By Kim Smiley
Hundreds of flights were disrupted in the Los Angeles area on April 30, 2014 when the air traffic control system En Route Automation Modernization system, known as ERAM, crashed. It’s been reported that the presence of a U-2 spy plane played a role in the air traffic control issues.
This issue can be analyzed by building a Cause Map, a visual format for performing a root cause analysis. A Cause Map intuitively lays out the cause-and-effect relationships so that the problem can be better understood and a wider range of solutions considered. In order to build a Cause Map, the impacted goals are determined and “why” questions are asked to determine all the causes that contributed to the issue.
In this example, the schedule goal was clearly impacted because 50 flights were canceled and more than 400 were delayed. Why did this occur? The flight schedule was disrupted because planes were unable to land or depart safely because the air traffic control system used to monitor the landings was down. The computer system crashed because it became overwhelmed when it tried to reroute a large number of flights in a short period of time.
The system attempted to reroute so many flights at once because the system’s calculations showed that there was a risk of plane collisions because the system misinterpreted the flight path, specifically the altitude, of a U-2 on a routine training mission in the area. U-2s are designed for ultra-high altitude reconnaissance, and the plane is reported to have been flying above 60,000 feet, well above any commercial flights. The system didn’t realize that the U-2 was thousands of feet above any other aircraft so it frantically worked to reroute planes so they wouldn’t be in unsafe proximity.
It took several hours to sort out the problem, but then the Federal Aviation Administration was able to implement a short term fix relatively quickly and get the ERAM system back online. The ERAM system is being evaluated to ensure that no other fixes are needed to ensure that a similar problem doesn’t occur again. It’s also worth noting that ERAM is a relatively new system (implementation began in 2002) that is replacing the obsolete 1970s-era hardware and software system that had been in place previously. Hopefully there won’t be many more growing pains with the changeover to a new air traffic control system.
To see a high level Cause Map of this problem, click on “Download PDF” above.