Question for the pilots

[MaggieL]

More on the crash...
http://story.news.yahoo.com/news?tmp...iner_crash_152

Apparently the russian pilot has a TCAS alert that told him to climb. TCAS (Transponder Collision Alert System) is a simple-minded cousin to ADS-B; it's a simple reciever that listens to transponder replies in the neighborhood and compares the reported altitude to the current altitude. If it hears a reply that reports something too close to the current altitude, it assumes that the other airplane is a threat; if it was at a very different altitude it's not a factor, and if it's too far away to hear it's not at factor (yet) either.

So...the TCAS aboard the airliner was apparently telling the pilot to climb to avoid the cargo jet, and seconds later the ground controller called on the radio and instructed the same pilot to *descend*. According to the article, the TCAS information is deemed more accurate, and policy is that it to be immediately followed, even in the event of a conflict with ground instructions (while informing the ground controller as soon as possible).

In another touch of irony, German ATC as trying to reach the Swiss controler to tell him *their* conflict alert was flagging the two planes as converging, but the only telephone line to the Swiss controler was apparently busy.

The accident investigation reports on this one will be interesting.