Dispatch and Weather
The aircraft was dispatched with an inoperable airframe deice system, although an operational deice system was required for flight in known icing conditions. The pilots had received a printout of weather from the company computer system containing surface observations and terminal forecasts, but no area forecast (FA). The area forecast had been available at the company weather terminal, but pilots and ground personnel were not aware of it. The area forecast had called for light and occasional moderate rime and mixed icing in clouds and precipitation above the freezing level.
Flight and Landing
During descent to land, the aircraft encountered light icing conditions. The captain stated he believed the aircraft could handle it and continued the descent. As he began an ILS final approach, he noted a significant increase of ice accumulation and used a higher than normal approach speed. When full (50 degrees) flaps were set, the aircraft began to buffet and pitched nose down. The captain corrected with full back pressure on the control column, but the aircraft landed hard. The landing gear collapsed, and the aircraft slid about 3,600 feet to a stop.
Investigation Findings
No preimpact mechanical anomaly was found, except for the inoperable deice system. There was evidence of a tailplane stall. The flight manual noted that tailplane ice may cause a nose-down trim change with flap extension. The investigation revealed a lack of company training in cold weather operations, deficiencies in the use of the deicing system, and a lack of FAA surveillance. Additionally, the pilots did not request in-flight weather information or pilot reports, despite deteriorating weather conditions.