Severe Icing Pilot Reports Across the United States: Relationships Among Icing Type, Terrain, Altitude, Aircraft, Region, and Climate

The bane of all pilots – severe icing! Clear, rime, and mixed severe icing can quickly become life-threatening in aviation. Even the most experienced pilots must avoid encountering these atmospheric conditions. This study analyzes the collection of severe icing pilot reports (PIREPs) across the United States from June 2001 to December 2010. Only “severe” reports are studied, i.e., not moderate to severe, not moderate, not light, etc. They are categorized in terms of icing type, flight altitude, aircraft type, time of year, ENSO phase, terrain, region, and so on.

It comes as no surprise that the majority of severe category pilot reports are “urgent” PIREPS. The most frequent severe icing PIREP months were, as expected, the winter months. Icing type was mostly rime, followed by mixed, and then clear. Next were the spring, fall and summer months, which are impacted by different phenomena such as thunderstorm activity. With this, severe icing altitudes, locations, and aircraft affected vary significantly among the different months of the year, and some interesting climate effects were observed during the study.

The number of severe icing PIREPS decreased by almost 90% over the decade. Possible reasons for this drop, and results of this continuing study regarding icing type, terrain, flight altitude, aircraft, region of the United States, climate, and other factors will be discussed.