Radio navigation near north pole

[cjp]

I'm asking this question here, because I expect to find a lot of people here with similar interests and maybe even some real pilots:

Some time ago I was flying in Flight Simulator. I remembered my own flights between Amsterdam and Tokyo, which went over northern Siberia. I also remembered old pictures showing the Amsterdam-Tokyo route going over the north pole. I thought a bit about this difference, and I concluded that going over Siberia is the shortest, but wasn't possible in the old days when the Soviet Union was there.

So I wanted to try the old route. I also figured the old planes probably didn't have a very long range, so I planned a stop at Anchorage in Alaska. Also GPS didn't exist yet, so I only used VOR and other radio navigation aids.

I have some experience in Flight Simulator with flying on VOR beacons, but this route got me into trouble. The problem is that is comes very close to the magnetic north pole. Also, there weren't any beacons around there, so the only thing I could do was to fly on my compass. Which isn't a good idea close to the magnetic north pole of course.

I could of course ignore everything, and just try to fly in a straight line as good as possible, but I was afraid that even a little bit of wind could blow be so far off-course that I couldn't detect the first beacon when arriving at Alaska.

How do real airline pilots handle this situation? How did they do this before the GPS era?

 

[Redburne]

As far as I know, the navigators had to rely on inertial navigation systems for flights with no possibility of radio navigation. A well known IN system (according to Wikipedia) was the Delco Carousel, which is even available for FS.

And don't forget that the old practice of shooting the sun or stars also works from planes. According to the article, it was used until the 60s when it was replaced by inertial navigation.

When KLM opened its polar route to Japan in 1958, both options may have been available.

 

[blane]

Oh I tried to go to the south pole in FSX once. It's very freaky. The problem is that the simulator's inherent navigation does not work properly ot the poles. It cannot even display the graphics correctly at there are only vectors going straight to the "pole singularity". I think this is a problem with all MSFS versions.

Apart from that, if you're just close of the poles, the flight planner does work. I made a flight with a Mooney Bravo from London to Boston, fueling up at the Thule Airbase:

http://gc.kls2.com/cgi-bin/gc?PATH=LBC-LHR-IOM-RKV-THU-YFB-YWK-FSP-BOS

I used the flight planner to do direct Airport-Airport flight as there are no actual VOR roads up there.

 

[Hielor]

http://en.wikipedia.org/wiki/Korean_Air_Flight_902

 

[David]

NDB's should still work, also, although I don't know to what extent they actually are used.

 

[Urwumpe]

NDB's should still work, also, although I don't know to what extent they actually are used.

Too short range, AFAIR. You can hardly place a NDB on floating ice.

 

[cjp]

http://en.wikipedia.org/wiki/Korean_Air_Flight_902

Yes, that is very much like what I did. Except I noticed a bit sooner that something was wrong, and I checked the map of Flight Simulator. When navigating, I consider looking at the map as cheating, so I only do that when I'm lost and want to find out what I did wrong.

When you pass over the magnetic pole (or come close to it), the compass direction you should follow changes very rapidly. I had a flight plan that anticipated for this, with time, ground speed and compass direction. The problem was I didn't know my ground speed, only IAS. So, after a long cross-Atlantic flight, I didn't know exactly when to expect to arrive at the magnetic pole. And compensating too soon or too late will give a very similar route as flight 902.

 

[Urwumpe]

It cannot even display the graphics correctly at there are only vectors going straight to the "pole singularity". I think this is a problem with all MSFS versions.

Yes, the problem is that MSFS uses cylindrical coordinates internally (Orbiter uses Cartesian internally). At high latitudes, the numerical errors will be higher this way, but cylindrical coordinates allow simpler math for simple low flying airplanes than Cartesian coordinates.

 

[blane]

http://en.wikipedia.org/wiki/Marambio_Base

That's the southernmost I flew in my campaign, That's also where VOR/NDB coverage ends.

 

[Urwumpe]

http://en.wikipedia.org/wiki/Marambio_Base

That's the southernmost I flew in my campaign, That's also where VOR/NDB coverage ends.

