FS2002 FLIGHT PLANNER?

[Guest]

Hi i was putting in one of my flights and i see that it is incorrect.The flight path is going off course is there a patch or update for this? please help....

[wsieffert 0]

A little more detail may help. When you selected the takeoff airport and the destination airport, what did you use for the type flight, Direct GPS, High Level Airways, Low Level Airways, VOR to Vor? Did you select "Find Route"?If you did all the above, did you go to the edit tab page and view the route? Did the route get you to the destination airport? If so, did you select any of the different way-points and delete the ones you didn't want? Did you grab the red line and place it over a replacement way-point.If not, try those procedures. The planner sometimes wants to make you go in the wrong direction. The only way is to manually edit.

[Guest]

I too have wondered about Flight Planner routes. They seem to be "great circle" routes which is not a problem on short flights. On long flights however (several thousand miles) the direction your aircraft must follow seems to constantly change, i.e., if you fly from Chicago to London you may start off steering 45 degrees to stay on the indicated route but if you stay on that route you'll end up "veering" severely off the flight track indicated by the green line. What I don't understand is why one has to frequently change the flight direction to "hit the target" airport. Why doesn't one simply set the direction of flight that takes you to your target? I assume it has something to do with spherical trigonometry which is far over my head. Thanks for any thoughts you have to share.Chuck

[Guest GalacticCowboy]

>I assume it has something to do with >spherical trigonometry...Yup. :) Gosh, you're taking me back to my college days...There are a couple different things coming into play here. First, a "projection" is how we describe a spherical object (the Earth) as a flat object (a map). Every projection system has built-in error because of the problem of mapping a sphere onto a flat surface. Deciding which to use is a tradeoff because in order to gain additional accuracy in one regard means that it is less accurate in others.The various types of projections can be broken down into several categories: "equi-distant" - the distance between any two points is accurate (conic and asimuthal projections, often centered on one of the poles); "equi-area" - one square inch anywhere on the map represents the same area (there are quite a few of these, but one downside is that they are generally only accurate for smaller maps representing defined areas - a state or country, for example.); "conformal" - the angle or direction between any two points is accurate, but scale is not (Mercator, etc.)The most widely used, and the one you're probably most familiar with, is called the Mercator Projection, which is a conformal projection. On a Mercator map, a line drawn between two points represents the "heading" between those points. However, the exaggeration of the upper latitudes means that, when mapped back onto a sphere, the lines curve.How does this apply to flight planning? The map in FS (and in any flight sim or utility that shows the entire Earth) is a Mercator projection or some variant. Therefore, you might draw a line from New York to Paris that says you could fly a heading of 080 (I have no idea if that's right, I just picked a number. :) ) but when mapped back onto the sphere it actually is a much longer path because it takes you far to the south of the actual straightest line. If you were to draw a line on a distance-accurate projection, the shortest line would appear to curve when drawn on the Mercator map.Here's another way to look at it. Unless you are flying east-west directly over the equator or DIRECTLY north-south, in order to fly a "straight line" heading, you (or your autopilot) are constantly, imperceptibly, actually flying a curved route. Sure, you might fly straight for a while, but eventually your compass gets far enough out of kilter that you correct your path. If you were able to actually force the airplane to always fly straight ahead regardless of the compass heading, you'd discover that your compass heading would change over time and, unless you'd planned for this, you'd end up somewhere besides where you intended. That's what a great-circle route is. Your plane flies straight ahead the entire time, even though the compass heading changes.If you want a little extra brain pain, go to your favorite search engine and search on "map projection". :)

[Guest]

Kurtis,Thanks for the great reply. I kinda get it. You apparently stayed awake in math classes.Chuck

[Guest RonB49]

Hey Chuck,Here's something to try and it's less complicated than projections, trig, etc. Get a piece of string and a globe (I had to go to the attic and find mine) and lay out a great circle route on the face of the globe.I was prompted to do this when I used the FS Flight Planner to chart a route from Orlando to Frankfurt. My route took me right up the East coast of the US and when I was about even with Boston (still on a heading of about 45 degrees), I couldn't stand it any longer and went to the attic. My route brought me into Frankfurt on a Southeasterly heading. The string and globe proved to me that the curved route was the shortest distance between two points on the globe.R-