Polar routes

[EHM-1001 Robert]

Hi mates,

I have seen a map of routes between Western Europe and Far East. Most of these routes go near the poles. I know we have many similar routes. Do you use to fly over the pole ? It is said that is a challenging task for a pilot.

[EHM-1242 Stef]

Hi Robert,

Made a couple of flights near/over the pole. It's nice when you see how much time one saves! Last one was from ESSA to PANC (EHM-C469), which came up to 87 degrees North (i believe). Flew it with the PMDG B744F, which displayed some unusual navigational behaviour though, which i dont know whether it is caused by FS9.1 or by the PMDG model.

Considering that on those latitudes the FS earth model has been stretched greatly longitudinally (in FS the world is flat. MS discovered first in 2007 that the earth is round... ) strange courselines were displayed in the navigation display, with all kinds of 'hooks' and curves in it:





Why should courseline 'drift of' (note that there is no waypoint!) north?? This happened in all sorts of varieties :[

Flying in VNAV was an absolute no-go and had to take her in HDG mode manually for some 3 hours to keep her on course. First when approaching the northern Alaska coastline i could slowly consider using VNAV again.

And, what you can also see in above (hopefully! First time posting embedded images...) is a phenomenon i am experiencing more often with the PMDG 744: that the aircraft just refuses to hold it's course. See how she is in a left bank where the path to follow is clearly 1,45 (XTC on FMC) miles to the right..? When it happens (does not happen always, say roughly every 2nd or 3rd flight) it normally is on East-West courses, and when about 3 to 4 hours into the flight (although have seen it also happen already after 1 hour into the flight)... Very frustrating and spoiling my fun in flying the PMDG 744 because one is always waiting for it to happen (and mostly it does somewhere)! :[

Am i the only one where the aircraft shows this kind of behaviour??? Checked the forums at PMDG but could not find anything in this respect there...

Na good, so much to flying the poles.

Oh, one more thing: in the MS world the global warming has already been thoroughly completed! Instead of ice and snow (which i wanted to see) there is just a giant expanse of OPEN OCEAN up there!

Aloha,
Stef
EHM-1242

[EHM-2155 Mariano]

Hum does that still happen with Direct - GPS routes in flight planner?

[EHM-1001 Robert]

Well,

it is strange a bit and in other hand "usual" !? I remember I have had some similar bugs with the PMDG. But in my case it was a bit more simple: it just turns in the wrong direction sometimes...and after 30-40 degrees of "mistake" it recognizes the trouble and turn back to the normal course. I remember it happened sometimes, but unfortunately I do not believe the FMC, and many cases fly it without LNAV mode. Also for SID and STAR I used to turn off FMC and fly her manually following the magenta line

Anyway, nice discovery about the poles. If I remember I have not flown a timetable flight yet there. I just made a testflight with the MD17...who knows why...but I saw ice ! A continous ice shelf was panning across a longitude. It was quite unreal but at least it was ice. More funny was the compass...I followed the route in FSNAV and the airplane icon was many times pointing 40 degrees off the course

Also I remember when I travelled from Paris to Seoul and back. Trajectory was shown on those small monitors onboard. The plane went high in a big curve from Korea to North-Europe, but the curve did not went higher than the coastline of Russia. That time I did not understood the curve...now I do not understand the curve being not so high

[EHM-1465 Dominic]

I can't say I've done much polar flying but I think these anomalies are realsitic ones, aren't they?

That's why the big jets have MAG / TRUE switches for the heading control since at polar latitudes the earth's magnetic fields interfere with accurate use of magnetic compasses causing track errors...

I don't know whether PMDG's rendition of this effect is accurate but seeing as their aircraft are generally very good I wouldn't be surprised if it was

[EHM-1242 Stef]

Hello gentlemen,

Normally am trying to do things by the book and as per checklist. Anyway, even though wanted to switch over from MAG to TRUE (if i am not mistaken in the Boeing manual at www.smartcockpit.com it is written at 78 degrees North it should be switched) this was not required as the PMDG 744 shortly before reaching this latitude makes the switch by itself when it deemes necessary.

I don't think these things are realistic. Am a nautical officer by trade and, although we do not go THAT far north, a courseline is always displayed as a straight line on such short distances (fly my ND normally set to 40 nm range). Note also that even if it would not be, the curve would have to point the other way, towards the south due to the nature of the greatcircle.

My best guess as to what one sees in the above is that MS FS is feeding wrong positional information to the 'aircraft', causing all these strange courselines (unfortunately have just one pic... :[ )

As to the PMDG phenomenon:
Robert, ofcours i meant i was flying LNAV. Sorry, my mistake. All these abbreviations sometimes gets mixed up... VNAV is ok and has never caused any problems. On my system it just happens slowly: she slowly starts wandering ofcours, coming back, staying there for a while, wandering of again - bit further this time, coming back etc. Until a certain stage where she just wanders some 3,5 miles ofcours and banks hard for a full circle in the wrong direction (i let her go once over Australia). After this then all goes wrong... Just like she does not know anymore what the hell :@ she was actually doing!

One day i'll find a cure... until then just hope for the best. I dont know where to look anymore or what to try.

As to the compass readings: yep, fully normal because near the magnetical pole the magnetic field does not have a directional component anymore, just the vertical component remains (which pointing straight down/up). Check the picture: HDG 219, magn compass indicating some 055!?

Cheers

Stef
EHM-1242

[EHM-1001 Robert]

Hi Stef,

it sounds for some reason the NAV hold mode gone crazy. Maybe your autopilot settings are not correct ? I tried to check autopilot settings but those are inside the AIR file coded for PMDG... did you use time compression maybe ? That have a bad effect on autopilot.

[EHM-1242 Stef]

Exactlt my thoughts when i am observing it happen: "has she gone totally lunatic, or what!?!?"

Have talked about this quite extensively with my brother (Niels) as well because on his system this behaviour can not be observed. Have compared a zillion settings already (including switching off/on gyro drift and the likes) but all to no avail.

Nope, don't do time-compression. When i fly, i fly real-time. Also on my long distance flights.

Who knows, perhaps it becomes better now that i have the FS9 update for the PMDG B744 installed that came with the FSX version they recently released (one thing i do not understand from PMDG though: when there is an update to the current FS9 version, why not make it available for public download for the users who do not own/want the FSX B744???) Haven't flown the FS9 B744 since installing the update. Perhaps it has improved now...

By the way, since we were actually talking polar flights here: slewed around a bit earlier this evening (installed FS Global 2008 and wanted to check what the world looked like after this. Really an amazing difference such mesh-software makes!! Can really recommend it! And: I now have a northpole! ) and the MS world ends at 89degr 30min North (guess same is South). You then run into a wall (literally!) and can go no further...

Thanks for trying to help out though. Much appreciated.

Aloha,

Stef
EHM-1242