Remembering American 191
Image Credit
45 years ago today, on May 25th, 1979, American Airlines Flight 191 crashed shortly after takeoff from Chicago’s O’hare International Airport, killing all 271 occupants and an additional 2 people on the ground. To date, the crash of AA 191 is the deadliest aviation accident (and third deadliest crash, after the aircraft that hit the Twin Towers) in American history.
What Happened?
Notice: I won’t go into any sort of graphic detail, but some may find this disturbing. So, consider yourself warned.
AA 191 was a regularly scheduled flight between Chicago - O’hare International Airport (ORD/KORD) and Los Angeles International Airport (LAX/KLAX). On May 25th, the DC-10 operating the flight was N110AA, which at the time was just over 7 years of age with 20,000 flying hours. The aircraft was powered by three General Electric CF6-6D engines. The crew of the day was highly experienced, with a combined 46,275 flight hours between the captain, first officer, and flight engineer.
At 3:04 PM local time, AA 191 was cleared for takeoff on 32R. During the takeoff roll, the number one engine and its pylon assembly (the one mounted on the left wing) completely separated from the wing, taking with it about 3 feet of leading edge surface. As they were beyond V1, the crew opted to continue the takeoff. The DC-10 is able to fly on just two engines. Unfortunately, it’s not exactly known what was said in the flight deck after this point, as the CVR (cockpit voice recorder) lost power or failed when the engine detached.
The crew appears to have followed the engine failure procedures, climbing out at 153 knots and a pitch of 14° to maintain said speed. The engine separation cut the hydraulic lines that operated the leading-edge slats on the left wing, locking them in position. As a result, the outboard slats just to the left of engine one retracted due to air pressure. The slat retraction increased the stall speed of the left wing to approximately 159 knots, which was 6 knots above the designated takeoff safety speed of 153 knots. This caused the left wing to enter a full aerodynamic stall.
With the left wing stalled, the aircraft began to bank left, eventually rolling onto its side.
The aircraft ultimately crashed into a field about 4,600 feet from the end of the runway. The force of the impact sent large pieces of debris into a nearby trailer park, destroying five trailers and several vehicles. The DC-10 also struck an old storage hangar on the edge of the airport, located at the former site of Ravenswood Airport. The aircraft was completely destroyed by the impact and the ignition of nearly 21,000 gallons of fuel. Everyone onboard was immediately killed, with an additional two deaths in a nearby repair shop in Des Plaines (a Chicago suburb). Two more were injured.
How’d This Happen?
Because of how busy an airport O'Hare is, there were scores of witnesses to help the investigators. There was an early agreement that nothing external had hit the aircraft during its takeoff roll to cause the engine to tear off. During the investigation, inspectors found damage to the wing’s pylon mounting bracket that matched the bent shape of the pylon’s rear attachment fitting. This indicated that the attachment fitting had impacted the mounting bracket at some point.
The NTSB found that the damage to the left-wing engine pylon had occurred during a prior engine change at American Airlines’ maintenance facility in Tulsa, Oklahoma two months prior to the crash. During that time, the aircraft underwent regular maintenance, which included removing the engine and pylon from the wing for inspection and maintenance. The aircraft manufactured recommended detaching the engine from the pylon before removing the pylon from the wing. However, American Airlines, along with Continental and United, had adopted an alternative procedure that saved approximately 200 labor hours per aircraft (and thus money). More importantly, from a safety perspective, it reduced the number of system disconnections (such as hydraulic lines, fuel lines, and electrical wiring). Less detachments = less things that could theoretically go wrong or be misplaced. This different method involved removing the engine and pylon together as a single unit rather than separately.
The NTSB believes that the engine pylon was incorrectly reinstalled, making it less stable. After the crash, both American and Continental found 3 other DC-10s that had fatigue cracking and bending damage from the exact same procedure.
A secondary contributing factor was believed to be asymmetrical drag from the damage to the leading edge slats, which caused inadequate speed on the climb.
A Quick Note
The sources I was reading through were quite technically complicated. I don’t have the best grasp on this sort of mechanical engineering lingo, and I didn’t want to just copy and paste verbatim from Wikipedia or something, so I did my very best to try and put it in my own words and preserve the integrity of the information. If something is wrong, or doesn’t seem quite right, please to let me know and I apologize in advance.
Victims & Legacy
This crash claimed 273 lives. Among the dead was Itzhak Bentov, a renowned biomedical engineer, and Leonard Stogel, a notable record producer. The vast majority of the victims were from the United States, but there were a few passengers from Saudi Arabia, South Korea, Belgium, Austria, and the Netherlands.
For thirty two years after the crash, there was no memorial at the crash site. In 2009, 6th graders at Decatur Classical School raised money to put up a memorial at Lake Opeka, just over a mile from the site of the accident. Because of how severe the crash and ensuing fire was, thirty people never were identified. They were buried in Rancho Palos Verdes, California, where there is a small monument to honor the nameless fatalities.
The crash’s impact stretched far beyond the families of the passengers and crew. The DC-10, once hailed as a marvel of modern aviation with cutting edge safety systems drew intense scrutiny from the government and public alike. There had been two crashes relating to the DC-10’s design flaws (American Airlines Flight 96 and Turkish Airlines Flight 981), and early speculation was that another design flaw had crashed AA191. The FAA grounded the DC-10 shortly after the crash, and while the aircraft was later cleared of any shoddy design, the public’s views of the plane were forever tainted.
American was fined $500,000 (equivalent to $1.6 million today) in response to the crash and the dangerous maintenance practices that led up to it.
Sources
National Transportation Safety Board Official Accident Report
Aviation Maintenance Magazine
Federal Aviation Administration “Lessons Learned”
Simple Flying
CBS News Chicago
.