Narrative:

Numerous company aircraft are deicing and taxiing out with current WX at about 1400 ft broken; 4 mi visibility; light winds; temperature 1 degree C and light ice pellets; light drizzle; and light snow. My flight is being deiced when we receive a dispatch message with this WX (basically no change). There is no mention of any illegality for our flight to continue. Several planes have taxied already and many of these only used type 1 and not type 4. The actual WX is just not that bad! The first officer and I agree that type 4 is needed; so the deice truck agrees to do it only after some hesitation. Another pilot says over the radio to check the chart; which we do and can see nothing to prevent us from leaving. Because I now have a bad feeling; I contact dispatch by voice. We are informed that our deice charts only account for 2 types of precipitation -- mdw has 3; so we are grounded. I ask then if this is something I have missed over the last 30 yrs of flying. 'Oh no; this had happened a couple of yrs ago also;' dispatch said. News to me! Another pilot now says over the radio that his dispatcher has told him not to go by ACARS. I try to solve some of the confusion by contacting operations to explain dispatch's '3 strikes you are out' interpretation. Operations wants nothing to do with this and tells me I must have dispatch do all the talking. I expected this but am hoping to convey my newly acquired information to anyone listening on operations frequency. We taxi back to the gate to wait for the WX to change as do all our other planes. While we wait; numerous aircraft land and take off -- including; I believe; other airlines. About 10 mins prior to our second push; another company flight has pushed; deiced; and requested taxi for takeoff without having the '3 strikes' removed from the ATIS. WX goes to 2 items and we push and deice again. Once again there is a lot of chatter on the radio about if type 4 is required. I think we all get type 4 and depart. Our deice charts do not clearly define this '3 strikes' situation as no-go. Maybe; because it never has been before. We always deiced to the worst condition and went from there. If this is a 'law' -- then spell it out. If not; then fix 'our' rules to allow for traditional worst case deice and go.

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Original NASA ASRS Text

Title: B737-700 CAPTAIN REPORTS THAT COMPANY DEICING REGS FAIL TO ADDRESS SITUATIONS WHERE MORE THAN TWO FORMS OF REPORTED PRECIPITATION MUST BE ACCOUNTED FOR IN THE DETERMINATION OF TYPES OF FLUID REQUIRED AND HOLDOVER TIMES.

Narrative: NUMEROUS COMPANY ACFT ARE DEICING AND TAXIING OUT WITH CURRENT WX AT ABOUT 1400 FT BROKEN; 4 MI VISIBILITY; LIGHT WINDS; TEMP 1 DEG C AND LIGHT ICE PELLETS; LIGHT DRIZZLE; AND LIGHT SNOW. MY FLT IS BEING DEICED WHEN WE RECEIVE A DISPATCH MESSAGE WITH THIS WX (BASICALLY NO CHANGE). THERE IS NO MENTION OF ANY ILLEGALITY FOR OUR FLT TO CONTINUE. SEVERAL PLANES HAVE TAXIED ALREADY AND MANY OF THESE ONLY USED TYPE 1 AND NOT TYPE 4. THE ACTUAL WX IS JUST NOT THAT BAD! THE FO AND I AGREE THAT TYPE 4 IS NEEDED; SO THE DEICE TRUCK AGREES TO DO IT ONLY AFTER SOME HESITATION. ANOTHER PLT SAYS OVER THE RADIO TO CHK THE CHART; WHICH WE DO AND CAN SEE NOTHING TO PREVENT US FROM LEAVING. BECAUSE I NOW HAVE A BAD FEELING; I CONTACT DISPATCH BY VOICE. WE ARE INFORMED THAT OUR DEICE CHARTS ONLY ACCOUNT FOR 2 TYPES OF PRECIP -- MDW HAS 3; SO WE ARE GROUNDED. I ASK THEN IF THIS IS SOMETHING I HAVE MISSED OVER THE LAST 30 YRS OF FLYING. 'OH NO; THIS HAD HAPPENED A COUPLE OF YRS AGO ALSO;' DISPATCH SAID. NEWS TO ME! ANOTHER PLT NOW SAYS OVER THE RADIO THAT HIS DISPATCHER HAS TOLD HIM NOT TO GO BY ACARS. I TRY TO SOLVE SOME OF THE CONFUSION BY CONTACTING OPS TO EXPLAIN DISPATCH'S '3 STRIKES YOU ARE OUT' INTERP. OPS WANTS NOTHING TO DO WITH THIS AND TELLS ME I MUST HAVE DISPATCH DO ALL THE TALKING. I EXPECTED THIS BUT AM HOPING TO CONVEY MY NEWLY ACQUIRED INFO TO ANYONE LISTENING ON OPS FREQ. WE TAXI BACK TO THE GATE TO WAIT FOR THE WX TO CHANGE AS DO ALL OUR OTHER PLANES. WHILE WE WAIT; NUMEROUS ACFT LAND AND TAKE OFF -- INCLUDING; I BELIEVE; OTHER AIRLINES. ABOUT 10 MINS PRIOR TO OUR SECOND PUSH; ANOTHER COMPANY FLT HAS PUSHED; DEICED; AND REQUESTED TAXI FOR TKOF WITHOUT HAVING THE '3 STRIKES' REMOVED FROM THE ATIS. WX GOES TO 2 ITEMS AND WE PUSH AND DEICE AGAIN. ONCE AGAIN THERE IS A LOT OF CHATTER ON THE RADIO ABOUT IF TYPE 4 IS REQUIRED. I THINK WE ALL GET TYPE 4 AND DEPART. OUR DEICE CHARTS DO NOT CLEARLY DEFINE THIS '3 STRIKES' SITUATION AS NO-GO. MAYBE; BECAUSE IT NEVER HAS BEEN BEFORE. WE ALWAYS DEICED TO THE WORST CONDITION AND WENT FROM THERE. IF THIS IS A 'LAW' -- THEN SPELL IT OUT. IF NOT; THEN FIX 'OUR' RULES TO ALLOW FOR TRADITIONAL WORST CASE DEICE AND GO.

Data retrieved from NASA's ASRS site as of May 2009 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.