LNAV problem between right and left

[Claude Troncy 4]

Bonjour,

 

Approaching EHAM ILS27, I am fighting with LNAV which seems to mix up between left and right.

The lateral path is clearly on the left, but the plane wants to join the next waypoint by the right.

 

So I am certainly doing something wrong but I cannot see what.

Thanks

Cheers

Claude

 

 

[downscc 1,327]

Interesting but not enough to go on here... I see that next waypoint WPNB is bearing 280 per LEGS page and current TRK on ND is 186 so the turn the the right is not unreasonable. The missing information here is what came before... I am not familiar with EHAM and cannot assume how you got to the waypoint you just passed. Flight plan, arrival, approach transition... all these would help. Do you have current NAVDATA 1413 Rev 2?

[Claude Troncy 4]

Hi Dan,

Thank you for your answer.

Yes I have NAVDATA 1413.

Before the turn to the right everything was OK as far as WPNB-4 where NGX decide to take a shortcut on the left... And finally joined the next waypoint. The capture of the ILS was good but turbulent.... after arrival at the gate , cabin crew  told me that was too much turn ... :smile: 

I came from SUGOL.

Cheers.

Claude

 

[downscc 1,327]

APPROACH ILS27 FIX WPNB AT OR ABOVE 2000 FIX EH639 2000 RNW 27 TRK 267 UNTIL 3000

 TRANSITION SUGO1 FIX SUGOL AT OR BELOW 10000 AT OR ABOVE 7000 SPEED 250 FIX D292O
 SPEED 220 TRK 082 INTERCEPT RADIAL 112 TO FIX SPL FIX SPL AT OR ABOVE 7000
 TRK 062 INTERCEPT RADIAL 092 TO FIX WPNB FIX WPNB AT OR ABOVE 3000
 TRK 140 UNTIL 3.5 FROM FIX WPNB

Okay, problem is that the transition is not coded to include the procedural turn, note above that all it does is send you on a 140 track until 3.5 nm from the navaid then you are on your own until arriving back at the navaid WP.  Historically, Navigraph does not provide the pseudofixes necessary for procedure turns. They do build DME arcs for you and most RNP approaches are okay but it's very cumbersome to code the necessary pseudofixes to create an arc to a fix due to the limitations of the syntax in the sidstar files.

 

My recommendation is to be ready to intercede with MCP HDG to get the turn started in the correct direction just before WPNB-4, then while in the turn you set LOC mode to capture the localizer and your're home free after GS in APP mode.

[Claude Troncy 4]

 

 

My recommendation is to be ready to intercede with MCP HDG

Yes that's exactly what I did the others times.

I posted because as on the navigation display the turn is well displayed, I thought that the LNAV soft knew where to go.

Again thanks for the clarification.

Cheers

Claude