B767-300 LOST DIRECTIONAL CONTROL OF ACFT WHILE TAXIING ON SNOW COVERED TXWY. ACFT STOPPED AND TUG REQUESTED.

Narrative

FOLLOWING LOADING ACFT WAS DEICED THEN ANTI-ICED. OBTAINED CLRNC; BLOCKED OUT; STARTED ENGS; AND BEGAN TAXIING. ATIS RPTED TXWYS 100% COVERED WITH LOOSE COMPACTED SNOW LESS THAN 1/2 INCH THICK. TXWY CONDITION RPTED POOR BY VEHICLE. SNOWFALL CONTINUED AND ALL RAMPS AND TXWYS WERE OBSERVED COVERED WITH SNOW. WE TAXIED SLOW. INCIDENT INFO: WE TAXIED UP A SLIGHT GRADIENT ON TXWY E. WE BEGAN A R TURN ONTO TXWY A. THE ACFT BEGAN TO SLIDE SLIGHTLY AND RESISTED TURNING. THE CAPT USED DIFFERENTIAL THRUST (APPLIED PWR TO THE L ENG) TO ENABLE THE R TURN. THE ACFT TURNED TO THE R AND THE CAPT REDUCED PWR ON THE L ENG TO IDLE. THE ACFT CONTINUED TURNING TO THE R SLIDING PAST THE ALIGNMENT FOR TXWY A. THE CAPT APPLIED BRAKES AND USED REVERSE THRUST TO STOP THE ACFT. THE ACFT STOPPED AND WAS POINTING OFF TXWY A NEAR THE R EDGE. WE RPTED THE INCIDENT TO GND CTL AND THEY TOLD US TO CONTACT OPS TO GET A TUG. ADDITIONAL INFO: DISPATCH WAS NOTIFIED WE WERE STUCK IN THE SNOW. MAINT ARRIVED 10-15 MINS LATER. THEY BROUGHT A TUG; SNOWPLOW AND SOME ADDITIONAL EQUIP. WE SHUT DOWN BOTH ENGS. THE SNOWPLOW REMOVED SNOW IN FRONT OF THE NOSEWHEEL AND PREPARED A CLR AREA FOR THE TUG. MAINT INSPECTED THE TXWY AND ENSURED NO TAXI LIGHTS WERE DAMAGED. THEY ALSO LOOKED OVER THE ACFT AND ENSURED NO DAMAGE OCCURRED TO THE MAIN OR NOSE LNDG GEAR OR ANY OTHER PART OF THE ACFT. THEY OBSERVED OUR POS ON THE TXWY. MAINT CONNECTED THE TUG AND PUSHED THE ACFT TO THE CTR OF TXWY A WITH CORRECT ALIGNMENT. WE RESTARTED BOTH ENGS; RAN ALL APPROPRIATE CHKLISTS; PROCEEDED TO TAXI AND CONTINUED TO DEST.