Narrative:

The ILS approach was flown terminating in a landing in the touchdown zone; on speed; and slightly left of the centerline. During landing rollout; the nose of the aircraft began a rather abrupt turn to the right which quickly developed into an uncontrollable slide and departed the right side of the runway. It continued across approximately 400 ft of unpaved surface and came to a stop on the intersection of taxiways on a heading of 140 degrees. The runway had just been plowed before our lndg and braking action readings of .39/.42/ and .46 mu were given. The wind was reported as 120 degrees at 12 KTS. There were no passengers on board; no one on the crew was injured; and the aircraft sustained no damage. In view of what happened; my conclusion is that the actual conditions were not what we had been told when we decided to proceed with our approach and landing. Either the equipment used to determine the braking action was not functioning properly; calibrated properly or the snow was falling so heavily that new accumulation had already taken place. One solution would be to ensure braking action checks are conducted as close as possible to the actual landing time of an inbound aircraft when moderate or heavier snow is falling. Another solution would be to not dispatch a flight to an airfield if its arrival time will fall within 2 hours of the forecast arrival time of a major snowstorm. A possible contributing factor may have been the right reverser not stowing as quickly as the left or all the way when the pilot flying attempted to stow the reversers to regain control. After the aircraft came to a stop; the amber reverser icon was displayed on the right N1 gauge and the emergency stow pba for the right thrust reverser was illuminated. Supplemental information from acn 816438: on final approach; told to go around because airport was closed due to plows on the runway. Flew a missed approach and switched to departure. As soon as plow was finished; we were cleared to land. I flew a coupled approach and was on speed. First officer called out all altitudes on approach. Rolled about 1000 ft before nose started to veer to right and tail to left. We then started to slide towards right side of the runway. First officer helped with the yoke. First officer said 'left rudder' at which point I confirmed to him that I already had the input. I had full left rudder and left brake. At this point we were sliding and couldn't get the aircraft to do anything we tried. We slide off the right side of the runway with nose veering to right. At this point I noticed that we had right thrust reverser indication of it not being stowed: amber reverser on N1 gauge. Amber unlock button lit on thrust reverser panel.

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Original NASA ASRS Text

Title: CL65 flight crew on a ferry flight experiences uncontrollable runway excursion. Subsequent to the event they notice the right thrust reverser failed to stow; the aircraft did not incur any damage.

Narrative: The ILS approach was flown terminating in a landing in the touchdown zone; on speed; and slightly left of the centerline. During landing rollout; the nose of the aircraft began a rather abrupt turn to the right which quickly developed into an uncontrollable slide and departed the right side of the runway. It continued across approximately 400 FT of unpaved surface and came to a stop on the intersection of taxiways on a heading of 140 degrees. The runway had just been plowed before our lndg and braking action readings of .39/.42/ and .46 MU were given. The wind was reported as 120 degrees at 12 KTS. There were no passengers on board; no one on the crew was injured; and the aircraft sustained no damage. In view of what happened; my conclusion is that the actual conditions were not what we had been told when we decided to proceed with our approach and landing. Either the equipment used to determine the braking action was not functioning properly; calibrated properly or the snow was falling so heavily that new accumulation had already taken place. One solution would be to ensure Braking Action checks are conducted as close as possible to the actual landing time of an inbound aircraft when moderate or heavier snow is falling. Another solution would be to not dispatch a flight to an airfield if its arrival time will fall within 2 hours of the forecast arrival time of a major snowstorm. A possible contributing factor may have been the right reverser not stowing as quickly as the left or all the way when the Pilot Flying attempted to stow the reversers to regain control. After the aircraft came to a stop; the amber Reverser icon was displayed on the right N1 Gauge and the Emergency Stow PBA for the right thrust reverser was illuminated. Supplemental information from ACN 816438: On Final Approach; told to go around because airport was closed due to plows on the runway. Flew a missed approach and switched to Departure. As soon as plow was finished; we were cleared to land. I flew a coupled approach and was on speed. First Officer called out all altitudes on approach. Rolled about 1000 FT before nose started to veer to right and tail to left. We then started to slide towards right side of the runway. First Officer helped with the yoke. First Officer said 'left rudder' at which point I confirmed to him that I already had the input. I had full left rudder and left brake. At this point we were sliding and couldn't get the aircraft to do anything we tried. We slide off the right side of the runway with nose veering to right. At this point I noticed that we had Right Thrust Reverser indication of it not being stowed: Amber Reverser on N1 gauge. Amber Unlock button lit on Thrust Reverser Panel.

Data retrieved from NASA's ASRS site as of May 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.