Hmm, looks like a cool location. Anybody planning to make a add-on of the base with the cool signal orange buildings?:speakcool:

 

[golden_eye]

I actually took a class on international navigation a couple semesters ago. I was flipping through my book but can't find anything, though I do remember planning a polar route. I'll look some more and see what I can dig up.

 

[Moonwalker]

I could of course ignore everything, and just try to fly in a straight line as good as possible, but I was afraid that even a little bit of wind could blow be so far off-course that I couldn't detect the first beacon when arriving at Alaska.

Be aware that flying a straight line by holding a certain magnetic heading, but also true heading, only is a straight line as long as you fly along the equator or any meridian. Otherwise you'll fly a "rhumb line" which results in a deviation from your planned arrival when flying long distances. Keep in mind that meridians converge to the poles. Your aircraft follows that convergence in case you always fly the same heading, or in other words: you'll fly spiral instead a straight line.

A straight line, which means flying orthodromic, is a GC ("great circle") which is a continuous change of aircraft heading (as long as you don't follow any meridian or the equator). For example: a straight flight or great circle from Frankfurt to San Francisco would begin with a heading of 323° and end with a heading of 209°.

Great circle navigation is done by modern flight management computers these days.

But even for a Boeing 747-400 for example, navigating north of 73° northern latitude and/or south of 60° southern latitude still is critical. The innertial reference systems and nav computers are based on magnetic headings. Crews have to be aware that the IRS and the radio nav aids can't be used reliable beyond that latitudes. But navigating beyond that latitudes is unsual anyway.

If you don't have a GPS available, you can only navigate visually or by dead reckoning navigation which is not very reliable (at least not on very long routes) in case you use a magnetic compass, which you have to. You can also calculate and fly orthodromic routes manually which requires some exercises and knowledge.

 

[Andy44]

Flying a rhumb line would be acceptable for many flights, say NY to London. As long as you don't fly too close to the pole a rhumb line shouldn't waste too much fuel. Wasn't rhumb line navigation popular back in the old days when a compass and an astrolab were all you had?

Would be handy if the Earth had a second set of poles, we could call them the East Pole and the West Pole. Then when you approach the singularity at any pole system you just switch to the other. But launching GPS satellites is probably less expensive than building giant electromagnets...

 

[Moonwalker]

Flying a rhumb line would be acceptable for many flights, say NY to London.

For small aircraft, basically performing VFR flights, flying rhumb lines is rather usual and negligible. But for flights from Europe to the US east coast, great cirlce navigation has an economic impact already. Flight planning and navigation for jet aircraft flights across oceans and continents is based on great cirlce navigation today. Even if an aircraft is going to intercept a preprogrammed route during flight, the flight managagement computer calculates a great circle track to intercept the desired route. But also if you enter very long intersections, for example for crossing the atlantic ocean, great cirlce navigation takes place automatically.

As long as you don't fly too close to the pole a rhumb line shouldn't waste too much fuel.

Well, flying from Frankfurt to San Francisco on a rhumb line, which wouldn't even exceed 50° northern latitude (because it would require a heading of 262°), would increase the trip distance from 4.937 NM up to 5.685 NM.

Crossing north pole regions during long range flights is not a problem for modern jet aircraft by the way, as long as you don't have to land somewhere beyond 73° northern latitude, using radio nav aids and/or an innertial reference system while in darkness or IFR conditions.

 

[pattersoncr]

...Would be handy if the Earth had a second set of poles, we could call them the East Pole and the West Pole. Then when you approach the singularity at any pole system you just switch to the other. But launching GPS satellites is probably less expensive than building giant electromagnets...

When I was on the boat, our Fire Control System (used for tracking contacts) had a function that would do exactly that for operating at high latitudes. It placed an imaginary set of poles on the Equator to make the internal math less wacky. Never saw it in operation though.

 

[Bill LeClere]

celestial navigation

there's a simulated sextant you can use in fs. I haven't tried to tuse it near the poles, but did a big flight around Hudson Bay with it and it worked fine. Takes a bit of work, though.

Bill