Sunday, February 11, 2007

Avoiding Midairs

I had a commenter ask how we in the airline world avoid midair collisions. Given the number of planes in the air at any given time, that is certainly a valid question...and a valid concern! Obviously the result of one would ruin the day of a lot of people.

Except for a few remote places, airliners always operate under IFR (Instrument Flight Rules) and are under the direct observation and control of ATC (Air Traffic Control). They have very, very strict separation criteria and there are stiff penalties to be had for the controller should he allow that separation to be lost. We also fly at altitudes appropriate for our direction of flight. Eastbound flights are at odd altitudes; Westbound flights at even altitudes.

And when all else fails, airliners are equipped with Traffic Collision Avoidance Systems (TCAS). TCAS puts a protective "bubble of time" around the plane and monitors all other nearby traffic, predicting whether or not they will enter that bubble. If it appears they will, it alerts us to the traffic. If it becomes more probable, it actually commands a climb or a descent in order to avoid a collision. But even cooler is that if the offending aircraft is also TCAS equipped, my TCAS will coordinate with the TCAS on the offending plane so that both aircraft maneuver away from each other. These maneuvers are not abrupt; TCAS has undoubtedly already saved countless lives...and the passengers never even knew it!

1 comment:

Joanna said...

Wow, that is REALLY fascinating.