GBAS is already available on most commercial aircraft, in fact, for most, it is free, one just has to ask for it to be installed.
GBAS systems are installed at virtually NO airports.
The FAA is reluctant to consider GBAS at the airports becuase they consider GBAS as a single point failure system. (and they spent a bazillion dollars on things like MLS and WAAS)
GBAS is NOT RNP. There are RNP transitions to a GBAS final procedures, but RNP and GBAS are independant.
RNP procedures use non-comp baro-vnav for vertical guidance. GBAS provides vertical guidance with an ILS look alike, but unlike ILS as a beam, GBAS is a signal which isnt interrupted like a beam, and contains all of the approach guidance.
Yes, the GBAS signal can even include turns.
Getting past all of these issues with the regulators has taken many, many years. The aircraft that are already equipped to use GBAS will be recycled into beer cans before the onboard system is ever used.
Last edited by underfire; 26th October 2013 at 22:24.