Narrative:

The ATIS we had when beginning taxi to the deice pad was: xa:53Z wind 070/07 3/4 -sn br -07/-09 30.10. While type iv was being applied; I got the new ATIS: xc:34Z wind 070/06 1/2 sn fzfg -07/-09 30.11. I consulted the FAA type iv holdover time guidelines table and saw one column for 'freezing fog' and a separate column for 'snow; snow grains or snow pellets.' since the current conditions included both freezing fog and snow; I was unsure what published holdover time to use and suspected that dispatch would not be allowed because there was no published holdover time for this combination of weather conditions. We taxied out of the pad then told ATC we needed to stop and call the company. I first explained our situation to dispatch. Dispatch checked their manuals and said that the only mention of combined meteorological conditions precluding the use of any published chart concerned the 'snowfall intensities as a function of prevailing visibility' chart. So; in dispatch's opinion; we could use the more restrictive of the holdover times for freezing fog or snow and depart. Then I explained our situation to the chief pilot. According to him; the FAA was informed of our company's intent to operate in combined meteorological conditions by using the most restrictive time listed in the applicable columns of the holdover table. He said that the FAA would neither approve that procedure nor prevent the company from operating in that manner. When I said that sounded a little odd; he told me that it was a liability issue. Then I explained our situation and the company's position to the union. The union representative said that he would call me back. He called back after having discussed the issue with X safety organization and said that no holdover time existed for our freezing fog and snow combination; and that if we chose to depart we would be test pilots. However; he also said that the union would support me whether I decided to depart or not. About this time the flight attendant called because one of our passengers wanted off of the plane. So; we returned to the gate to let him off and were told that dispatch had cancelled the flight. If the applicable holdover time table does not address your particular combination of meteorological conditions; then consult the column titled 'other.' it says; 'caution: no holdover time guidelines exist.' then consult the company note that says; 'warning: when sae type iv fluid has been applied; dispatch is prohibited in conditions of heavy ice pellets; snow pellets; moderate and heavy freezing rain; hail or conditions where no holdover time exists.'

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Original NASA ASRS Text

Title: An Air Carrier flight was canceled after the crew discovered that the FAA TYPE IV HOLDOVER TIME GUIDELINES did not cover combined conditions that included FZFG and Snow; Snow Grains or Snow pellets.

Narrative: The ATIS we had when beginning taxi to the deice pad was: XA:53Z wind 070/07 3/4 -SN BR -07/-09 30.10. While Type IV was being applied; I got the new ATIS: XC:34Z wind 070/06 1/2 SN FZFG -07/-09 30.11. I consulted the FAA TYPE IV HOLDOVER TIME GUIDELINES table and saw one column for 'Freezing Fog' and a separate column for 'Snow; Snow Grains or Snow Pellets.' Since the current conditions included both Freezing Fog and Snow; I was unsure what published holdover time to use and suspected that Dispatch would not be allowed because there was no published holdover time for this combination of weather conditions. We taxied out of the pad then told ATC we needed to stop and call the company. I first explained our situation to Dispatch. Dispatch checked their manuals and said that the only mention of combined meteorological conditions precluding the use of any published chart concerned the 'Snowfall Intensities as a Function of Prevailing Visibility' chart. So; in Dispatch's opinion; we could use the more restrictive of the holdover times for Freezing Fog or Snow and depart. Then I explained our situation to the Chief Pilot. According to him; the FAA was informed of our company's intent to operate in combined meteorological conditions by using the most restrictive time listed in the applicable columns of the holdover table. He said that the FAA would neither approve that procedure nor prevent the company from operating in that manner. When I said that sounded a little odd; he told me that it was a liability issue. Then I explained our situation and the company's position to the Union. The Union Representative said that he would call me back. He called back after having discussed the issue with X Safety organization and said that no holdover time existed for our Freezing Fog and Snow combination; and that if we chose to depart we would be test pilots. However; he also said that the Union would support me whether I decided to depart or not. About this time the Flight Attendant called because one of our passengers wanted off of the plane. So; we returned to the gate to let him off and were told that Dispatch had cancelled the flight. If the applicable holdover time table does not address your particular combination of meteorological conditions; then consult the column titled 'Other.' It says; 'CAUTION: No holdover time guidelines exist.' Then consult the company note that says; 'WARNING: When SAE Type IV fluid has been applied; dispatch is prohibited in conditions of heavy ice pellets; snow pellets; moderate and heavy freezing rain; hail or CONDITIONS WHERE NO HOLDOVER TIME EXISTS.'

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.