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There are plenty of approaches with fly-over waypoints. The first to come to mind is Colmar, where the IAF HO is fly-over, for obvious reasons.

EGKB Biggin Hill

I have noticed that fixes which form a holding fix are fly-through. It seems to be a convention, regardless of terrain

That Colmar hold is a huge distance from any terrain, in terms of even the crudest accuracy of flying a hold using GPS. Also if HO is used as an IAF, one is at 3000ft+.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

I have noticed that fixes which form a holding fix are fly-through. It seems to be a convention, regardless of terrain

Yep. This obviously is needed as the point is to fly over it.

But then not here at Dusseldorf but the MA turning point is fly over.

Last Edited by JasonC at 25 Mar 18:45
EGTK Oxford

A fly-over waypoint is coded differently to a fly-by waypoint…. your approach approved GPS will not anticipate the turn for a fly-over waypoint.

YPJT, United Arab Emirates

Maybe this discussion shows that there is more to PBN ops than just knowing what buttons to push on the GPS box…

ESKC (Uppsala/Sundbro), Sweden

In terms of theory, sure, but not in terms of flying any of these tracks with a GPS.

Taking my example in post #28, the GPS switches to 1nm FS (full scale) 30nm away from the airport, and when it reaches KA20F it starts to wind this down to 0.3nm FS, reaching 0.3nm FS sometime before RW20, so even the prehistoric KLN94 will fly you right down the centreline of the runway.

Looking at holding patterns, say post #30, the fly-through nature of the holding fix is equally taken care of by simply flying at 1nm FS the whole time, and any intercept of the inbound track (towards the holding fix) will take you over the fix to a very high degree of accuracy; way way within the tolerances of the holding pattern whose protected area is after all is probably designed to be flown by a 747 doing Rate 1 turns… This is an old fallacy in IR training, where the holding pattern is taught to be flown to a high accuracy, using various weird devices like gates, while the protected area is actually huge.

Administrator
Shoreham EGKA, United Kingdom

AnthonyQ wrote:

A fly-over waypoint is coded differently to a fly-by waypoint…. your approach approved GPS will not anticipate the turn for a fly-over waypoint.

And there can be a good reason for that. In the example above of DL007 in post #31, the fly-over ensures that a turn isn’t made until after the wp. Not in this case, but there could have been an obstacle (mountain) to hit if the turn were anticipated as for a fly-by wp.

LSZK, Switzerland

I think the reason DL007 is a fly-through wp is because they want you to fly the missed approach from the runway (obviously) to that point and not to somewhere else. Missed approaches are normally flown on the runway heading (or track – another debate – but on autopilot flying a GPS track on the way in, it will be the track) and a fly-through wp there is the only way to code that requirement. There is no way to code a “fly Track X”.

IMHO the reason is just that, not what happens after DL007. I also say that because turn performance after DL007 will depend hugely on the aircraft type and the avionics. So the protected area there must be big enough, not just for GA but for somebody doing this at 200kt+ (and possibly +5000fpm).

Administrator
Shoreham EGKA, United Kingdom

Why are we even discussing this?

EGKB Biggin Hill

Peter wrote:

There is no way to code a “fly Track X”.

Yes there is. All the Fx leg types. Lots of departures are coded with tracks to altitude or distance legs. They obviously could have done so here but chose one other method which is a fly over waypoint.

EGTK Oxford
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