Originally Posted by
HEATHROW DIRECTOR
Does the use of CPLDC involve the controller in extra work, e.g., typing on a keyboard when he would feel safer devoting his time to the real job?
CPDLC is faster than voice with regards to physically issuing the instruction (there's no typing involved). However, it is slower than voice with regards to the actual aircraft physically performing the instruction. This is due to the time lag in the instruction being sent and received by the aircraft, the pilot acknowledging the message, then the pilot initiating the clearance. Voice is more or less instant. There's also a massive variance in the amount of time it takes for a message to be acknowledged. Sometimes it can be more or less instant, other times several seconds and sometimes the message will time out and not reach the aircraft at all. Voice is always instant - assuming the pilot is paying attention of course! :o) - so most controllers (in the UK at least) just stick to that. Or only use CPDLC for non time critical instructions, e.g. frequency changes/asking for preferred cruising levels instead of headings or level changes.
In the UK there are also lots of restrictions for it's use plus the huge difference in reliability between ATN and FANS equipped aircraft. FANS is so unreliable that controllers will mostly only use ATN.
Also, if there are any pilots reading this, please stop announcing on the frequency when you call on that you're CPDLC equipped. It's a pointless waste of RT when it's busy. We can see when you're logged and will use it accordingly if need be. Thanking you in advance!