Thales FMGC Arrow after waypt

[CaptainMongo]

What is the purpose of the arrow after SLM waypoint? (Thales manual says, "Horizontal arrows with WPT beside a fixed waypoint on the flight plan page indicates that the A/C must turn at fixed waypoint in the indicated direction.") but that doesn't make sense to me. TIA.

[RUMBEAR]

Waypoints can be flyover or flyby (i.e with turn anticipation). Flyover waypoints commonly have a triangle symbol beside them to identify as flyover, however commonly on SID's / STAR'S where the flyover waypoint involves a turn, the arrow replaces the triangle symbol to indicate the waypoint as "flyover" plus the turn direction.

[CaptainMongo]

Is there a minimum turn requirement before the arrow will display? It will only display an arrow on a SID/STAR? Also for my own edification, where is that written? thanks.

[underfire]

Typically, waypoints are flyby. Flyover have a /0 next to them if I remember correctly. Very, very, very seldom is a waypoint coded at flyover, did I mention very seldom? With flyover, you have to 'fix' a bunch of things you dont want to have to fix...

The turn anticipation is a very unusual beast, and in reality, a bit unpredictable depending on the ac/fms combo. (which is why the obstacle areas are so huge)
I cannot see any waypoint with a turn being flyover, in a real world, that just does not make sense.
http://i68.tinypic.com/fjfe34.jpg
Looking at the latest 'T' shaped RNAV, one can see over time the leg angles have changed for the 90 to 45..

This was a study, testing the variations in the tracks with different angles, with different combinations of ac/fms...these are all flyby, testing to see how the ac handle different angles of legs with turn anticipation...(mostly to show how RNAV was crap vs RNP)
Notice how the 90 degree turn performance vs the 45 degree turn performance being close to track relate. (the hold pattern test was a bit amusing)

http://i65.tinypic.com/1zqvllu.jpg

[Capn Bloggs]

Underfire, nonsense. Have a look at YBBN CORAL 4 SID. You will note that it doesn't appear turn back on itself to intercept the waypoint-to-waypoint leg that you have shown in that diagram...

Besides...relevance?

the arrow replaces the triangle symbol to indicate the waypoint as "flyover" plus the turn direction.
I learn something every day! :ok:

[underfire]

stalker..Where does it state that this is YBBN? I see that you are grounded once again Bloggs!

the arrow does not replace the triangle, the arrow shows turn direction. So you learned nothing, a shock for you I suppose.

In case you need to comprehend relevance, refer to posts above that reference flyover/flyby and turn anticipation...do I need to provide a reference for that for you?

[RUMBEAR]

Hey Guys,

I can't back my claims by an FCOM reference. However from observation when a JEPPESEN chart shows a waypoint as overfly then a triangle appears next to that waypoint. When the overfly waypoint also includes a significant turn then the arrow appears indicating turn direction ( instead of triangle ).

Some examples of this include Osaka ( Kansai ) Rwy 24L Helen one departure ( initial waypoint ) and also the initial waypoint for Taipei Rwy 23L and R Octan departure.

So the Arrow might not Replace the Triangle but certainly appears instead of!

Purely an observation of the Thales FMS fitted to the AIRBUS I fly.

Have only observed this on SID's. I must agree with under fire about STAR's and Instrument approaches using overfly waypoints and turns together. Probably pointless for terrain clearance considerations. However SID's in the part of the world I fly, Noise Abatement or traffic separation is commonly the reason behind the design of the lateral path.

[Capn Bloggs]

stalker..Where does it state that this is YBBN? I see that you are grounded once again Bloggs!
I'd didn't say it did, UF. I was merely responding to your sweeping statement "Very, very, very seldom is a waypoint coded at flyover, did I mention very seldom? With flyover, you have to 'fix' a bunch of things you don't want to have to fix..." showing you a flyover waypoint. Given that I operate in a backwater, I am sure there are many others around the place.

the arrow does not replace the triangle, the arrow shows turn direction.
So you're calling out Rumbear?

In case you need to comprehend relevance, refer to posts above that reference flyover/flyby and turn anticipation...
Yep, ONE, in a bracket...

[underfire]

From the FMS Operators Manual.
"Overfly Waypoints - An asterisk (*) after the waypoint identifier indicates that it has been designated as an overfly waypoint. "

Originally Posted by Underfire
the arrow does not replace the triangle, the arrow shows turn direction.
So you're calling out Rumbear?

"Thales manual says, "Horizontal arrows with WPT beside a fixed waypoint on the flight plan page indicates that the A/C must turn at fixed waypoint in the indicated direction."

In regards to flyover, while they may be used, again, it is very, very seldom. There are some waypoints that are flyover without being designated as flyover, or will act as a flyover. If you fly an offset, it will automatically remove the offset at the FAF, you cannot offset the FAF.

[Lantirn]

The arrow can be displayed also after an altitude.