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Guest Blue Ridge Dx

A question about flight plans?

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Why are there waypoints every 25 miles or so on a 500 mile flight plan? Why not go from one VOR to another that are spaced 100 miles apart. You could have the one behind you on nav2 and the one in front on nav 1. Noobie question but thought I'd ask...rgds,billg

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Hey Bill,In the real world, its rare to see the enroute portion of a flight plan filled with intersections or FMS waypoints. However, when a flight is planned to follow a DP or STAR, it is fairly common to see many 'waypoints' in close succession.For example...and do forgive me if I'm a little off, as I'm doing this from memory... The VXV.MACEY2 arrival (MACEY TWO arrival, Volunteer Transition) into Atlanta Hartsfield is VXV..SABIN..MACEY..WOMAC..LOGEN/vectors to final.There's just about 100 miles between VXV and SABIN intersection, while the MACEY, WOMAC, and LOGEN intersections are all very closely spaced. While I'm sure there are other reasons, a major one is for Vertical Navigation. That is, there are multiple crossing restrictions at these intersections. Depending on which runways are in use, you must cross LOGEN at 13,000 and 250kt, or WOMAC at 14,000 and 250kt. The point behind it all is to properly sequence a large amount of arriving traffic.For the enroute portion, real world flight plans use a combination of Direct routing, and flying along Jet Routes. When flying Direct between VOR's, the distance between those VOR's cannot exceed 140nm. This is called CLASS I navigation, and is meant to keep the aircraft within the 'service volume' of at least one VOR. Jet Routes use a combination of VOR's, Intersections, and FMS Waypoints. I'm fairly certain that flying on a Jet Route will keep you in the service volume of at least one VOR, thus fulfilling the CLASS I navigation requirement. I'd have to check to be sure, though.So for realism's sake, I usually plan my flights using J-Routes, or for flights below FL180 I file V-Airways. And when flying direct between VOR's I limit leg distance to less than 140nm...Hope that helps you.Best Regards,Nick

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