Hi guys,

 

I have a problem with the direct to function on the 737 NGX.

 

When I proceed a "direct to", we can see on the PFD et ND that I'm 0.4 NM Right of my route and this offtrack is still increasing. When I was reaching the waypoint the plane was 1.0 NM offtrack!! I've inserted the correct wind in the FMC.

 

Sometimes around 0.4 – 0.5 NM the plane tries to go back on its route but it's still flying on a parallel track and it's still continue to deviate.

 

Does someone else noticed that problem when you proceed to a direct route?

 

Regards,

 

Vincent.

 

Probably related to weather/turbluence - what happens when you do it with all weather disabled?

It's the same story with no wind/turbulence. I also have deactivated the thermic effect in FSX.

I don't think it's coming from the wind/weather:

 

In this case the wind is 267/25 TAS = 453 kt and the track is 176°. So we have X =3.3° . Heading 179 is correct to compensate the wind component.

And as I said, I have the same problem with no wind. Furthermore the plane is deviated to the right, which would mean that it's over-compensating the drift. This is not the case as we can with the calculation.

 

Vincent

It could be a magnetic variation thing maybe - what route is this exactly? I'll try it.

HI Tabs,

 

It was an european flight from LOWW to LGKF.

 

Flight plan : LOWW SID SASAL UZ21 BABIT UT23 TADAM UM127 VAL UN732 KRK UH51 KESAL STAR LGKF

 

FL390 cost index: 40

 

If I remember, the first direct to was from TADAM to MOJ (freq 308).

 

Regards,

 

Vincent

When you do a Direct To, the route is from PPOS to the next waypoint. Not sure if that's significant on the NG FMC, on one real world FMC I've seen this led to lateral drift as there was no From Waypoint as such.

RW, the plane will start the turn when you execute, but it won't roll out being direct, it'll head back to a line from where you executed the DIR to the DIR waypoint. If there was a bug with that, it would seem to have a decreasing error, not an increasing on.

Yes that's it. As I know from a friend who is F/O on 777 the FMC draws a new magenta line from your present position to the next waypoint and the plane will follow it. But in this case it deviated all along this new route and when it reached the waypoint the plane was 1.1 NM right to the waypoint.

 

Edit: Oups, Spin737 answered the first ;-)

I made the flight again and this time with no weather. After a direct to, the plane deviated again from its route. I tried to reintercept the route with heading select and then reengage Lnav but it didn't work either.

 

Vincent.