Hi,

 

Was doing the SID MEDAM4N from LSGG today and noticed after flying over the first waypoint (D8GVA) that the majenta line started acting weird and turned into an unflyable "rollercoaster" line that doesn't look very good (see 2 images here)... At that point the AP starting becoming crazy trying to chase the GC604 waypoint and I had to resolve making a direct to entry in the FMC to ESAPI to continue the flight.

 

Anyone else noticed some drawing problems on more complex SID and STARS?

Thanks

Anthony Brichart

 

http://fsfiles.org/flightsimshotsv2/images/2015/04/05/2a656d.jpg

 

http://fsfiles.org/flightsimshotsv2/images/2015/04/05/164631.jpg

 

 

 

 

 

 

This actually happens often for some departures.  The B777 is not a 'follow the magenta line' as much as the NGX is, the smart boxes are several decades old and now as new as the NGX,  Part of the problem is that the path prediction is guess work while you are sitting on the runway and not moving, and the curve may align itself correctly after the program has a speed to work with. Maybe.

 

As for the fix that has a wrong turn, that is usually a sidstar coding error that you should notify Navigraph of in their forum.  Sometimes a TURN RIGHT DIRECT or whatever would work better than the way their parser generates the procedures.

 

Final word, most problems occur with procedures that are non-RNAV.  I have LSGG but not this departure so I am guess this is a non-RNAV SID.

Just disregard the FD and turn towards the first waypoint.

(or better, hit HDG SEL and set a heading)

Then select the first waypoint and put it on top in the legs page - execute.

You should now have a proper magenta line.

 

I have seen similar things at other airports and they usually go away with the above method.

Looking at your two images, I suspect part of the problem is your speed.

 

I've not flown that particular departure, but looking at the map display and the chart itself, that initial turn is quite tight and probably not achievable at 250KIAS (even more so with a tailwind as you have in your picture: the turn radius at 300KTAS, plus the wind pushing you even wider, is going to be significant).

 

Whilst the procedure doesn't explicitly mention a speed restriction, I'd be considering 220kts maximum: possibly even 210kts until established on track to ESAPI.

 

As the FMC will be calculating the path based on the achievable turn radius, if you try and fly too fast you may confuse it and strange things may result, especially with conditional waypoints, VOR radials to intercept etc.