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American Eagle Flight 4184 was a regional airline flight that crashed after flying into known icing conditions on October 31, 1994. Control was lost and all aboard were killed.

Contents 1 History 2 Cause 3 Aftermath 4 Dramatization 5 External links

The aircraft, N401AM, was an ATR 72-212 operated by Simmons Airlines on behalf of American Eagle (a subsidiary of the AMR Corporation). The flight was en route from Indianapolis International Airport, Indiana to O'Hare International Airport, Chicago, Illinois. Bad weather in Chicago caused delays, prompting air traffic control to hold Flight 4184 over the nearby LUCIT intersection at 10,000 ft.

While holding, they encountered freezing rain — a dangerous icing condition where supercooled droplets rapidly cause intense ice buildup. Soon after, they were cleared to descend to 8,000 ft. During this descent the aircraft experienced an uncommanded roll excursion, which disengaged the autopilot. Flight recorder data showed that it subsequently went through at least one full roll, and the crew was unable to regain control of the rapidly descending aircraft. Less than two minutes later, contact was lost as the plane impacted a soybean field near Roselawn, Indiana, killing all 64 passengers and 4 crew on board.

The National Transportation Safety Board (NTSB) stated that the probable cause of this crash was the flight into known icing conditions, with the aircraft being operated outside its "icing certification envelope". While the ATR's deicing boots were able to remove ice along the leading edge, it rapidly re-formed behind the boots as runback ice, where it could not be removed. This separated the airflow from the wing's surface and made the aileron control inadequate or non-existent. The ATR family of aircraft has had a history of known and reported control problems in icing conditions. For that reason, the NTSB also mentioned as contributing factors the "inadequate response" on part of the manufacturer and the French DGAC and United States' Federal Aviation Administration aviation authorities to these reports.

In the years following this accident, AMR Corporation stopped using its American Eagle ATRs out of their northern hubs and moved them to their southern and Caribbean hubs in Dallas, Texas; Miami, Florida and San Juan, Puerto Rico to alleviate potential icing problems in the future. Other U.S. ATR operators, particularly the SkyWest, Inc. subsidiary and Delta Connection operator Atlantic Southeast Airlines, continue to operate ATR-72 aircraft in areas where icing conditions are not common.

ATR issued modifications in its aircraft introducing extended de-icer boots and creating new procedures when encountering icing conditions. However, further incidents seem to indicate that there is no definitive solution for this problem in ATR aircraft.

This crash was featured on the Discovery Channel program The New Detectives.

• Aviation Safety Network summary
• NTSB AAR-96/01 – detailed Aircraft Accident ReportPDF (3.58 MiB), 340 pages)
• NTSB AAR-96/02 – comments of Bureau Enquète-AccidentsPDF (4.42 MiB), 341 pages)
• PlaneCrashInfo.Com entry on Flight 4184
• Tv.Com - New Detectives: Witness to Terror (Details Flight 4184 investigation)