In Winter Weather Conditions-Check Fan Rotation before Engine Start
All Models ATA: 71-00
Operators are reminded that engines should be rechecked to ensure free fan rotation prior to an engine start in conditions with blowing snow, freezing rain or ice.
Aircraft moved outdoors from heated hangars should also be given special attention. The heated surfaces can cause winter precipitation to rapidly melt and then re-freeze in engine inlets as the airplane is chilled to ambient temperatures outside. Nearly every year, Citation Customer Service receives reports of frozen engine fans due to ice buildup in winter weather events.
Caution: To prevent possible engine damage from ingestion of ice, do not chip or scrape ice or snow from the engine inlet(s). Properly de-ice these areas prior to engine start. Operators can refer to Section VII of the applicable Airplane Flight Manual (AFM) for the deicing procedures.
Note: Also it is wise for operators to familiarize themselves with the cold weather engine start procedures in Section III, Operating Procedures, Normal Procedures of the applicable AFM
Source : Cessna
Qualty,Safety and Training