The flight American Airlines 191 was crushed on May 25th, 1979, killing 271 people on board and 2 on the ground. This accident remains most fatal on the American ground. This flight, accomplished on a Douglas DC-10, connected the towns of Chicago and Los Angeles.

Plane

A DC-10-10, registered N110AA, serial number 46510, manufactured in February 1972 and propelled by 3 engines General Electric CF6-6D. The apparatus added up 19871 hours of flight at the time of the accident…

Crew

  • the commander : Walter Lux, 53 years, 22500 hours of flight including 3000 as a commander on DC-10.

  • the copilot : James Dillard, 49 years, 9275 hours of flight including 1080 on DC-10.
  • Engineer-mechanic : Alfred Udovich, 56 years, 15000 hours of flight including 750 on DC-10.
  • Personal of cabin : 10 people

Circumstances of the accident

May 25th, 1979, with 15:02 local time, the DC-10 springs for its takeoff since the track 32R de l' airport O' Hare of Chicago. Shortly after rotation the air-traffic controllers see the engine number 1 (left wing) to separate from the plane and to be crushed on the runway. The apparatus carries out a normal rise to approximately 350 feet whereas the Kérosène and the liquid of the hydraulic systems run out of the plane causing a perfectly visible trail. Such a problem is theoretically gérable and nonfatal since the displacement of the center of gravity and the modifications of the streamline flow remain within acceptable tolerances. The plane could have landed in full safety if the loss of the engine had not caused an other damage. Nevertheless, during the simulations carried out after the crash landing, only the pilots informed by advance of the problems of flight 191 could leave themselves business and avoid the crash landing. The pilots of flight 191, in accordance with the procedures in the event of engine failure, reduce speed to 159 nodes, but the pulling up of the engine considerably damaged the hydraulic systems which control the nozzles of leading edge wings - nozzles which make it possible to increase the Portance wings at the time of takeoffs and landings. Moreover, the missing engine made it possible to provide the power supply of the instruments, in particular the alarm of Décrochage, the indicators of exit of the nozzles and the vibrator of the handle only available for the commander. Contrary to the practice, the mechanical engineer had not engaged the feeding system of help. In other words the pilots could not be informed any more configuration of flight of the aircraft. Moreover it was impossible to see the engine since the Cockpit.

Progressively of the hydraulic loss of pressure, the nozzles of attack return, making pass the stalling speed of 124 nodes to 160 nodes. The plane losing speed, the left wing takes down whereas the right wing preserves bearing pressure. This imbalance then actuates the plane in a gimlet on the left unverifiable. It is crushed on a waste ground with 15:04, after 31 seconds of flight, 1400 meters in the North-West of the track. The plane disintegrates instantaneously, killing on the blow the 271 people on board. The explosion was so violent that the flames and the plume of smoke were visible until Chicago. Remains were projected on a carpark of mobil-homes, killing two people and by wounding two others seriously.

The Control tower tried well to contact the cockpit after having seen the engine falling but the crew never answered, undoubtedly too occupied trying to control the plane.

Assessment

  • Surviving: no
  • Dead: 258 passengers, 13 team members, 2 people on the ground.
  • the apparatus is destroyed with the impact.

Inquire

The result of the survey carried out by the National Transportation Safety Board (NTSB) was published on December 21st, 1979. It reveals that the accident is due to a caused damage with Tulsa during the disassembling of the pylon-engine unit. It is the pylon which was damaged following a bad operation. The normal procedure envisaged the disassembling of the engine before the disassembling of the pylon. To earn time and money American Airlines had asked its mechanics to dismount the engine and the pylon at the same time. A large lifting truck was used to support the engine while the pylon of the wing was taken down. It is during this operation carried out on DC-10 N110AA that an incident took place. The lifting truck had been left without monitoring following the shift. With the recovery, the carriage pushed the engine because of a problem of hydraulics. The exerted pressure was sufficient to create a broad indentation and a large fracture in the body of the pylon. Nobody noticed the fracture and it was accentuated flights progressively. At the time of the takeoff of the flight the 191 aerodynamic loads were sufficient to tear off the pylon of the wing completely. The loss of the engine, combined with the position raised of the lifting nozzles, could only involve one disaster. The NTSB concludes that being given the circumstances, the pilots cannot be blamed. The decision to continue takeoff was in conformity with the procedures and logic taking into account the speed of the plane at the time of the loss of the engine and information available in the cockpit.

The board of inquiry also blamed the bad design of the points of anchoring of the pylon and was astonished that McDonnell-Douglas, originator of the plane, never carried out tests aiming at studying the effects of the physical loss of an engine and its pylon knowing that, theoretically, this situation was controllable by the pilots from an aerodynamic point of view. Such a study would undoubtedly have made it possible to highlight structural weaknesses.

Chef-mécanicien who had carried out the operations of lifting committed suicide a few hours before testifying before the board of inquiry.

External bonds

  • Report/ratio of NTSB (pdf)

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