AN ACR LGT CAPT TOOK OFF WITH A LIGHT DUSTING OF SNOW ON HIS WINGS. THE ACFT WAS OTHERWISE CLEAN. ERROR ADMITTED.

Narrative

DURING APCH AND LNDG; NO PRECIP. LNDG AND TAXI IN WERE NORMAL ALTHOUGH TXWYS WERE SLICK DUE TO COMPACTED SNOW. AS PAX WERE DEPLANING; A LIGHT SNOW SHOWER ARRIVED AND LASTED FOR A SHORT TIME. I RETURNED TO THE ACFT APPROX 30 MINS BEFORE DEP. THE SNOW HAD STOPPED FALLING. I ASKED THE SO IF THERE WAS SNOW ON THE ACFT AND A NEED FOR DEICING. HE SAID THERE WAS NO SNOW ON THE ACFT EXCEPT FOR A LITTLE ON TOP OF THE WING. HE THOUGHT THERE WAS NO NEED TO DEICE AS THE TEMP WAS APPROX 20 DEGS F; WITH ONLY A LITTLE LIGHT SNOW ON TOP OF THE WING WHICH WAS NOT STICKING AS HE HAD CHKED IT WITH HIS HAND. I INSPECTED THE ACFT AND FOUND IT TO BE AS DESCRIBED. THE FUSELAGE; ENGS; TAIL; LEADING EDGE AND UNDER WING WERE CLEAN AND DRY. THERE WAS A DUSTING ON TOP OF THE COLD WING WHICH WAS NOT STICKING AND WOULD EASILY BLOW OFF. I AGREED THERE WAS NO NEED TO DEICE. AS WE TAXIED FOR TKOF I SAW A FEW ACFT BEING DEICED. WE MADE A NORMAL TKOF WITH ENG ANTI-ICE ON. THE QUESTION OCCURRED TO ME LATER -- WAS THERE SOMETHING I DIDN'T THINK OF? I CONSULTED THE OPERATING MANUAL AND FOUND IT STATES THAT WITH THE 'CLEAN ACFT CONCEPT;' THE ACFT MUST BE FREE OF ICE AND SNOW (FROM ANY CONTAMINATION) PRIOR TO TKOF. I KNEW THIS; YET I THOUGHT I WOULD MAKE A JUDGEMENT IN A SIT AS THIS ONE THAT IS NOT ALLOWED. I SHOULD HAVE DEICED. I HAD ERRED BY SLIPPING INTO THE WAY WE 'USED TO DO IT.'