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I was researching worldwide airway designations when I stumbled upon this airway in Brazil: G678 with an MEA of 15,000 feet and a distance of 594 NM (nautical miles) between navaids.

It's drawn between the BSI and ATF VOR's. Mid-airway around S12°50.12' W52°4.38'.

Flying at 15,000' with BSI at elev ~3500', the line-of-sight is 166 NM. And as far as I know a high altitude VOR reaches out to 130 NM, maybe more, but certainly not 300 NM, right?

The "G" designation is for a non-area navigation route per ICAO annex 11. So it's a non-RNAV route. It's even colored black (vs. blue) on skyvector.

A, B, G, R for routes which form part of the regional networks of ATS routes and are not area navigation routes.

So, how can it be flown?

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    $\begingroup$ When doing line-of-sight calculations, did you factor in that SBBR is at an elevation of almost 3500'? I'm sure part of the route can be flown "from" the SBBR VOR and part can be flown "to" the SBAT VOR. $\endgroup$ – Ron Beyer Sep 27 '16 at 18:51
  • $\begingroup$ @RonBeyer done, thanks. $\endgroup$ – ymb1 Sep 27 '16 at 19:21
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    $\begingroup$ By 594 nm, do you mean nanometers? $\endgroup$ – John Dvorak Sep 27 '16 at 19:50
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    $\begingroup$ @JanDvorak I was wondering exactly that coming from the network feed. :-p $\endgroup$ – Constantino Tsarouhas Sep 27 '16 at 19:53
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You are correct that VOR's rarely have a range of more than 200 NM. However, Alta Floresta VOR (ATF) is colocated with an NDB (and DME). In spite of less accuracy, NDB's have a much greater range (partly because their signals can travel as ground waves). This makes it possible to have a very long segment on the G678 airway without other navigation aids. When leaving the coverage of Brasília VOR/DME (BSI), you should be able to pick up ATF NDB.

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Several options:

1) Fly the route using GNSS navigation, as the VOR stations do not offer full coverage along that route.

2) Fly the route using INS, if the aircraft is so equipped, in the segments of the airway where VOR service is spotty.

3) Select a different route between these two points which has additional terrestrial navaids along it that all offer good signal coverage along the route.

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    $\begingroup$ True, but the airway is non-RNAV, i.e. non-RNAV equipped planes should be able to fly it. $\endgroup$ – ymb1 Sep 27 '16 at 19:35

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