Transponder settings B747-400??

[Guest Nightflight744]

Hello guys,happy Easter!! Can anybody explain to me what these two switches at the Transponder/TCAS are for (B747-400)? Above and below if I read correctly and the other one Full/?? There is not much about it in the manual.I just flew my first flight on VATSIM and the Controller asked for Squawk Mode C. I thought it would already be on Mode C when I turn the knob to the right (TA). I then fiddled with these to other switches and then he got me on Radar. Next time I would like to set it up correctly from the beginnning.Thank you very much for your replies!!Fabian

[Guest nicam]

Above means when you are climbing the TCAS looks for planes above you,Below is the opposite of above, ie you switch to below when you are decending. Also while you are in FL you leave switch in middle position. you have to turn the knob to the right to get TCAS to work, then you press the traffic button in map mode. then you will see other plane in your ND. (you should see a tfc in you ND)Also to test TCAS switch knob to left and you should hear "TCAS systems OK"after tuning your squawk code you press the ident button.Michael

[Guest Nightflight744]

Hi Michael,thank you very much for your comprehensive explanation!! The TCAS system is working perfectly and now I also know what the ABOVE/BELOW switch does und the ABS/REL switch.To activate the Transponder you additionally have to press Ident. I did not know that. I thought turning the knob to any of the right positions would be enough.I will check it out on my next VATSIM flight.Regards,Fabian