Hazardous Ice

On Oct. 31, 1994, an ATR 72, American Eagle Flight 4184, departed from Indianapolis for Chicago O’Hare International Airport with 64 passengers and four crewmembers. Due to traffic at O’Hare, the aircraft was held over Roselawn, Indiana, at 10,000 ft in icing conditions. The ice protection system (IPS) was functioning, and the wing flaps were partially extended. Air traffic control cleared the aircraft to 8,000 ft, and while descending, the flap overspeed warning sounded. The copilot raised the wing flaps, and the angle of attack began increasing. Suddenly, the right wing stalled, the autopilot disconnected, and the control column deflected full right. The aircraft rolled uncontrollably into a steep right bank and entered a dive. As the angle of attack decreased in the dive, aileron control was regained, but both pilots began pulling back on the control column to recover from the dive. Angle of attack increased, the right wing stalled a second time, and the control column again def…