Software Failure: Air Traffic Control System

Presented by: S.A Arain & A.R Shaikh

Dated: 10-11-2009

Mehran University Institute of Science and Technology Development

Overview

• Introduction

• Los Angeles Air Control System

• What went Wrong?

• Causes of this Software Failure

• Conclusions

Air Control System, Software Failure

Mehran University Institute of Science and Technology Development

IntroductionThis event was the worst nightmare in the Air control system’s history, on Tuesday, 24th September 2007, Los Angeles Air Controllers lost voice contact with 400 hundred airplanes flying in range. The reason was the unexpected Shutdown of the main Controlling System and then the failure of Backup system to take over, that was supposed to take over within 60 seconds of the main controller's failure.

Air Control System, Software Failure

Mehran University Institute of Science and Technology Development

Los Angeles Air Control System This Air Control System was developed by

Harris Corp., Melbourne, Florida working since 1990.

The name given to this Voice Switching and Control System (VSCS) was Palmdale.

In the world, 21 Palmdale systems are implemented and are still working.

VSCS was a very complex system and was connecting 160 air traffic controller positions

Air Control System, Software Failure

Mehran University Institute of Science and Technology Development

What Went Wrong?

In a statement issued the next day, the FAA laid the blame squarely on human error:

"Our preliminary findings indicate that the outage was not the result of system reliability but rather an event that should've been avoided had strict FAA operating and maintenance procedures been followed."

Air Control System, Software Failure

Mehran University Institute of Science and Technology Development

What Went Wrong?

But actually that was more then a Human error. In the user manual it was instructed to restart the system every month but that was the technical glitch in this software.

Inside the control system unit is a countdown timer that ticks off time in milliseconds. The VCSU uses the timer as a pulse to send out periodic queries to different sub systems to operate properly.

Air Control System, Software Failure

Mehran University Institute of Science and Technology Development

What Went Wrong?

It starts out at the highest possible number that the system's server and its software can handle--232. It's a number just over 4 billion milliseconds. When the counter reaches zero, the system runs out of ticks in almost 50 days and can no longer time itself. So it shuts down.

Air Control System, Software Failure

Mehran University Institute of Science and Technology Development

Causes of this Software Failure

This timing issue was an oversight, Harris, the manufacturer, was aware of the problem but didn't really know how it would impact the system.

It was insane for the FAA to continue to operate a system with a known problem. And by doing that, they expose themselves to this failure.

Air Control System, Software Failure

Mehran University Institute of Science and Technology Development

Conclusions The case is self explanatory, the issues that

made this complex project a partially abundant software project could be categorized as: Technical deficiencies Unenthused and passive client participation

If proper collaborated efforts might have been taken in the development, testing and implementation phases, that incident of software failure might have been avoided.

Air Control System, Software Failure

Mehran University Institute of Science and Technology Development