How a missing bolt caused the crash of TWA flight 529.
TWA Flight 529 was a regularly scheduled passengers flight from Boston Logan International Airport (BOS) and San Francisco International Airport (SFO) with stops in New York, Pittsburgh, Chicago, Las Vegas, and Los Angeles.
The aircraft involved in what would be, at the time, the deadliest plane crash in American aviation history was a 16-year-old Lockheed L-049 Constellation with the registration N86511.
On Friday, September 1, precisely 61 years ago today, TWA Flight 529 was at Chicago Midway International Airport (MDW) for a crew change and refueling for its next leg of the journey to Las Vegas. The aircraft departed Midway at 02:00 from Runway 22L, heading westward at 5,000 feet.
A bolt had worked itself loose during the takeoff in the elevator boost system. Suddenly the plane pitched upwards and stalled. Unable to control the aircraft elevators, the plane crashed in a field near Hinsdale, DuPage County, Illinois killing all 78 passengers and crew.
Civil Aeronautics Board (CAB) immediately took over the crash investigation and pieced together the plane's wreckage. During the reassembly, it became apparent that a critical 5/16 inch bolt was missing from the plane's elevator boost linkage mechanism.
Unable to find the bolt at the crash site, investigators determined that it must have gone missing before the plane hit the ground. Without the bolt, when the aircraft elevators were in boost mode, it would make the plane uncontrollable.
The Lockheed Constellation L-049 was designed to allow the pilots to disable the hydraulic elevator boost and manually operate the elevators via a linkage system. The pilots of the doomed plane tried to disable the hydraulic boost as the aircraft pitched upwards, now pushing the control sticks forward to recover from the stall; the continuous downward pressure on the elevators made it impossible to revert to manual control. According to the CAB report, the pilots were not helping themselves gain manual control of the elevators by applying nose downward pressure.
In its final report released on December 18, 1962, the CAB concluded that the probable cause of the accident was the missing bolt from the elevator boost linkage system.
As a result of the CAB investigation, the Federal Aviation Administration (FAA) was advised to mandate a design change to the elevator boost control. The request was for aircraft manufacturers to design a system that could easily be reverted to manual operation even during downward pressure.
Despite the deadly crash and the FAA knowing what caused it, they did not call on planemakers to redesign the system but instead to incorporate procedural changes in the aircraft's flight manual.
To mark the 60th anniversary of the crash, on September 1, 2021, a special memorial service was held at Prairie Trail Park in Willowbrook, Illinois. During the memorial service, a plaque was unveiled in honor of the victims and first responders. Today the crash site is underdeveloped woodland surrounded by houses.
Journalist – Mark is an experienced travel journalist having published work in the industry for more than seven years. His enthusiasm for aviation news and wealth of experience lends itself to some excellent insight, with his work cited in Forbes amongst other publications. Based in Alicante, Spain.
TWA Flight 529: Formerly The US's Deadliest Single-Aircraft Accident – Simple Flying
