OnCourse Software

Good morning,

Recently made a simple flight FNLU to FNHU in Angola. The route was direct from a VOR at FNLU to a VOR at FNHU, both of which required removal from the plan for PFE purposes - fair enough. I put an extra waypoint in at about 25 miles for FNHU which I expected to be the point to contact Approach.

When I compiled the plan in PFE it whacked an extra XXX waypoint in after that extra waypoint. That in itself isn't totally unexpected, I have seen it happen before. There is no way to tell exactly where it is, and you can't do anything about it anyway.

What actually happened on the flight was that I was kept on heading 120 all the way to about three miles from the airport before contacting Approach, who promptly turned me almost round on myself onto course 025 for several miles to get me back to a respectable point to be vectored to the appropriate runway. This is time-consuming (especially in a DC-3!) and completely unrealistic.

I don't think I am doing anything wrong, but please tell me if I am.

Any XXX waypoint popped in to your plan after your Top of Descent point is a pain anyway, because it invariably prevents your being instructed to descend at the right time - although that wasn't an issue on this occasion. One solution would be to make XXX points editable. Another (not quite as effective) solution would be to prevent the system putting XXX WPs in withing 25 miles of the destination airport.

Best regards,

John

Hi John

Bad flight plan I'm afraid!

Look at the co-ordinates for your last waypoint (VHU) and your destination. The last waypoint was actually on the airport. You would have received a warning about this when loading the flight plan, but you chose to ignore it.

Quote:

waypoint.0=FNLU, A, S8* 51.19',E13* 13.33',+000230.00,Tramp:,-998,-998,-998,0,0,RWY~07,:Tramp
waypoint.1=VNA, V, S8* 50.43',E13* 14.51',+000000.00,Tramp:,-998,-998,-998,0,0,,:Tramp
waypoint.2=WP1, I, S9* 27.08',E13* 37.38',+000000.00,Tramp:,-998,-998,-998,0,0,,:Tramp
waypoint.3=WP2, I, S12* 23.45',E15* 29.29',+000000.00,Tramp:,-998,-998,-998,0,0,,:Tramp
waypoint.4=VHU, V, S12* 48.27',E15* 45.08',+000000.00,Tramp:,-998,-998,-998,0,0,,:Tramp

2021-03-19_111210.jpg (377.6 KiB) Viewed 1232 times

waypoint.5=FNHU, A, S12* 48.17',E15* 45.04',+005587.00,Tramp:,-998,-998,-998,0,0,RWY~11,:Tramp

dmarch wrote: *

Fri Mar 19, 2021 11:20 am

Look at the co-ordinates for your last waypoint (VHU) and your destination. The last waypoint was actually on the airport. You would have received a warning about this when loading the flight plan, but you chose to ignore it. :o

Ouch! That hurts!

Nothing could be farther from the truth actually. I certainly did not choose to ignore any warnings!

This is the flight plan as originally created and loaded into PFE:
It includes VORs VNA and VHU which are critical to my navigation. But I do understand that PFE needs them removed (and warns me so), so that is exactly what I do:
But it is Waypoint 6 that I am pretty certain is the cause of the problem. Waypoint 5 (WP2) is approximately 25 miles out and is where I would expect to be contacting Approach.
Waypoint 6 seems to be fixed in place and unremovable. If I were able to remove it I feel sure all would have worked as expected.

John

Oops, sorry about that, I didn't notice you'd removed WP6. However, checking again I don't really see what the problem is because you were vectored for a reciprocal approach and to me it looks very good. Yes you were handed off to Approach at the XXX waypoint, which incidentally would not normally happen as XXX waypoints are not included after the last waypoint. When you delete the last waypoint though the flight plan is not re-processed. To achieve what you're after... being handed off to Approach at WP 5... you would need to remove WP 6 at source so there would then not be an XXX waypoint between WP 5 and your destination. Having said all that the resulting approach vectoring would be the same or near abouts.

Thanks,

Yes, it worked OK but my problem was a "please explain" from my employer as to why I used so much fuel (joke) and a heckling from my passengers who disembarked 15 minutes after arrival time.

Your suggestion is what I already planned to try when that occurs again, and it must be said usually it doesn't. Much of achieving what you want as an end-user with PF3 is understanding how the software thinks! Thanks for confirming that.

Best regards,

John

Quote:

Much of achieving what you want as an end-user with PF3 is understanding how the software thinks!

Are, well now, that's another common misconception... PF3 doesn't 'think', it's entirely event driven

dmarch wrote: *

Sat Mar 20, 2021 2:47 pm

Are, well now, that's another common misconception... PF3 doesn't 'think', it's entirely event driven ;)

I know that and you know that, but replace the word "thinks" with "works" if you prefer.

John

Hi Dave,

Just a follow-up note to say all is working well now, as proved by several subsequent flights under different conditions. Despite what you said, I am now finding I get a much more direct approach path, more like this: And there is another bonus, my aircraft profiles now cause me to be instructed to descend at more-or-less the right time - something I was previously finding unreliable.

So the motto definitely is to not depend on PFE removing unwanted waypoints but to remove them yourself beforehand. I had not realised there would be such a significant difference.

I expect this does not arise for most users but as one that never uses things like FMCs and GPSs, I am almost always flying towards a VOR on the last part of a flight, and that VOR is usually at the destination airport itself. Changing the way of creating the flight plan for PFE is the solution!

Best regards,

John

For best results the last active waypoint in your PF3 flight plan should be no closer than about 20 miles out. As you say, waypoints that are too close interfere not only with vectoring but also the descent profile. PF3 does not automatically remove waypoints that are too close but does display a warning, I think if any waypoints are less than 15 miles from the destination (unless the warnings have been turned off). Waypoints that are too close can be deactivated on the waypoint screen. You can include the terminal airport VOR in your flight planner output but it should be deactivated in your PF3 flight plan because you are not actually going to cross it in most cases, you will be vectored well before you reach it.

Hi John,

Thanks for the feedback and I'm delighted you now have things working as planned.

Just one point re your sentence (as Dan mentioned)

Quote:

So the motto definitely is to not depend on PFE removing unwanted waypoints but to remove them yourself beforehand.

PF3 doesn't actually remove ANY waypoints... we used to do so in PFE but that was dropped for PF3 and more recently providing a means by which you can do so yourself.

Anyway, glad all is well for now