747 Waypoint Problem

[Contactdepture 3]

p3Dv4:  On approach, the flight line (purple) turns several miles before the next active waypoint. Even though the waypoint is in the FMC and says it is next, the plane will show that it will turn before it making landing a little difficult.  I usually compensate by using heading select to the waypoint and then turning manually. Clearly, this should not happen. Anyone know what I am doing wrong??

Thank so much!

[downscc 1,327]

Welcome to the PMDG forums, please note their rules ask us to sign all posts with our full name.

I cannot visualize the approach you are describing.  What kind of approach?  Is the "next active waypoint" the FAF  and how far from the runway is it?

There are two basic types of waypoints or fixes: Fly By and Fly Over.  All fixes are Fly By unless specified as Fly Over by the published terminal procedures.  This means you will not normally fly directly over a fix but fly by it if there is a change in course.

[pracines 823]

24 minutes ago, Contactdepture said:

the flight line (purple) turns several miles before the next active waypoint.

You may be flying too fast - we don't know, because we don't even know what airport you're talking about. For all we know you are trying to fly an approach that a 747 cannot (is not authorized to) fly. 

Tell us more details, several miles can mean 10 or 4 for all we know. 

44 minutes ago, Contactdepture said:

the plane will show that it will turn before it making landing a little difficult

The FMS/AP will never make landing difficult if programmed/used correctly; if its turning "too soon", its trying to help.

I think (it sounds like) speed is the issue here. FLAPS 10 +5 speed is usually the max speed by the time you are turning final.

Some have had issues with arming the Autoland too soon.

Dan's advice and points could very well apply as well.

More information is needed.

[Contactdepture 3]

Ok, sorry for all of the ambiguity.  

I program PFPX and import the flight plan.  When I check it before take off (not even in the air yet), you can see that there will be a premature turn even though the way point is displayed and loaded correctly in the FMC and I am still on the ground. So speed has nothing to do with this. Changing the SID, makes no difference. So for example, I was flying into JFK on a 13L approach from the north. AROKE was the next active waypoint, but the flight line would turn a few miles early. Then, after the turn, TELEX was next and then CAXON before 13L. The flight line predicted a turn that would actually bypass these two waypoints (even though they were in the FMC and lit purple showing active in the cockpit) and turn just ahead of CAXON. 

 

I must be doing something wrong. It happens at all different airports, no particular to JFK. 

 

Not sure how to post media, but I would like to show you a screen shot..

 

Any thoughts?  Thanks so much.

Ken Rose

[thibodba57 462]

6 minutes ago, Contactdepture said:

Ok, sorry for all of the ambiguity.  

I program PFPX and import the flight plan.  When I check it before take off (not even in the air yet), you can see that there will be a premature turn even though the way point is displayed and loaded correctly in the FMC and I am still on the ground. So speed has nothing to do with this. Changing the SID, makes no difference. So for example, I was flying into JFK on a 13L approach from the north. AROKE was the next active waypoint, but the flight line would turn a few miles early. Then, after the turn, TELEX was next and then CAXON before 13L. The flight line predicted a turn that would actually bypass these two waypoints (even though they were in the FMC and lit purple showing active in the cockpit) and turn just ahead of CAXON. 

 

I must be doing something wrong. It happens at all different airports, no particular to JFK. 

 

Not sure how to post media, but I would like to show you a screen shot..

 

Any thoughts?  Thanks so much.

Ken Rose

Speed still has everything todo with this.  Just because you aren't in the air doesn't mean the aircraft isn't planning ahead.  I'll refer you to downscc's post above.  Unless a point is designated as a flyover it will be considered a flyby which means that the aircraft will lead a turn at a pre-planned point to ensure the aircraft remains inside it's corridor.  Do not use HDG SEL, trust the automation to do it's thing and verify thru-out the turn.  Also flying an RNAV Departure you should always remain in LNAV for lateral guidance, but that's a side note.

