American Eagle Flight 4184 was a commuter flight that fatally crashed after loss of control due to icing conditions.

N401AM, an ATR 72 (72-212) aircraft, was operated by Simmons Airlines on behalf of American Eagle, a subsidiary of American Airlines.

On October 31, 1994, Flight forty-one eighty-four was en route from Indianapolis International Airport, Indiana to O'Hare International Airport, Chicago, Illinois.

Due to bad weather conditions at the destination, which resulted in delays, the crew was advised by ATC to hold at the nearby LUCIT intersection at 10,000 ft. In this area they encountered heavy icing conditions known as freezing rain (supercooled droplets, which cause intense ice buildup on the aircraft structure within very little time). Shortly later, they were cleared down 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, while the crew was unable to gain back 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 NTSB stated as probable cause of this crash the flight into known icing conditions, with the aircraft being operated outside its "icing certification envelope". This type of aircraft has had a long 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 US (FAA) aviation authorities to these reports.

The ATRs have had this design problem from the very beginning: their wings have inflatable rubber de-icing boots, which (in other types of aircraft as well) are unable to cope with the rapid ice aggregation during flight through freezing rain.

Dramatization

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

External links

• Aviation Safety Network (short summary of accident report)
• NTSB (AAR-96/01 – detailed Aircraft Accident Report, *.pdf, 340 pages)
• NTSB (AAR-96/02 – comments of Bureau Enquète-Accidents, *.pdf, 341 pages)