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On May 25, 1979, American Airlines Flight 191 crashed on takeoff.
Sat May 25, 2019: 40 Years Ago Today; American Airlines Flight 191
Sat May 25, 2019: Forty years ago today, American Airlines Flight 191 crashed on takeoff
I remember this one.
American Airlines Flight 191
Flight 191 just after takeoff and before hitting the ground, with its left engine missing and leaking hydraulic fluid.
Date: May 25, 1979
Summary: Loss of control caused by engine detachment due to improper maintenance
Site: Des Plaines, Illinois, United States (Near O'Hare International Airport) 42°0?35?N 87°55?45?W
Total fatalities: 273
Aircraft type: McDonnell Douglas DC-10-10
American Airlines Flight 191 was a regularly scheduled passenger flight operated by American Airlines from O'Hare International Airport in Chicago, Illinois, to Los Angeles International Airport in Los Angeles, California. On May 25, 1979, the McDonnell Douglas DC-10-10 operating this flight was taking off from runway 32R when it crashed into the ground. All 258 passengers and 13 crew on board were killed, along with two people on the ground. With 273 fatalities, it is the deadliest aviation accident to have occurred in the United States.
The National Transportation Safety Board (NTSB) found that as the aircraft was beginning its takeoff rotation, engine number one (the left engine) separated from the left wing, flipping over the top of the wing and landing on the runway. As the engine separated from the aircraft, it severed hydraulic fluid lines that locked the wing's leading-edge slats in place and damaged a 3 feet (1 m) section of the left wing's leading edge. Aerodynamic forces acting on the wing resulted in an uncommanded retraction of the outboard slats. As the aircraft began to climb, the damaged left wing – with no engine – produced far less lift (stalled) than the right wing, with its slats still deployed and its engine providing full takeoff thrust. The disrupted and unbalanced aerodynamics of the aircraft caused it to roll abruptly to the left until it was partially inverted, reaching a bank angle of 112 degrees, before crashing in an open field by a trailer park near the end of the runway. The engine separation was attributed to damage to the pylon structure holding the engine to the wing, caused by improper maintenance procedures used at American Airlines.
{snip}
Engine separation
{snip}
The NTSB determined that the damage to the left wing engine pylon had occurred during an earlier engine change at the American Airlines aircraft maintenance facility in Tulsa, Oklahoma, between March 29 and 30, 1979. On those dates, the aircraft had undergone routine service, during which the engine and pylon had been removed from the wing for inspection and maintenance. The removal procedure recommended by McDonnell-Douglas called for the engine to be detached from the pylon before detaching the pylon itself from the wing. However, American Airlines, as well as Continental Airlines and United Airlines, had developed a different procedure that saved approximately 200-man-hours per aircraft and "more importantly from a safety standpoint, it would reduce the number of disconnects (of systems such as hydraulic and fuel lines, electrical cables, and wiring) from 79 to 27." This new procedure involved the removal of the engine and pylon assembly as a single unit, rather than as individual components. United Airlines' implementation involved the use of an overhead crane to support the engine/pylon assembly during removal and installation. The method chosen by American and Continental's procedures supported the engine/pylon assembly with the hold of a large forklift.
It was learned that if the forklift was incorrectly positioned, the engine/pylon assembly would not be stable as it was being handled, causing it to rock like a see-saw and jam the pylon against the wing's attachment points. Forklift operators were guided only by hand and voice signals as they could not directly see the juncture between pylon and wing. Positioning had to be extremely accurate or structural damage could result. Compounding the problem, maintenance work on N110AA did not go smoothly. The mechanics started to disconnect the engine and pylon, but there was a shift change halfway through the job. When work was resumed, the pylon was jammed on the wing and the forklift had to be re-positioned, resulting in unseen structural damage to the wing's pylon attachment points. The structural damage was not enough to cause an immediate failure. However, the damage to the mount developed into fatigue cracking, and worsened with each takeoff and landing cycle during the eight weeks that followed the maintenance on N110AA. Finally, the damaged rear pylon mount was weakened to such an extent that it was no longer able to support even normal flight loads, and failed. Due to the absence of this attachment, at full takeoff power the engine and its pylon fell off the wing. The structure surrounding the forward pylon mount then failed from the resulting stresses.
Inspection of the DC-10 fleets of the three airlines revealed that while United Airlines' hoist approach seemed to be harmless, there were several DC-10s at both American and Continental that already had fatal damage to their pylon mounts. The field service representative from McDonnell-Douglas stated the company would "not encourage this procedure due to the element of risk" and had so advised American Airlines. McDonnell-Douglas, however, "does not have the authority to either approve or disapprove the maintenance procedures of its customers."
