Great Circle Route Surprises?

Graueradler

Graueradler

Pattern Altitude
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Apr 11, 2005
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Russellville, AR
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Graueradler
I was just looking at flightaware and noticed a flight tracking from WNW to ESE over northern Arkansas was a Honolulu to Atlanta flight . I'm sure that it'll make sense when I stretch a string between those points over the globe surface but it was unexpected. The plane ahead of it was an LAX to ATL flight.
 
Here is an online Great Circle Mapper:

http://gc.kls2.com/

...and the result. Doesn't look like it is fine enough scale/detail to help you much.

-Skip
 

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Everskyward said:
I was pretty surprised a while back when I plugged in Denver to London...
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When I lived in England we used get flight that diverted to us instead of going home to Anchorage as it was closer to land in the London area form where they were flying. Blew my mind away that it was a short flight to Alaska while a longer flight to Ohama, NE.
 
The strangest part is, if your great-circle routing takes you through Chicago App's airspace, it magically gets a bubble and moves...
 
SCCutler said:
The strangest part is, if your great-circle routing takes you through Chicago App's airspace, it magically gets a bubble and moves...
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Chicago's new airspace design to keep GA out.
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Greg that is amazing. One question I know compasses go all goofy over the pole. Do you rely on GPS in that area? and What did pilots do over the pole before GPS?
 
Graueradler said:
I was just looking at flightaware and noticed a flight tracking from WNW to ESE over northern Arkansas was a Honolulu to Atlanta flight . I'm sure that it'll make sense when I stretch a string between those points over the globe surface but it was unexpected. The plane ahead of it was an LAX to ATL flight.
Click to expand...

It's amazing how much misdirection has been programmed into one's brain over the years by looking at all those generic flat graduated mileage scale maps in school isn't it? A polar region map changes everything.
 
AdamZ said:
Greg that is amazing. One question I know compasses go all goofy over the pole. Do you rely on GPS in that area? and What did pilots do over the pole before GPS?
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Well, we use a flight management system that takes the best navigation source available. That is nearly always the GPS system. Above about 70 degrees north latitude, we also use true headings rather than magnetic.

Previously, they used a system called grid navigation. To be honest, I have no idea how that works.
 
I found the first flight ever over the pole was by Robert Byrd in 1926. Ya know he did it by nothing more than good old dead reckoning and probably very primitive pilotage since there was dang lilttle to recognize and the ice masses were difficult to map at the time. The little, if any, would have been done by ships.

These are a set of YouTube videos about the first commercial flight over the pole using INS. It was a Pan Am 707. Pretty interesting!

Part 1

Part 2

Part 3

Part 4
 
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AdamZ said:
Greg that is amazing. One question I know compasses go all goofy over the pole. Do you rely on GPS in that area? and What did pilots do over the pole before GPS?
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I did quite a bit of that in the AF. We used inertial guidance systems. That was long before GPS, and the inertial nav systems were actually very accurate. Depending on the plane, we kept the system updated with all the normal inputs of heading, airspeed, etc. On a/c a little larger, doppler was incorporated, as well as astro trackers. It was kind of neat to watch the tracker search for a star when you engaged the thing.
 
2256Q said:
I did quite a bit of that in the AF. We used inertial guidance systems. That was long before GPS, and the inertial nav systems were actually very accurate. Depending on the plane, we kept the system updated with all the normal inputs of heading, airspeed, etc. On a/c a little larger, doppler was incorporated, as well as astro trackers. It was kind of neat to watch the tracker search for a star when you engaged the thing.
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Never saw an astro tracker. How did it work?

On our plane we had inertial nav and a celestial port that the nav guys would use to with the installed sextant.
 
smigaldi said:
Never saw an astro tracker. How did it work?

On our plane we had inertial nav and a celestial port that the nav guys would use to with the installed sextant.
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The astro tracker was/is an extremely sensitive light sensor. It is housed in a small glass dome that protrudes from the a/c skin. On the 111 it was mounted forward of the windshield on the nose, on the B-58 it was at the top of the spine about a third of the way back along the fuselage. There's a computer on the panel where you input the location of the star you want to lock onto in terms of sidereal hour angle, star declination and star lat-long. When engaged, the tracker head begins an outward spiral search for the star's light until it finds it and locks on. The data is transfered to the nav computers and updates position. On the ground you can watch the little tracker head spiral around inside its dome. The dome itself is perhaps 2" in diameter and protrudes 2 or 3" above the skin.
 
I would be surprised if Greg even looks at a compass once each flight in that airplane.
 
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