fart
First thing to note is that a Flyby waypoint has to be coded into the aircraft FMC as part of a procedure. The waypoint can still exist in the FMC database for use by the pilot at any time but (at least to my knowledge) if he inserts it as a waypoint himself then he has no way of making it anything other than Flyover waypoint. All to do with the ARINC 424 coding protocols, which gets very heavy
If you are clearing a pilot to an intermediate waypoint on a coded route and it is a Flyby waypoint, then it makes no difference, the FMC will continue to treat it as such.
In terms of what you can expect the aircraft to do at a Flyby, it will probably commence the turn a couple of miles before the waypoint, passing maybe a mile or so abeam it in the turn.
At the moment there is no clear guidance on the separation (spacing) to be applied between SID/STAR routes, however PANS-OPS does provide containment formulae albeit primarily to do with obstacle clearance calculation. These calculations can be made for Flyby waypoints to show the likely swathe where aircraft following the procedure can be found, or in other words how far they are likely to deviate from the nominal track. At the moment route spacing 'rules' only exist for airspace outside TMAs although it is now recognised that similar guidance needs to be supplied for routes such as those you are asking about.
If you're into maths, geometry, and trig, then procedure design is for you !! ICAO DOC 8168 has all the gory details.
------------------
PPRuNe Radar
ATC Forum Moderator
[email protected]