Date: 201302
Local time of day: 0601-1200
Location: DEN.Airport, CO
Weather elements / visibility: Icing; Snow
Light: Daylight
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ramp DEN
Aircraft component: Turbine Engine Thrust Reverser
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Troubleshooting; Workload; Situational Awareness; Training / Qualification
Anomaly: Aircraft Equipment Problem Less Severe; Ground Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Loss Of Aircraft Control
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: Taxi
Result: Flight Crew Returned To Gate; General Maintenance Action
Contributing factors: Weather; Aircraft
Primary problem: Ambiguous

Narrative: Snow in Denver. We began our pushback and stopped about 25 feet off the gate as snow removal was in progress behind us on the ramp. Normal pushback to freshly cleaned ramp. Tug driver asked me to set brakes; which I did. We started both engines due to contaminated ramp. After disconnecting the tow bar; the tug driver again asked me to set my brakes. I confirmed they were set and told him so. He informed me we were sliding forward. The tug was still under our nose so I popped open the reversers into idle reverse to stop forward thrust/motion which stopped our sliding. The tug driver confirmed we were stopped and I cleared him off the headset so he could move away from the aircraft. We were cleared to taxi and since there was not much room to turn (only a right turn was possible) I left the #2 engine in idle reverse and turned the tiller to the right with slight forward thrust on the #1 engine to help the turn (right 270 degrees turn required). My thought process was; since we had already slid on the ramp; the nosewheel could very well slide in the turn if we had forward thrust on both engines. At a slow crawl we began to move at which time I took the #2 engine out of idle reverse and into idle forward thrust. After about 180 degrees of turn the First Officer pointed at the #2 engine instrument (center DU) which indicated the #2 reverser was unlocked - even though the reverser handle was down. I then cycled the #2 engine into idle reverse and then back to idle forward thrust at which time the reverser light on the center DU extinguished. We deiced following the QRH deicing procedures and proceeded to Runway 34L. When I called for the Before Takeoff Checklist; the First Officer did a recall check at which time the ENG light illuminated on the six pack. We looked for an Amber light and found the #2 engine reverser light illuminated on the back right portion of the overhead panel. We reviewed the QRH for this light and then returned to the gate. Maintenance personnel cleared the computer; checked the reverser; and cleared us to go. We taxied out; deiced again; and departed Denver.




Synopsis: A B737 Captain used reverse thrust in the ramp area to halt sliding on ice near the pushback tug and then returned to the gate when the thrust reverser did not indicate completely stowed.