several possibilities, including a mechanical failure of the rudder trimming device, an electrical fault in the control systems, or an accidental activation of the rudder trim switch by the flight crew. No definitive evidence was found to isolate one cause over the others.
Photographic Evidence (1)
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Systems & Failure Modes
Rudder Trim Control
A switch-operated system that adjusts the neutral position of the rudder; suspected of accidental activation or electrical failure.
Autopilot
The flight control system was disconnected just as the rudder hardover began, though the sequence of causality is unclear.
Propeller Feathering System
The propellers were found in the feathered position at the time of the spin, which significantly reduced thrust and control surface effectiveness.
Interesting Facts
- 01The aircraft was relatively new, having been manufactured only 14 months prior to the accident.
- 02Weather at the time included cumulonimbus clouds, moderate rain, and 6 m/s winds.
- 03The rudder deflection occurred almost simultaneously with the disconnection of the autopilot.
- 04The impact occurred on a bearing of 245 degrees from the Chernihiv airport.
Safety Actions & Advisories
Rudder Trim Switch Modification
Following the investigation into the unexplained rudder deflection, recommendations were made to modify the rudder trim control switch on An-24 aircraft to include a protective guard or recessed design to prevent accidental activation by the crew.