Narrative:

Aircraft was in level cruise flight with autoplt engaged, at FL190. Captain and I both felt a vibration through the floorboards. We both slid our seat forward and captain turned on the inspection lights. Wings, propeller spinner, and engine inlets did not appear to have excessive amounts of ice. About 30 seconds after first vibration, the stick shaker fired and captain took control of aircraft. Captain called for all anti-ice equipment on. I called mem center to tell them we were descending. The aircraft did not respond to rudder/elevator inputs. Was in a right bank, nose down at about 1000 FPM. Center cleared us to a lower altitude at about 16000 ft we regained control of aircraft and proceeded to a VFR landing at fsm. We believed we encountered a freak patch of severe icing and iced up to T tail on the aircraft, stalling the T tail. Mem center did not appear interested in our report of severe ice or our message that we were coming down! Contributing factors: late at night, fatigue. An example of an airport 135 schedule 'legal but not safe.' our first reaction was either a structural problem or a propeller overspd. We lost valuable time before we figured it out. When we turned on the de-ice boots, we got a failure light on the rudder and elevator boots.

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Original NASA ASRS Text

Title: COMMUTER LTT ENCOUNTERED ICING CONDITIONS AT CRUISE ALT AT NIGHT WITHOUT ANTI-ICE EQUIP OPERATING. ACFT DEVELOPED A VIBRATION AND THEY LOST 1000 FT BEFORE REGAINING CTL OF THE ACFT.

Narrative: ACFT WAS IN LEVEL CRUISE FLT WITH AUTOPLT ENGAGED, AT FL190. CAPT AND I BOTH FELT A VIBRATION THROUGH THE FLOORBOARDS. WE BOTH SLID OUR SEAT FORWARD AND CAPT TURNED ON THE INSPECTION LIGHTS. WINGS, PROP SPINNER, AND ENG INLETS DID NOT APPEAR TO HAVE EXCESSIVE AMOUNTS OF ICE. ABOUT 30 SECONDS AFTER FIRST VIBRATION, THE STICK SHAKER FIRED AND CAPT TOOK CTL OF ACFT. CAPT CALLED FOR ALL ANTI-ICE EQUIP ON. I CALLED MEM CENTER TO TELL THEM WE WERE DSNDING. THE ACFT DID NOT RESPOND TO RUDDER/ELEVATOR INPUTS. WAS IN A R BANK, NOSE DOWN AT ABOUT 1000 FPM. CENTER CLRED US TO A LOWER ALT AT ABOUT 16000 FT WE REGAINED CTL OF ACFT AND PROCEEDED TO A VFR LNDG AT FSM. WE BELIEVED WE ENCOUNTERED A FREAK PATCH OF SEVERE ICING AND ICED UP TO T TAIL ON THE ACFT, STALLING THE T TAIL. MEM CENTER DID NOT APPEAR INTERESTED IN OUR RPT OF SEVERE ICE OR OUR MESSAGE THAT WE WERE COMING DOWN! CONTRIBUTING FACTORS: LATE AT NIGHT, FATIGUE. AN EXAMPLE OF AN ARPT 135 SCHEDULE 'LEGAL BUT NOT SAFE.' OUR FIRST REACTION WAS EITHER A STRUCTURAL PROBLEM OR A PROP OVERSPD. WE LOST VALUABLE TIME BEFORE WE FIGURED IT OUT. WHEN WE TURNED ON THE DE-ICE BOOTS, WE GOT A FAILURE LIGHT ON THE RUDDER AND ELEVATOR BOOTS.

Data retrieved from NASA's ASRS site as of July 2007 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.