On January 14, 1999, about 1930 Eastern Standard Time, a Cessna 421B, N882BB, was substantially damaged when it slid off the runway during landing roll at the Youngstown-Warren Regional Airport (YNG), Youngstown, Ohio. The certificated commercial pilot and four passengers were not injured. Instrument meteorological conditions prevailed and an instrument flight rules flight plan was filed for the flight conducted under 14 CFR Part 135. The flight originated from the Michiana Regional Transportation Center Airport (SBN), South Bend, Indiana, about 1806. The pilot stated that the controllers relayed recent Pilot Weather Reports (PIREPS), with the braking action on the runway reported as "POOR". The pilot flew the instrument landing system (ILS) approach and was out of instrument meteorological conditions about 500 feet AGL. After touching down within the first 1,200 feet of the 9,000 foot runway, the pilot recalled that he "experienced a normal rollout for the first 2-3 seconds, then the airplane hit something." He stated that the bump was violent enough that the passengers yelled, and he thought that the nose landing gear had collapsed. The pilot applied right rudder and brake, but it was ineffective and the airplane veered off of the left side of the runway, about 3,700 feet from the threshold, impacting a 2 foot high snow bank. The Director of Aviation, for the Western Reserve Port Authority at Youngstown-Warren Regional Airport, was on scene within 30 minutes. He reported that he drove the length of the runway and found the conditions no different than what had been prevalent for the preceding week. He stated "the runway had no ruts, bumps, or holes in it. Plowing trims off all loose snow leaving only a thin (less than 1/2 inch) layer of patchy packed snow over ice." A Federal Aviation Administration Inspector examined the wreckage and the runway condition 2 hours after the accident. His examination revealed that the left main landing gear separated from the airplane damaging the left wing spar. The nose landing gear collapsed and both propellers struck the runway. The Inspector reported that because of the severe weather and the numerous tracks from the emergency/snow removal vehicles, he was not able to make an accurate assessment of the "locality of the bump felt by the crew and passengers" on the ice and snow covered runway. A witness stated that the airplane was in a steep angle of descent as it broke out of the clouds. He added that the airplane may have been in a slip. The reported weather at YNG at the time of the accident was: wind from 300 degrees at 5 knots; visibility 1 1/2 miles, light freezing rain ice pellets, mist; ceiling 400 feet overcast; temperature 19 degrees Fahrenheit, dewpoint 18 degrees; altimeter 30.03 inches Hg. The airport Notice to Airman stated "Runway 14/32 plowed [and] sanded covered with hard packed snow over thin ice BRAP [braking action reported as poor]..."