Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP)
Confusion; Situational Awareness
Ground Event / Encounter Loss Of Aircraft Control; Ground Event / Encounter Vehicle
Aircraft Aircraft Damaged; General Maintenance Action
Airport; Human Factors; Weather
Icy conditions on ground in MSN. Went very slow during taxi; no problems on the taxiways. We proceeded with extreme caution and discussed hazards. Turning into gate; it looked a bit icy but was hard to tell. Was taking it very slow; doing about 5 kts lined up with marshaller. Were told to come forward; tried to apply brakes to try to slow a little more; but aircraft would not stop. At that time; noticed that they told us to stop. Let off the brakes and reapplied full brakes; (braking action nil although no report available at that time) but they were ineffective and the aircraft kept sliding forward. Saw that we were not going to stop; and braced for impact. Ended up hitting the tug. We followed all company procedures and guidance as well as instruction from ramp personnel. FO was helping me out and was trying to apply brakes also. Heard him say thrust reversers; hesitated because we are instructed to not use them on taxi. Did pop them for about 1 second to try to help us stop due to emergency situation of trying to avoid hitting the ground equipment.With clear ice on the ramp; we could not determine how slick it was till we got off the aircraft. They had to sand/salt the ramp area just to be able to tug us back into the parking space. They also had to move the stairs by hand. Crew reviewed all info in relating to conditions at MSN. We also got a ground report for taxiways upon arrival from an airport operations vehicle. He did not have a report of our ramp conditions.
[Report narrative contained no additional information.]
Air carrier flight crew reported unanticipated icy ramp conditions while parking their aircraft at the gate. They were unable to stop the aircraft before hitting a tug vehicle.