[Contactdepture 3]

 will look into the flyby etc. I appreciate the advice

Edited October 6, 2018 by Contactdepture

[downscc 1,327]

32 minutes ago, Contactdepture said:

So for example, I was flying into JFK on a 13L approach from the north. AROKE was the next active waypoint, but the flight line would turn a few miles early. Then, after the turn, TELEX was next and then CAXON before 13L.  The IAF

Still vague.  Are you flying the ILS 13L?  The IAFs are either COVIR, KMCHI or BUZON... you should be entering the approach from one of those and by the time you are at TELEX you should have captured the localizer.  None of the 13L approaches have an AROKE, or any of the arrivals so I still cannot picture what the problem is.

[Contactdepture 3]

I this particular flight, I was just taking what PFPX  gave me in terms of flight plan altered it because it didn't make sense, but I see your point.

[pracines 823]

With this new info this has nothing to do with flyby.

This is the predicted FMS speed that you will eventually reduce like all 747 pilots do during approach.

If you want to see better alignment of the course line all you have to do is reduce the predicted (small font) FMS speed and make it more like 150 instead of 240  or 210 or whatever the FMS is predicting.

 

[ph-cxz 28]

What is your navdata revision because aroke doesn’t exist as a waypoint.

[JRBarrett 3,034]

Waypoints AROKE, followed by TELEX (in that order) might make sense to set you up for an runway 13L approach at JFK, but ONLY if you were approaching the airport from the south, because AROKE is south of TELEX. 

AROKE is over the Atlantic, south of Breezy Point, and TELEX is over the borough of Queens, but is pretty much on the extended centerline of runway 31R/13L

CAXON, makes no sense at all. That waypoint is over the eastern end of Lake Ontario 359 miles northwest of JFK!  If it appeared on your legs page after TELEX, it would probably result in a very strange routing on your Nav display indeed.

Not sure what AIRAC you are using for the aircraft and PFPX. CAXON may have been located somewhere else previously, but in the current cycle it is over Lake Ontario.

[ph-cxz 28]

The ils approach into kjfk for runway 13L has TELEX and CAXUN as points. I would assume that CAXON is CAXUN. And Aroke doesn’t exist in version 1810 when searching for it on the charts app.

[JRBarrett 3,034]

10 minutes ago, ph-cxz said:

The ils approach into kjfk for runway 13L has TELEX and CAXUN as points. I would assume that CAXON is CAXUN. And Aroke doesn’t exist in version 1810 when searching for it on the charts app.

The OP may have misspelled CAXUN in his post. If, however, it was entered in the FMS as CAXON, it would certainly have produced a corrupted Nav display. 

AROKE is definitely a current navigational waypoint. It is present in the Jeppesen Nav data in my ForeFlight app, (which is intended for r/w navigation) It is located on the 224 degree radial of JFK at 12 nm.

It is also present in the 18-10 PMDG Navigraph wpNavFIX.txt file with the same lat/lon is shown in ForeFlight.

[ph-cxz 28]

33 minutes ago, JRBarrett said:

The OP may have misspelled CAXUN in his post. If, however, it was entered in the FMS as CAXON, it would certainly have produced a corrupted Nav display. 

AROKE is definitely a current navigational waypoint. It is present in the Jeppesen Nav data in my ForeFlight app, (which is intended for r/w navigation) It is located on the 224 degree radial of JFK at 12 nm.

It is also present in the 18-10 PMDG Navigraph wpNavFIX.txt file with the same lat/lon is shown in ForeFlight.

Your right but I was looking at the navigraph charts which apparently don’t include that waypoint. Which means it should be in the next chart update I suppose.

[JRBarrett 3,034]

23 minutes ago, ph-cxz said:

Your right but I was looking at the navigraph charts which apparently don’t include that waypoint. Which means it should be in the next chart update I suppose.

If it’s an enroute RNAV waypoint it may not appear on any standard charts. 

Edit: AROKE is the initial fix of the ILS 04L approach at KJFK.

Edited October 6, 2018 by JRBarrett
additional info