Hi,In the 2nd (advanced) tutorial on page 15 I'm told to rotate the TCAS mode selector switch to RA/TA when still standing at the gate which puzzles me a bit since I always learned you should only do that after you are cleared to enter the runway at the same time you turn on your landing lights and the strobe lights after beeing cleared for take off. Is this a mistake in the tutorial or did I miss something or maybe the TCAS and the RA/TA mode works differently in such a highly automated a/c as the MD-11 is?

Hi Richard, A post a few months ago actually set me straight for the 1st time. I too thought of it exactly like that. That's what I learned in a couple tutorials as well as AOA's dvd's on the 747. The tcas is actually used for ground control it appears so most companies (or at least those whose posted their comments about it) SOP's were to turn it on prior to taxi, and if I remember correctly is a rule at some airports that have the available systems that use the tcas for such a thing.I have no idea the name of the post I'm referring to, but think it was titled something like, "real world questions"...

Richard, Dan,the reason to do this is not TCAS, but the transponder. And since those two systems are turned on together you just select whatever you need for the flight later on, in this case RA/TA.These days a lot of airports use a sophisticated ground movement radar for their ATC. Those radars use the mode C and S functions of the transponder, hence at some airports it is a MUST to turn on the transponder at the gate already.To see what marvels that mode S can transmit to ATC, have a look at this document:http://www.eurocontrol.int/msa/public/stan...l_overview.htmlSo no this is not an error in the tutorial document, just state-of-the art technology. I do nit know however how things look right now regarding mode S and the US airspace. Very often the US is way behind regarding its state of the ATC equipment, compared to Europe.But at least there's some area in the US where ADS-B is already operational. And ADS-B is even better, it is the future. TCAS can not be used on ground, but ADS-B can, and is much more precise... What to do to get an aircraft sending an ADS-B signal? Well a BASIC description is simple: Plug your GPS or IRS data into the mode S transponder and send that away. Of course to take full advantage of ADS-B the avionics need to be built around this as well. However none of this highly advanced future ADS-B stuff is operational yet on the airliners, not even on the B787 or A380. But it will be coming soon...Regards,Markus

Wow! Thanks for your thorough answers guys, this is what makes these forums so great...you never stop learning new stuff!

Yes indeed, thanks Markus for the much more detailed explanation of it. Much more thorough than the post I was trying to remember even though I probably hacked up the little I did remember, hehe. I'll still look for the other post just since it became a great one for reference for other Q&A's also, and post the link if I get lucky.

AOPA has been advocating ADS-B for years, and it's been in an operational test for almost a decade in Alaska. Gee, for the FAA to do something in less than 10 years is remarkable.