Download This Article (PDF - 500 KB)
High-altitude ice crystals in convective weather are now recognized as a cause of engine damage and engine power loss that affects multiple models of commercial airplanes and engines. These events typically have occurred in conditions that appear benign to pilots, including an absence of airframe icing and only light turbulence. The engines in all events have recovered to normal thrust response quickly. Research is being conducted to further understand these events. Normal thunderstorm avoidance procedures may help pilots avoid regions of high ice crystal content.

by Jeanne Mason,
Senior Specialist Engineer,
Engine Performance and Operability,
Propulsion Systems Division

Since 1990, there have been at least 100 jet engine power-loss events on both commuter and large transport airplanes, mostly at altitudes higher than 22,000 feet, the highest altitude where airframe icing is expected to exist. "Power loss" is defined as engine instability such as a surge, stall, flame­out, or rollback that results in a sub-idle operating condition. High-altitude ice crystals are believed to have caused most or all of these events.

This article explains the ice crystal phenomenon, how ice crystals cause power loss, the types of power-loss events, where and when engine power-loss events have occurred, conditions associated with ice crystal formation, and recommendations for flight near convective weather. It also discusses the importance of pilot reporting of ice crystal power-loss events.

Download This Article (PDF - 500 KB)