Nov. 13, 2018

Operators are encouraged to review new weather information as the winter flying season approaches.

The FAA recently published Information for Operators (InFO) 18011 updating coding requirements for snow pellets and small hail in Meteorological Terminal Aviation Routine Weather Reports (METAR) or Aviation Special Weather Reports (SPECI) to assist pilots in interpreting holdover time limitations. View the FAA’s InFO.

Holdover time is the estimated period for which anti-icing or deicing fluid will prevent the accumulation of ice, snow or frost on an aircraft. The fluids are classified according to their composition, purpose and procedure for application.

Currently, snow pellets and small hail share a single code of “GS.” This requires the weather observer to augment the weather report to state specifically whether snow pellets or small hail are observed.

In a 2014 notice, the now-cancelled 8900.275, the FAA determined small hail to be meteorologically equivalent to moderate ice pellets for anti/de-icing purposes, making specification of precipitation type more critical for purposes of determining holdover time limitations.

Small hail will now be reported as “GR” and snow pellets as “GS.” All reports of hail must also include hailstone size diameter in the remarks section in increments of ¼ inches; for example, “GR less than ¼ inch.” Small hail will also result in the issuance of a SPECI. Aircraft are not permitted to operate in large hail; however, many can operate in small hail with appropriate deicing/anti-icing procedures.

“GS” will now be used only when snow pellets are observed.

John Kosak, NBAA’s Air Traffic Services, program manager of weather, explained many business aircraft operators – particularly Part 135 charter operators – do not have authority in their deicing/anti-icing programs to use holdover times as definitive guidance but do reference the information as advisory material.

“The winter flying season is upon us,” said Kosak. “Pilots and those involved in flight planning and dispatching should familiarize themselves with the new reporting codes for snow pellets and small hail as published in InFO 18011, as well as the new holdover times for 2018-2019.”

View the FAA’s Holdover Times and Allowance Guidance.