The focus of my project is going to be on a particular accident that took place on July 19, 1989 when a McDonnell Douglas DC-10-10 (Ref fig 1) aircraft crashed in Sioux City, Iowa. Not only the accident and why it happened but to delve into the root cause of the accident, the failure of the number two engine and why it happened. This particular type of aircraft, at the time of the accident, had been in production for about 18 years. The United Airlines jet was bound for Chicago when the ta

On July 19,1989 a United Airlines DC-10-10 passenger plane took off Stapleton International Airport in Denver Colorado. The plane was scheduled to make a quick stop in Chicago, Illinois and then continue on to Philadelphia, PA. After an uneventful hour of flight a loud thump was heard, followed by a violent shaking of the aircraft. The flight crew observed the tail-mounted engine was not operating. While performing an engine shutdown procedure, the crew noticed that the fuel lever wouldn’t move to the closed position. They also observed that the hydraulic fluid quantities were all at zero. When the co-pilot tried to maneuver airplane it confirmed the loss of fluid when the airplane did not respond to his commands. The crew then radioed to the air traffic controller that they needed emergency assistance to the nearest airport. Sioux City Iowa was found to be the almost straight-ahead so it was chosen. After the captain briefed the passengers of the up-coming trials, a United Airlines DC-10 pilot instructor asked if he could be of any assistance. The captain asked him to see if there was any damage that he could see. The instructor found that the flight controls on the wings weren’t moving and that the horizontal stabilizer had damage to the left and right side. The horizontal stabilizer is the part of the aircraft that controls elevation and what is known as yaw. (Right and left turning) Without hydraulics the crew was limited on how to control the aircraft so the instructor pilot recommended the use of engine power to maneuver the airplane. The idea appeared to work when tried and being that all other options were few, the crew adopted this plan of action.

There are many variants of NDT but a process that is known as Florescent Penatrant Inspection is commonly used on LLP’s. (Life limited Parts) The part is dispensed in a florescent fluid and then placed under a ultra-violet light. If a surface or sub surface crack exists, it would be visible. Much of the effort in NDT has gone towards identifying when and where cracks have developed in rotating hardware. In a jet engine, rotating parts are inspected at regular intervals. Another form of NDT crack detection is a process known as eddy current testing. Eddy current testing is a better (safer) process than FPI due to the fact that eddy current can protrude through the entire part unlike FPI which can only do the surface and sub-surface testing. The major drawback to eddy current testing is the testing equipment can only be for a specific or localized area unlike FPI, which doesn’t require special testing equipment.

The National Transportation and Safety Board (NTSB) now needed to understand why the accident occurred. Since the tail section was the potential cause of the crash, they transported the tail section parts to a nearby hangar and began to reconstruction of the tail. Once the tail section was completed this puzzle was starting to piece together. The left side of the horizontal stabilizer showed no damage that could have cause the crash. (See figure 2-3) However, the right side was a different story. The right side of the stabilizer indicated that approximately seventy pieces of metal had pierced through the skin. When aircraft engines are designed, the design engineers know they must be able to contain a sizable failure. The CF6-50 has what is called a containment case. (Ref figure 4) Like its name, is designed to contain an engine during failure. However, the engine involved in the Sioux City crash exceeded its design capabilities. When the tail mounted engine failed, metal debris violated the containment case and destroyed the number two hydraulic system line

Some topics in this essay:
Airlines DC-10, McDonnell Douglas, Hard Alpha, Alta Iowa, LLP’s Life, United Airlines, Board NTSB, Sioux City, NDT NDT, GE CF6-6, fan disk, united airlines, hydraulic system, eddy current, ref figure, mcdonnell douglas, eddy current testing, uncontained failures, tail section, sioux city, horizontal stabilizer, air traffic controller, stage 1 fan, 1 fan disk, transportation safety board,