Date: 201603
Local time of day: 1801-2400
Location: DTW.Airport, MI
Flight conditions: Marginal
Weather elements / visibility: Snow
Light: Night
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Other / Unknown
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew Took Evasive Action
Contributing factors: Human Factors; Procedure; Weather; Company Policy; Airport
Primary problem: Airport

Narrative: Upon arriving at the gate there were no personnel to guide us in. The taxi inline was covered in snow. After a few minutes rampers appeared in tugs and on foot. The ramp was slippery as indicated by a ramper falling down after slipping. The tugs were sliding as well. We waited a few more minutes to be marshaled in. Finally the marshals showed up and we proceeded into the gate indicating 1 knot on the ground speed readout on the Navigation Display (ND). I was purposely very cautious on the taxi in. We were given the stop signal as normally presented and set the brakes. The aircraft continued to slide forward even though the brakes were set. The residual thrust at idle was enough to move the aircraft on the ramp under these conditions. The aircraft was not going to hit anything or anyone but I was helpless at this point. I indicated to the marshaller to get the chocks in. He didn't have any!!! I turned on the yellow pump and decided to shut down the engines in the hopes the loss of the residual thrust would help. It did. The aircraft stopped sliding. What a helpless feeling.Do I go into reverse and blow equipment and people around? We thought the best thing to do was just shut it down. The rampers were quick to open the cargo door creating another obstacle. During the walk around the First Officer (FO) verified that the brakes were set and all the landing gears were plowing the snow in front of them instead of rolling over it. The event occurred because the ramp was in no condition to receive this aircraft. We couldn't tell anything of its surface condition. Chocks should have been at the gate instead of waiting for them to show up from another gate. I could have at least gotten the chocks installed quicker at the gate. We were lucky that nothing was touched or damaged. Fortunately the jetway was very far away from its normal position.In the future I recommend a cursory check of the gate arrival area prior to an arriving aircraft given the fact that the snow was falling during this time. I feel the rampers were not prepared to receive us and we should have been left way off the gate till they were truly ready with chocks in hand. After the event occurred and we were stopped I later wondered if stopping and shutting down way off the gate and being towed in would have been a better idea. After the FO came back up after the post flight and described the ramp conditions (he fell himself on the ramp walking very diligently) even a tow in would not have worked. Could have been worse. In the future I will not follow the marshallers instructions to taxi in when we recognize a similar situation. I would shut it down or go to a gate prepared for our arrival.




Synopsis: An A320 Captain encountered extremely slippery ramp conditions and a lack of preparation by the ground crew during gate arrival at DTW. When the stop signal is received the brakes are set; but the aircraft continues to move forward due to slippery conditions and residual thrust. The engines are quickly shut down and the aircraft stops sliding.