{snip}
Flight 191 just after takeoff and before hitting the ground, with its left engine missing and leaking hydraulic fluid.
Date: May 25, 1979
Summary: Loss of control caused by engine detachment due to improper maintenance
Site: Des Plaines, Illinois, United States (Near O'Hare International Airport) 42°0?35?N 87°55?45?W
Total fatalities: 273
Aircraft type: McDonnell Douglas DC-10-10
American Airlines Flight 191 was a regularly scheduled passenger flight operated by American Airlines from O'Hare International Airport in Chicago, Illinois, to Los Angeles International Airport in Los Angeles, California. On May 25, 1979, the McDonnell Douglas DC-10-10 operating this flight was taking off from runway 32R when it crashed into the ground. All 258 passengers and 13 crew on board were killed, along with two people on the ground. With 273 fatalities, it is the deadliest aviation accident to have occurred in the United States.
The National Transportation Safety Board (NTSB) found that as the aircraft was beginning its takeoff rotation, engine number one (the left engine) separated from the left wing, flipping over the top of the wing and landing on the runway. As the engine separated from the aircraft, it severed hydraulic fluid lines that locked the wing's leading-edge slats in place and damaged a 3 feet (1 m) section of the left wing's leading edge. Aerodynamic forces acting on the wing resulted in an uncommanded retraction of the outboard slats. As the aircraft began to climb, the damaged left wing – with no engine – produced far less lift (stalled) than the right wing, with its slats still deployed and its engine providing full takeoff thrust. The disrupted and unbalanced aerodynamics of the aircraft caused it to roll abruptly to the left until it was partially inverted, reaching a bank angle of 112 degrees, before crashing in an open field by a trailer park near the end of the runway. The engine separation was attributed to damage to the pylon structure holding the engine to the wing, caused by improper maintenance procedures used at American Airlines.
{snip}
Engine separation
{snip}
The NTSB determined that the damage to the left wing engine pylon had occurred during an earlier engine change at the American Airlines aircraft maintenance facility in Tulsa, Oklahoma, between March 29 and 30, 1979. On those dates, the aircraft had undergone routine service, during which the engine and pylon had been removed from the wing for inspection and maintenance. The removal procedure recommended by McDonnell-Douglas called for the engine to be detached from the pylon before detaching the pylon itself from the wing. However, American Airlines, as well as Continental Airlines and United Airlines, had developed a different procedure that saved approximately 200-man-hours per aircraft and "more importantly from a safety standpoint, it would reduce the number of disconnects (of systems such as hydraulic and fuel lines, electrical cables, and wiring) from 79 to 27." This new procedure involved the removal of the engine and pylon assembly as a single unit, rather than as individual components. United Airlines' implementation involved the use of an overhead crane to support the engine/pylon assembly during removal and installation. The method chosen by American and Continental's procedures supported the engine/pylon assembly with the hold of a large forklift.
It was learned that if the forklift was incorrectly positioned, the engine/pylon assembly would not be stable as it was being handled, causing it to rock like a see-saw and jam the pylon against the wing's attachment points. Forklift operators were guided only by hand and voice signals as they could not directly see the juncture between pylon and wing. Positioning had to be extremely accurate or structural damage could result. Compounding the problem, maintenance work on N110AA did not go smoothly. The mechanics started to disconnect the engine and pylon, but there was a shift change halfway through the job. When work was resumed, the pylon was jammed on the wing and the forklift had to be re-positioned, resulting in unseen structural damage to the wing's pylon attachment points. The structural damage was not enough to cause an immediate failure. However, the damage to the mount developed into fatigue cracking, and worsened with each takeoff and landing cycle during the eight weeks that followed the maintenance on N110AA. Finally, the damaged rear pylon mount was weakened to such an extent that it was no longer able to support even normal flight loads, and failed. Due to the absence of this attachment, at full takeoff power the engine and its pylon fell off the wing. The structure surrounding the forward pylon mount then failed from the resulting stresses.
Inspection of the DC-10 fleets of the three airlines revealed that while United Airlines' hoist approach seemed to be harmless, there were several DC-10s at both American and Continental that already had fatal damage to their pylon mounts. The field service representative from McDonnell-Douglas stated the company would "not encourage this procedure due to the element of risk" and had so advised American Airlines. McDonnell-Douglas, however, "does not have the authority to either approve or disapprove the maintenance procedures of its customers."
{snip}
2 replies
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