On September 8, 2015, an airplane caught fire during take-off from an airport in Las Vegas, Nevada. The pilot was able to stop the plane, reportedly in just 9 seconds after becoming aware of the fire. The crew then evacuated the 157 passengers, 27 of whom received minor injuries as a result of the evacuation by slide. Although the National Transportation Safety Board (NTSB) investigation is ongoing, information that is known, as well as potential causes that are under consideration, can be diagrammed in a Cause Map, or visual root cause analysis.
The first step of Cause Mapping is to define the problem by completing a problem outline. The problem outline captures the background information (what, when and where) of the problem, as well as the impact to the goals. In this case, the safety goal is impacted due to the passenger injuries. The evacuation of the airplane impacts the customer service goal. The NTSB investigation impacts the regulatory goal. The schedule goal is impacted by a temporary delay of flights in the area, and the property goal is impacted by the significant damage to the plane. The rescue, response and investigation is an impact to the labor goal.
The Cause Map is built by beginning with one of the impacted goals and asking “Why” questions to develop the cause-and-effect relationships that led to an issue. In this case, the injuries were due to evacuation by slide (primarily abrasions, though some sources also said there were some injuries from smoke inhalation). These injuries were caused by the evacuation of the airplane. The airplane was evacuated due to an extensive fire. Another cause leading to the evacuation was that take-off was aborted.
The fact that take-off was able to be aborted, for which the pilot has been hailed as a hero, is actually a positive cause. Had the take-off been unable to be aborted, the result would likely have been far worse. In the case of the Concorde accident, a piece of debris on the runway ruptured a tire, which caused damage to the fuel tank, leading to a fire after the point where take-off could be aborted. Instead, the aircraft stalled and crashed into a hotel, killing all onboard the craft and 4 in the hotel. The pilot’s ability to quickly save the plane almost certainly saved many lives.
The fire is thought to have been initiated by an explosion in the left engine due a catastrophic uncontained explosion of the high-pressure compressor. This assessment is based on the compressor fragments that were found on the runway. This likely resulted from either a bird strike (as happened in the case of US Airways flight 1549), or a strike from other debris on the runway (as occurred with the Concorde), or fatigue failure of the engine components due to age. This is the first uncontained failure of this type of engine, so some consider fatigue failure to be less likely. (Reports of an airworthiness directive after cracks were detected in weld joints of compressors were in engines with different parts and a different compressor configuration.)
In this incident, the fire was unable to be put out without assistance from responding firefighters. This is potentially due to an ongoing leak of fuel if fuel lines were ruptured and the failure of the airplane’s fire suppression system, which reportedly deployed but did not extinguish the fire. Both the fuel lines and fire suppression system were likely damaged when the engine exploded. The engine’s outer casing is not strong enough to contain an engine explosion by design, based on the weight and cost of providing that strength.
The NTSB investigation is examining airplane parts and the flight data and cockpit voice recorders in order to provide a full accounting of what happened in the incident. Once these results are known, it will be determined whether this is considered an anomaly or whether changes to all planes using a similar design and configuration need to take action to prevent against a similar event recurring.
To view the initial investigation information on a one-page downloadable PDF, please click “Download PDF” above.