Ok well i only fly rc but have a sirous question. So jet plans have a system called tcas that avoinds to plans hitting each other. but the atc also does that so... if tcas tells you to climb and atc tells you to decend which order do you respect?

Here's a good primer on TCAS.

http://en.wikipedia.org/wiki/TCAS

At my airline we are authorized to deviate from an ATC clearance to comply with a TCAS instruction.

There was an accident a while ago (2002) involving a DHL 757 and a Tu-154. I won't go into too much detail here but basically ATC made an error handling these planes and they were brought to close together. They both had TCAS alerts. The 757 followed the TCAS instruction while the 154 followed the ATC intruction and ignored the TCAS which was the opposite instruction to ATC. Both planes collided and killed all board were killed. The ATC controller was later stabbed to death by a family member of one on the victims.

http://en.wikipedia.org/wiki/Bashkir...es_Flight_2937

See thats the thing i wa unsure about. if airline a says "Allways fallow TCAS" and ariline be says "Fallow ATC" you have the same poblem is there a hard an fast rule that is though in ground school.

I am not sure but I believe that in the US most airlines will follow the TCAS but I have never heard of a rule either way.

Flying Freak,
Your question was a little hard to follow with the typos, but I think I have it....

In the end, the PIC (Pilot in Command) always has the last say/final decision in what steps to take. He's in the best position to evaluate the situation.

Bob

SO if i understand everything corecctly there is NO rule of thumb tat piolots fallow. Does anyone other then me think this may be a problem?

You need to understand how TCAS works to get the whole picture. The TCAS units in the approaching aircraft "talk" to each other and determine who will climb and who will descend. Then they give the aural and visual commands in the planes. One will say climb and one descend and the event is over. All airline operator are trained to follow TCAS over ATC unless there is some extreme reason not to. ATC has no idea which plane is going to climb or descend since that issue was decided by the TCAS units in the planes. If TCAS says climb and ATC say descend, you climb - because the other plane is going to descend.