Any benefits to planning northern Latitude flights vs straight line?

[JSMR]

Since FS2004 world is a cylinder rather than a sphere, is there actually any benefit to planning Great Circle tracks vs a more direct line? I'd be interested to see if there is any difference in time, fuel etc.

 

In the real world of course there is a benefit to this type of planning. But I'm wondering if its a pointless exercise other than to make it 'as real as possible'?

 

Only one way to find out I guess. :p

[JSMR]

Interesting to note is that the route i flew today - LHR-LAX was a ground distance of 4826nm according to simbrief. I only went as high as 58N. I think some plans on FLightaware were around 62N.

 

Not planning any waypoints, same route, and Simbrief draws a Great Circle track. Distance 4730nm.

 

I did a basically straight line track in Simbrief. Distance 5317nm.

 

In the real world, both the first two would most likely be the most beneficial, shorter and more fuel efficient. In FS2004, as I said earlier, I'm wondering if its a pointless exercise and the straight line/longer track is actually...shorter?

 

Found this tidbit online :

 

In reality of course, aircraft travel on great circle routes. If I'm not mistaken, FSP computes the point-to-point distance from departure to destination using a SPHERICAL earth (since spherical trig calculations of distance on the earth's surface are rather simple, just using longitude and latitude).

 

In FS2004 however, the flights are actually simulated on a series or mercator projection cylinders, each of which covers a sector of longitude. This makes long range flights artificially much longer than they would be in the real world (great circle navigation doesn't actually occur in FS2004) and also much longer than the spherical earth calculation used to compute the point-to-point distance.

 

This effect is not much of a problem on short distance flights, but is much more pronounced on long-range flights like from England to Malaysia. The aircraft model likely has an artificially long range to compensate, and make it still capable of reaching that distance, but the simulated distance in FS2004 you have to fly is much longer than you would fly in reality.

[defaid]

A great circle route is the most direct on a sphere. On a panelled, truncated ovoid as in FS9, I'm not so sure. The maths is a long way beyond me...

 

If FS9's Earth was a cylinder the answer would be obvious -- unroll the cylinder and fly the same heading along the entire route. I guess that's what you mean by a straight line track. FS9's Earth is actually ovoid and is cut off above a certain latitude, something that's clear from the fact that you do need to follow an approximately GC route to reach your destination directly.

 

If it were a cylinder then a direct route planned in FS9 from LHR-LAX would have a departure heading 180° away from the opposite route LAX-LHR.

 

In FS9, I think the "Direct" function on a GPS gives the shortest route. I always assumed that it was giving FS9's closest approximation to a great circle route.

 

If someone can do the maths, I'd be very interested but I think it would depend on the specific shape of the ovoid. I use Super Flight Planner for my planning and find that it gives different leg lengths from a spherical distance calculator; it's made me curious about what geometrical model SFP is using. It seems to match FS9's GPS, which is half an answer.

 

Do you know what projection Simbrief uses? How either Earth appears on a flat map projection depends on the4 projection and a straight line drawn on the map is not a good indication of distance.

 

In the real world, planned deviations from GC routes are usually for land (rescue) and prevailing wind rather than for geographical efficiency.

 

D

Edited December 19, 2022 by defaid

[g5flyer]

Well, at the end of the day, you are simulating real world procedures I would guess. It all comes down to how realistic you want to be.

 

Rick

[JSMR]

My head hurts, D.

I have no idea what simbrief uses. I was using different options, from a true GC track vs the direct line (basically a straight line on paper between the two ports.)

I should have downloaded them into FS9 and loaded them into the GPS and see if the distances are actually the same.

And that’s a good point using the direct to function as I’ve never done that using a long flight. I always go through simbrief.

Might be one to experiment with.

 

 

And yes very true, Rick.

I wonder though if the actual distance is longer with a Great Circle track then reality? I guess that’s my point. At what point in FS9 does it become shorter/longer?

 

 

Interesting on the flight yesterday. I used FSGRW for my winds, and based my departure of the real time in the early 70’s as far as the hour of the day. The simbrief winds were 3-4 hours ahead as it doesn’t do historical winds. The winds though were pretty much the same.

 

So everything matched up pretty well. I even stepped climbed before simbrief told me too. The time of the flight was slightly longer then planned and the fuel burn, which initially was slightly ahead, ended up being more by the end by nearly 10,000lbs.

So maybe that’s the answer? The routing north was TOO far north to be worthwhile in FS9.

 

At the end of the day, of course it doesn’t matter. But it’s one if you like to plan it well. Especially when fuel is tight on 10+ hour flights on something like a 747-100.

 

Maybe I’ll just add 10-15,000 lbs extra to counter the ‘longer’ distance.

[JSMR]

Slight update, FS9 planner direct to show a GC line identical to Simbrief. Maybe that is after all the shortest way?

[ViperPilot2]

I fly the Magenta line. Now that I figured out how to work Nine's infernal GPS instrument, it's easier??!?

 

A long time ado I bought Eric Marciano's EasyFMC, that ties in to the GPS (I guess)... time to read the Manual again!

 

:p

[JSMR]

I fly the Magenta line. Now that I figured out how to work Nine's infernal GPS instrument, it's easier??!?

 

A long time ado I bought Eric Marciano's EasyFMC, that ties in to the GPS (I guess)... time to read the Manual again!

 

:p

 

 

 

Don’t worry, it’s 2022. We’re tolerant of all people! :D

[defaid]

My head hurts, D.

 

:D :D

 

Mine too now. I had a play last night with a GPS direct route between MM0Y and SBCO. Conveniently they are at pretty well the equal latitudes but in opposite hemispheres.

 

It's convenient because the track is symmetrical about the equator, which means, following the magenta line, I could leave MM0Y on 118°, cross the equator on 136° and fly over SBCO on... 118°

 

5025 nm

 

So, thinking about paper, projections, cigars, eggs and rubber sheets, I reasoned that I ought to be able to fly a fixed heading of 127° and arrive at my destination. Seems logical, right?

 

 

But I couldn't measure the track distance because the flight analysis Alt+O, A craps out every now and again. The data recorder AFSD only gives distance from a fixed point which I think is not the same thing.

 

So on to Plan B. Fly a fixed ground speed and note the time. That would have worked.

 

But... MS did something very odd with their 3d geometry. On FS9's map, that fixed 127° left me pointing almost directly east and with SBCO abeam with a track error of about 450 nm. Everything else still showed 127°.

 

I had a similar result when flying 130°.

 

I wasn't flying a gyro-precession spiral as all the realism sliders were down at the don't-mess-this-up-for-me end. So I'm thinking that the FS9 mathematical model for the surface of the Earth is probably some nasty lash-up that can't be recreated either in 2d or 3d.

 

In any case, a "Direct To" on the GPS should give the shortest distance between 2 points. Whether MS made it so is questionnable.

 

***

 

Incidentally, if you have a globe and a length of cotton thread, you can find the shortest route very easily by pulling the thread tight over the surface between PoD and PoA.

 

D

Edited December 20, 2022 by defaid