Originally Posted by ATC Watcher
one has to remember the definition of RNP 0.3. . the GPS is not designed to align you with centre line and to maintain you there , but just to align you with the runway with a precision of 0.3 of a NM orv 500 meters.
In theory... but do you really think a system would be approved for RNP 0.3 (eg RNP Approach LNAV) if
all it could do was put you within 0.3nm of the Centreline? That is "miles" off and you'd never get in on any min-vis approach. What about RNP-AR at RNP 0.1? "What are you complaining about? You're only 200m off the centreline!".