On October 31, 1994, at 1559 Central Standard Time, an Avions de Transport Regional, model 72-212 (ATR 72), registration number N401AM, leased to and operated by Simmons Airlines, Incorporated, and doing business as American Eagle flight 4184, crashed during a rapid descent after an uncommanded roll excursion. The airplane was in a holding pattern and was descending to a newly assigned altitude of 8,000 feet when the initial roll excursion occurred. The airplane was destroyed by impact forces; and the captain, first officer, 2 flight attendants and 64 passengers received fatal injuries. Flight 4184 was a regularly scheduled passenger flight being conducted under 14 Code of Federal Regulations, Part 121; and an instrument flight rules flight plan had been filed.
Clear ice is a glossy, clear-to-translucent accumulation formed by large water droplets or raindrops which spread and freeze on contact, forming a sheet of smooth ice
The National Transportation Safety Board determines that the probable causes of this accident were the loss of control, attributed to a sudden and unexpected aileron hinge moment reversal that occurred after a ridge of ice accreted beyond the deice boots because:
1) ATR failed to completely disclose to operators, and incorporate in the ATR 72 airplane flight manual, flight crew operating manual and flightcrew training programs, adequate information concerning previously known effects of freezing precipitation on the stability and control characteristics, autopilot and related operational procedures when the ATR 72 was operated in such conditions;
2) the French Directorate General for Civil Aviation’s inadequate oversight of the ATR 42 and 72, and its failure to take the necessary corrective action to ensure continued airworthiness in icing conditions; and
3) the French Directorate General for Civil Aviation’s failure to provide the Federal Aviation Administration with timely airworthiness information developed from previous ATR incidents and accidents in icing conditions, as specified under the Bilateral Airworthiness Agreement and Annex 8 of the International Civil Aviation Organization.
Contributing to the accident were:
1) the Federal Aviation Administration’s failure to ensure that aircraft icing certification requirements, operational requirements for flight into icing conditions, and Federal Aviation Administration published aircraft icing information adequately accounted for the hazards that can result from flight in freezing rain and other icing conditions not specified in 14 Code of Federal Regulations, Part 25, Appendix C; and
2) the Federal Aviation Administration’s inadequate oversight of the ATR 42 and 72 to ensure continued airworthiness in icing conditions.