LOSS OF ACFT CTL DURING TAXI RAMP OP DUE TO RAMP CONDITIONS ICE.

Narrative

FLT FROM KBOS TO KBGA. BGR TEMP WAS 37 DEG WITH MODERATE RAIN. WE WERE SURPRISED TO FIND KBGR HAD JUST BEEN CLOSED UPON OUR ARR IN LCL AREA. CLOSURE WAS DUE TO NEED TO REMOVE ICE AND SNOW FROM RWY. ALTHOUGH ABOVE FREEZING; WE LEARNED LATER ARPT SURFACES WERE BELOW FREEZING DUE TO RECENT EXTENDED BELOW 0 DEG TEMPS. UPON RESUMPTION OF OPS BGR RPTED RWY CLR AND WET 75 FT EITHER SIDE OF CENTER. LNDG WAS COMPLETED WITH NO BRAKING PROBLEMS. TWR ADVISED US TO TAXI TO END AND FOLLOW TAXI LINES TO RAMP. A VERY SLOW TAXI WAS ACCOMPLISHED WITH NO PROBLEMS. RAMP WAS RPTED AS BRAKING FAIR TO POOR BY A TRUCK. TURN INTO GATE WOULD REQUIRE ABOUT A 140 DEG TURN DUE TO ALIGNMENT OF JETWAY. TAXI WAS PLANNED TO LEAVE AS MUCH ROOM AS POSSIBLE FOR A WIDE TURN. TAXI ON RAMP WAS UNEVENTFUL UNTIL ATTEMPTING TO BEGIN R TURN INTO GATE. NOSE GEAR BEGAN SLIDING L WHILE MAINS SKIDDED R. ATTEMPTS TO CTL SKIDDING WITH THRUST WAS NOT EFFECTIVE. ACFT CAME TO REST AFTER TURNING ABOUT 30 DEG TO THE L. AT THIS TIME A TUG EQUIPPED WITH CHAINS WAS CONNECTED TO TOW ACFT TO GATE. INITIAL TOWING WAS SUCCESSFUL. HOWEVER A GUST OF WIND CAUGHT ACFT TAIL AND BOTH TUG AND ACFT BEGAN SKIDDING. ACFT AND TUG STOPPED AFTER ACFT AND TUG TURNED ANOTHER 10-20 DEGS. TEMP WAS NOW RISING RAPIDLY AND RAIN HAD BECOME HVY. WE ELECTED TO WAIT FOR ICE TO MELT. AFTER ABOUT 1 HR RAMP CONDITIONS HAD IMPROVED ENOUGH FOR TUG TO TOW ACFT TO GATE. THIS WAS A VERY SERIOUS SITUATION WITH A HIGH POTENTIAL FOR ACFT DAMAGE OR INJURY TO CREW OR PAX. WE TAXIED ACFT INTO AN AREA THAT HAD NOT BEEN SCRAPED CLEAN OF ICE. AFTER BEING REASSURED BY THE VERY GOOD CONDITION OF RWY AND TAXIWAYS; THE RAMP APPEARED TO BE TOTALLY CLR OF ICE. PATIENCE AND EXTREME ATTN TO SAFETY BY GND AND FLC PREVENTED A BAD SITUATION FROM DETERIORATING INTO AN ACCIDENT.