DC-10 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Loss Of Aircraft Control
Flight Crew Regained Aircraft Control; General Maintenance Action
Airport; Human Factors
Aircraft was scheduled for a morning takeoff. Temperature was just above freezing in snow/icing conditions. After engine start and tug push/disconnect; the Captain began moving the [aircraft] over what appeared to be slush and snow on the taxiway. Under that snow and slush proved to be an unobservable layer of ice. On his first attempt to turn; the aircraft did not respond to steering or brake inputs and began sliding. Snow and ice hindered the Captain's control of this slow moving aircraft for several seconds and several feet of motion. With no braking or steering capability; the Captain utilized thrust reversers to finally stop the aircraft. IAD experienced a heavy snow fall the day before this event. On the morning of departure; surface conditions around the aircraft were covered in slush and snow. Temperatures were above freezing and there was a subtle drizzle. Company ramp was plowed but still had what appeared to be a thin layer of mixed elements. Taxi markings were visible. Crew conducted normal engine start and tug disconnect. When ready; the Captain began to taxi at a conservative pace. While attempting to make his first turn; the aircraft did not respond to tiller inputs. Aircraft began to slide on a gradual diagonal to the intended path of movement. Captain attempted to stop aircraft using brakes with no response. Speed of the slide was at the pace of a person's walk. Aircraft did not accelerate but did not slow. With no other options; the Captain applied reverse thrust to stop the aircraft. After sliding several feet; aircraft came to a stop. Contacted ramp representatives and had the ramp deiced before safely continuing the taxi. Maintenance inspected the aircraft and noted no damage to the aircraft or any equipment. Quick thinking of the Captain prevented this event from becoming costly.   Proper snow removal is imperative. Although the area around the aircraft was covered in slush; the remainder of the ramp spaces proved to be solid ice covered in a light rain and snow. If company is responsible for ice removal; they must aggressively ensure safe conditions for taxiing on the ramp beyond parking spaces. If ground crews recognize an excessive sliding in the tug; it must be shared to proactively mitigate any threats to the crew they are pushing. In this case; the crew was properly rested and ready to deal with the adverse weather conditions. With a fatigued; distracted; or unexperienced crew; this event could have damaged the aircraft or equipment.
Wide-Body Transport FO reported they encountered extremely slippery conditions on taxi out that necessitated the use of reverse thrust to come to a stop.