New algorithm could help prevent midair collisions

The Federal Aviation Administration (FAA) has mandated that by 2020, all commercial aircraft - and small aircraft flying near most airports - must be equipped with a new tracking system that broadcasts GPS data, providing more accurate location information than ground-based radar.

In anticipation of the deadline, the FAA has also charged MIT researchers with leading an investigation of the system's limits and capacities.

In October, at the 30th Digital Avionics Systems Conference in Seattle, MIT researchers will present an early result of that investigation, a new algorithm that uses data from the tracking system to predict and prevent collisions between small aircraft. In the last 10 years alone, 112 small planes have been involved in midair collisions, and thousands more have reported close calls.

The chief challenge in designing a collision-detection algorithm, says Maxime Gariel, a postdoc in MIT's International Center for Air Transportation and lead author on the new paper, is limiting false alarms.

''If half the time it's a false alert,'' Gariel says, ''[people] are not going to listen to it, or they'll turn it off.'' At the same time, the algorithm has to have some room for error:

While GPS is more accurate than radar tracking, it's not perfect; nor are the communications channels that planes would use to exchange location information. Moreover, any prediction of a plane's future position can be thrown off by unexpected changes of trajectory.