NACE Resource Center
|Corrosion - Aircraft|
EL AL Boeing 747 Crash
On October 4, 1992 an EL AL 747 freighter crashed in Amsterdam, killing all four people on board and over 50 people on the ground. The cause of the crash was the number 3 and 4 engines separated from the wing, causing a loss of control.
The reason for the number 3 engine separation was a breakage of the fuse pin. The pin was designed to break when an engine seizes in flight, producing a large amount of torque. Both of the engines were stripped off the right wing causing the Boeing 747-200 Freighter to crash as it maneuvered towards the airport.
Unfortunately this was not the first Boeing 747 to crash in this way. In December 1991 a China Airlines Boeing 747-200F freighter crashed shortly after takeoff. A possible reason for the shearing away of the two right engines is that corrosion pits and fatigue weakened the fuse pins that hold the strut to the wings. Pits cause a breakdown in the structural integrity and their formation and growth rate is unpredictable. These pits usually form via a lack of passivity, surface discontinuities, or insufficient inhibitor coverage. Fatigue also weakens structures; in this case, by the cyclic loading and unloading of pressure brought on by the day to day routine of a plane. Constant pressure variance coupled with the corrosion may cause the pits to expand into a 14 inch crack such as the one found in one of the fuse pins from the El Al 747.
In both the El Al crash and the China Airlines crash the No.3 and No.4 engines on the right side of the plane ripped away from the fuselage. It is believed that in the El Al crash the inboard fuse pin failed due to corrosion cracking and fatigue which caused the outboard fuse pin, already weakened by a crack, to fail. With these two pins malfunctioning the No.3 engine tore off the plane in such a way that it may have taken the No.4 engine with it. Boeing had just begun distributing a safety bulletin pertaining to the inspection of all fuse pins on their 747- 100/200/300 that used Pratt & Whitney and Rolls-Royce engines. Both the El Al and China Airlines planes were Boeing 747-200 s with Pratt & Whitney engines. This design of the fuse pin has been used since 1982 and in a seven year period there have been fifteen reports of cracked pins. It was discovered that these pin failures resulted from the absence of primer, cadmium plating, and a corrosion preventative.
Since the El Al 747 crash, Boeing has begun designs to upgrade the 747. Specific targets on this model include fabricating new parts for the pylon-to-wing attachment for the Pratt & Whitney engines. Boeing also has plans to make inspecting the planes as cost and time efficient as possible.
See also on the subject of stress corrosion cracking:
Basics of SCC, Causes of SCC, Controlling SCC, EL AL crash, Environments & SCC, Pipeline SCC, SCC definition, SCC of aircraft component, SCC Mechanism, Swiss roof collapse, Testing strategy, Williams explosions
Other catastrophic corrosion accidents:
Aloha incident, Bhopal accident, Bogalusa explosion, Carlsbad explosion, Guadalajara explosion, EL AL crash, F-16 aircraft, Davis-Besse, Mihama-3, Oil pipelines, Silver bridge, The Erika, Flixborough explosion, Swiss Roof Collapse