With 17 passengers and 2 crew, a British Aerospace 3101 Jetstream 31 was operating a scheduled passenger flight from Charlotte-Douglas Airport (North Carolina, USA) to Beckley Airport (West Virginia) on this winter day in aviation history.
A British Aerospace 3101 Jetstream 31, not the incident aircraft (© PeteCaz)
The aircraft was dispatched with a defective airframe de-ice system in accordance with the aircraft Minimum Equipment List. This allowed the aircraft to operate with a defective airframe de-ice system as long as it was not operated into known or forecast icing conditions. After an uneventful flight, the aircraft started its descent towards Beckley Airport just before it encountered light icing, which the captain believed would not be a problem.
1995 version of the FAA-approved Master Minimum Equipment List (Source public domain)
At the Final Approach Fix for the ILS approach, the captain observed a significant increase in ice accumulation. and decided to fly the rest of the approach at a higher than normal approach speed to compensate for the ice built up. However, when the flaps were selected to 50 degrees (Landing Configuration) the aircraft began to buffet and pitched nose down sharply.
Diagram showing effect of flap position on tailplane angle of attack and
aircraft pitch attitude (Source British Aerospace - 'Think ice')
The captain attempted to correct the nose down pitch by full back pressure on the control column. This had no effect and the aircraft touched down hard, the landing gear collapsed and the aircraft slid for approximately 3600 feet (~1100 meters) before coming to a stop. A fire broke out but all passengers and crew managed to evacuate the aircraft. Of the 19 occupants, 16 are injured in varying severity. The aircraft was damaged beyond repair The incident was investigated by the NTSB and the following findings were recorded in the report (which is available by clicking here);
The crew did not make proper use of the pre-flight briefing facilities
There were training deficiencies
The FAA was lacking oversight over the operator
The flight was operated with a defective de-icing system
The flight was operated into adverse weather
The icing on the wing and stabiliser caused an aerodynamic stall
In 2014 British Aerospace published a brochure named "Think Ice" which gives a good insight into the effect of icing on British Aerospace aircraft. This document is available by clicking on the link below.