Accident Overview
An aircraft was dispatched with an inoperative airframe deice system, although operational deice capability was required for flight in known icing conditions. During descent for landing, the aircraft encountered light icing conditions. The captain believed the aircraft could handle the conditions and continued the descent.
Sequence of Events
As the captain began an ILS final approach, he noted a significant increase in ice accumulation and opted to use a higher than normal approach speed. When full flaps (50°) were set, the aircraft began to buffet and pitched nose down. The captain applied full back pressure on the control column, but the aircraft landed hard. The landing gear collapsed, and the aircraft slid approximately 3,600 feet before stopping.
Investigation Findings
No preimpact mechanical anomalies were found, except for the inoperative deice system. The investigation revealed that the pilots had received a printout of weather from the company computer system, including surface observations and terminal forecasts, but no area forecast (FA). Both pilots and ground personnel were unaware that the FA was available at the company weather terminal. The FA had forecast light and occasional moderate rime and mixed icing in clouds and precipitation above the freezing level. Weather conditions deteriorated, but the pilots did not request inflight weather information or pilot reports (PIREPs).
The flight manual noted that tailplane ice could cause a nose-down trim change upon flap extension. Evidence indicated a tailplane stall. The investigation also cited a lack of company training in cold weather operations, deficiencies in the use of deicing systems, and a lack of FAA surveillance.