Hi all,
Yes, you are quite right, the output of the CADC feeds info to the altimeter without QNH correction, the pilot makes that adjustment.
So then, you ask, can the pilot change the altitude indicated on the radar screen of the ATC controller by simply changing his QNH setting, mode C?
The answer is a definite NO, as we have already mentioned, the mode C altitude info, fed from the CADC, is uncorrected for pressure variations prior to transmission, the radar controller makes these corrections.
Logical really!
The B747 Classic does what you want, when you want it!
Cheers