The Gol Crash and TCAS

I’m sitting here at the Eye for Travel conference in Chicago listening to a session talking about blogging, so I thought it would be a great time to use the wi-fi in this frozen room and do a little writing.

The most interesting news today involves the unearthing of details of the crash of the Gol 737-800 with 155 people onboard. It seemed very strange when it happened because all newer aircraft of this type should be equipped with Traffic Collision Avoidance Systems (TCAS) that would have encouraged at least an attempt to avoid a collision.

These TCAS systems give an audible warning in the cockpit of each plane when two of them approach each other giving specific directions on how to avoid the accident. When a pilot hears TCAS alerts, he/she is supposed to follow instructions immediately and ignore any other directions that may come from air traffic control or instinct. As an example, this should have prevented an accident in Europe in 2002, but while one plane followed instructions, the other listened to air traffic control (which gave opposite instructions) and the planes collided.

Back to Brazil, what seems strange is that neither aircraft seem to have attempted evasive action. In the end, they were both cruising at 37,000 ft and the Gol flight crashed while the private jet landed with this damage:

Yeah, that’s a missing winglet, and they’re lucky to be alive. Interestingly, New York Times columnist Joe Sharkey was onboard the private jet and addressed the accident in this week’s column. He noted that the flight was at 37,000 ft, but now it sounds like they should have been 1,000 feet lower.

CNN reports today a couple of very interesting things. They cite another report that the private jet missed or ignored an instruction to descend to 36,000 ft and that the transponder may have been turned off. The problem with the former is obvious – if the flight descends, the accident doesn’t happen. The latter, however, is a little more complicated.

Let’s go back to TCAS. The only way TCAS systems can detect other airplanes around them is through transponders. Each aircraft turns on a transponder for identification purposes during the flight. If the transponder was turned off, the Gol plane never would have seen the private jet coming.

We don’t know what happened for sure yet, but these initial accusations have been enough for Brazil to refuse to allow the American pilots of the private jet to leave the country during the investigation.