American Eagle Flight 4184 – Aircrash investigation

On 31 October 1994, Indianapolis International Airport, Indiana, USA, American Eagle Flight 4184 was on its scheduled domestic passenger flight to Chicago, Illinois, United States. The aircraft was operated by Simmons Airlines on behalf of American Eagle. There were 64 passengers and four crew members on board the flight.

Flight captain Orlando Aguilar, 29. He had been a professional pilot with an experience of around 8,000 hours, in which 1,548 hours on the ATR aircraft. Coworkers characterized Aguilar’s flying skills favorably and reflected mostly on the pleasant setting he created in the cockpit. The first officer was 30-year-old Jeffrey Gagliano. His friends also thought of him as a capable pilot. He had completed upwards of 5,000 hours of flight time, 3,657 of those were in the ATR plane.

Before departure, the flight crew received a company prepared, combined flight plan release, and weather package. The meteorological information provided to the crew did not contain Airman’s Meteorological Information (AIRMET) or any information regarding a weather forecast. AIRMETs are available to dispatchers for review and can be included in the flight release. AIRMETs are also available for the pilots to review at the departure station. There was no evidence to indicate whether the flight crew of flight 4184 had obtained this information.

Flight 4184 was expected to take off at 14:10 from Indianapolis, and land at 15:15 to O’Hare.

14:14

The aircraft was ready for departure and was left on the airport for 42 minutes until Illinois obtained an IFR clearance because the climate in Illinois began quickly changing.

14:53

ATC “… expect a little bit of holding in the air, and can start them up(engines) contact the tower when you are ready to go.”

Here, the controller did not specify to the crew the reason for either the ground or airborne hold.

14:55

In its 45 minutes trip to O’Hare International Airport, Chicago, Illinois, ATC approved American Eagle Flight 4184 for departure. The first officer carried over the flight pilot’s responsibilities.

The pilots enabled the autopilot as the aircraft continued for 1,800 feet.

15:11

The aircraft leveled at an altitude of 16,300 ft and was maintaining an airspeed of approximately 190 knots.

Captain with BOONE controller, “… we get a choice out with one zero thousand forty southeasts of its Levels we ‘re making our way to the ground now, checking through at one six thousand.”

The controller accepted the radio signal, and then when the aircraft deicing mechanism activated, Flight 4184 started the plunge to 10,000 feet.

The O’Hare arrival controller has instructed the BOONE sector to give holding orders to certain aircraft who were awaiting O’Hare.

15:18

Flight 4184 maintained at 10,000 feet. The BOONE controller has ordered the captain to remain in a holding position as directed by O’Hare arrival controller.

The captain got permission in the holding pattern of ten nautical mile legs, a velocity drop, and assurance of right spins while maintaining the level.

Captain “holding”

Staff switched the deicing system off.

Captain, “hey, in such turns whatever thing gets a high angle on the deck … we ‘re all reveling throughout the air just now.”

The angle of attach at that moment was 5 degree.

On the CVR, the following conversation and sounds monitored while the investigation

First Officer “Do we need flaps 15”? “

Captain, “I ‘m going to be probably shortly ready for the stall procedure now.”

Captain “would you like to knock them in (it’ll) bring the nose down.”

First Officer, “sure.”

The Angle Of Attack aircraft diminished to about 0 degrees as first officer applied 15 degrees of flaps.

Captain…” the trim, automatic trim.”

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At 15:41

The crew switched on a deicing mechanism for the aircraft and raised the rpm of the propeller around 77 to 86 percent. The aircraft was on a holding pattern throughout the third circle.

Captain “I am showing some ice now.”

Captain “I truly believe we can get the Overspeed until they let us out of hold and forget they ‘re down [flaps].”

At 15:44,

The commander left the cockpit and headed to the aircraft’s posterior section to use the toilet. Once he arrived to the cockpit, he called for a status report on ATC communications from the first officer. There’s no direct question into the state of the icing situations or the anti-icing devices on the aircraft.

First officer, “we ‘re already having ice.”

The captain did not acknowledge the statement orally.

BOONE Controller “descend and maintain eight thousand [feet].”

BOONE Controller “is expected to be about 10 minutes until you’re cleared in.”

The first officer, “thank you.”

15:56

The aircraft started to decline at 10,000 feet, the power factor was lowered to the idle position of the aircraft, the velocity of the propeller became 86 per cent, and autopilot stayed employed in the vertical speed. The flap Overspeed alert activated as the aircraft was dropping at 186 kts in such a 15 ° RWD attitude.

“I thought we’d go there,” Captain

The first officer, “I attempted to maintain it at around one-eighty.”

They lowered the flaps around 15 degrees to 0 degrees. The Angle of Attack (AOA) and pitching attitude improved as the flaps began heading to the zero degree position. The AOA rose by 5 degrees as the aircraft descended to 9,130 feet, and the ailerons quickly deteriorated to 13,43 degrees RWD. The autopilot immediately detached, and the aircraft quickly turned to the right, and the pitch attitude and AOA started to degrade.

The AOA reduced by 3.5 degrees within the few seconds of the preliminary aileron and roll excursion, the ailerons shifted to an almost neutral place, and the aircraft started rolling at 77 degree RWD.

The aircraft therefore started turning left, the elevator began to shift in a nose-up direction, the AOA continued to climb, and the pitch attitude ceased at about 15 degrees nose-down.

The nose-up row intensity of the captain surpassed 22 pounds, and the aircraft quickly rotated to the right at a pace of over 50 degrees per second.

Captain “all right man”

The altitude decreased through 4,900 feet.

Captain “sweet and simple.”

The aircraft hited a partly flattened damp soybean area in a nose-down with a low left-wing approach. The last data collected on the FDR appeared at an altitude of 1,682 feet with such a vertical speed of 500 feet per second, and reported airspeed of 375 knots, a nose-down pitched attitude of 38 degrees with a nose-up elevator of 5 degrees.

The aircraft was destroyed by force of impact. Nobody has survived that crash.

American Eagle Flight 4184
Crash site of American Eagle Flight 4184; photo by (Tom Strattman/AP)

Investigation

The United States National Transportation Safety Board ( NTSB) initiated the inquiry. They decided that the possible causes of the American Eagle Flight 4184 crash were control loss, due to a rapid and abrupt reversal of the aileron hinge moment. This was because an ice ridge agglomerated above the deice boots.

The NTSB accused manufacturer ATR, France’s aviation governing agency, and the FAA.

According to NTSB, under icing weather, ATR refused to properly report its planes’ control problems. The French regulatory agency has also refused to take the requisite appropriate measures to ensure the airworthiness of ATR aircraft under icing conditions. The FAA has neglected to adequately verify the airworthiness of ATR aircraft and change the criteria for aircraft registration to represent frozen rain situations.