Investigation Summary
The aircraft was operating a multi leg transport mission from Yangon to Dawei, Myeik, and Bokpyin, and was on the return leg to Yangon. While cruising at 18,000 feet (FL180), the aircraft entered an area of cumulonimbus clouds. Investigation of the flight data recorders revealed that the crew had activated the wing anti icing system, but an alarm later triggered indicating icing in the engine air inlets. Simultaneously, the aircraft encountered a sudden increase in crosswinds, which jumped from 8 knots to 42 knots. This combination of aerodynamic degradation from icing and severe weather induced turbulence caused the aircraft to stall. The Y8 entered a spin from which the pilots were unable to recover before impacting the Andaman Sea.
Final Conclusions
The investigation concluded that the accident was caused by adverse weather conditions. Specifically, the aircraft experienced severe icing that affected its aerodynamic performance, followed by sudden wind shear. These factors led to a loss of control and a stall. The crew's inability to recover from the resulting spin led to the high-speed impact with the sea.
Video Analysis
No video analysis linked for this case file yet.
Systems & Failure Modes
Wing Anti-Icing System
A system used to prevent ice buildup on the leading edges of the wings; it was activated by the crew prior to the stall.
Engine Air Inlet Anti-Icing
A system designed to prevent ice from forming in the engine intakes; an alarm indicated this system was being overwhelmed or had failed to prevent icing.
Flight Data Recorder (FDR)
The 'black box' that provided investigators with critical data regarding the wind shear and icing alarms.
Interesting Facts
- 01The aircraft was nearly new, having been delivered to the Myanmar Air Force in March 2016.
- 02The total airframe time at the time of the accident was only 809 hours.
- 03The passengers included 35 military personnel and 73 family members, including 15 children.
- 04The Shaanxi Y8 is a Chinese produced version of the Soviet Antonov An 12.
- 05Search teams recovered the aircraft's tail section and flight recorders from the seabed on June 15 and 18, 2017.
Safety Actions & Advisories
Weather Avoidance Training
Following the investigation, emphasis was placed on improved pilot training regarding the avoidance of severe cumulonimbus formations and recovery techniques for high-altitude stalls in icing conditions.