China Airlines Boeing 737 Flight 120
Kelvin Taylor
SFTY 335
Submitted: 12/4/2013

Abstract
This paper will give you an insight on what can go wrong when one missing washer caused an aircraft to be destroyed. There are many factors that could have led to that washer being missing, but all the factors can be broken down into four main categories. The first and often time the leading corporate is the human factor. The next category is initial and recurring training and certifications. The third category is maintenance practices. This category refers to the culture and practices of maintenance personnel. The last category is mechanical failure, which most times happened because of the human factor. As one begins to look at these four categories one can see how each one is connected to the other, making essentially a chain. When one of the chains links are broken most time it will led to some kind of failure, whether it be something minor or to something major.

China Airlines Boeing 737 Flight 120 What happened to China Airlines’ B737-800, tail number B18616? The plane departed from Taipei at 08:14 and arrived at Okinawa-Naha Airport (OKA) at 10:27. The plane then proceeded to taxi to its parking stall, once reaching the stall area flames began to come from underneath the plane the right engine tailpipe and right aft landing gear. Everyone was able to exit the plane, but the plane was destroyed. To explain how this could happen one can look at four main categories, Human factor, training and certifications, maintenance practices, and mechanical failure. The Human Factor accounts for most aviation incidents; it’s basically saying that a human being made a mistake that led to something going wrong. Now that mistake can be as simple as forgetting to close a circuit breaker or as big as not securing a panel. China Airlines flight 120 human factors’ can be explained in a chain of events that would eventually lead to an aircraft being destroyed. Back in December of 2005 Boeing issued a Service Letter (No. 737-SL-084), and it recommended that, “removal, inspection, and reinstallation of the bolt assembly, including application of thread locking compound, and tightening the nut with a torque of 50 to 80 inch-pounds” ("China Airlines Flight," 2007). The reason that Boeing released this Service Letter was because of,
The first reported track can puncture was on September 15, 2005. This fuel leak came from the wing leading edge area at the inboard end of the No. 5 leading edge slat. The hole created in this incident was small which caused a low rate fuel leak. This leak then dripped onto the engine exhaust nozzle, but did not cause a fuel fire. The incident was determined to be a result of loose hardware (a nut) falling into the track can and puncturing it during the slat's retraction. However, unlike China Airlines Flight 120, there had been no maintenance actions performed on the No. 5 slat can area that would have contributed to this incident ("China Airlines Flight," 2007).
Boeing also received a report of a second incident that cased the detachment of the nut on the downstop assembly in 2005. This inspection was to be done at the next convenient maintenance opportunity. However, the Service Letter did not indicate which slat track(s) to check. Boeing then released another Service Letter in March of 2006 (No. 737-SL-57-084-A). This letter did not make any changes to the description of the action, but another letter was released in July 10, 2007 (No. 737-SL-57-084-B) which completely removed the reference to the No.5 slat track. Someone over looking and not effectively communicating what should be inspected in the slat track(s); it started the first link of a chain of events that would lead to an aircraft incident. For aircraft B18616 that inspection would be done during a C Check, which is scheduled maintenance, from July 6 to 13, 2007. The slat track inspection was done on