Question About Arcs

I got a sort of niche question here. I’m flying into Paro using one of the charts they have posted on their AIP:

I can share this; it’s publicly available online from Bhutan’s Department of Air Transport:

You can see in between some of the waypoints there’s a number followed by the word “Arc,” take for example between PR744 and PR742. Usually when I see arcs their attached to some sort of VOR, but clearly in this situation the “7 Arc” isn’t attached to the only VOR on the chart, PRO.

Is there some special procedure I need to follow to fly these kinds of arcs where there’s no relevant VOR?


In IF we sadly only have direct lines, no curved ones and also no overflight waypoints which makes this somewhat hard to follow. The best option in my opinion would be to manually change the heading gradually to achieve a slightly curved turn in between the waypoints or to fly manually.

IRL you could enter the procedure into the FMC and the A/P would be able to fly accordingly :)


As Julian said we don’t have curves in the flight plan however Laura and some of the devs have expressed interest at having curves between waypoints.

In this case it’s an RNAV (RNP) chart. You won’t have many references to a VOR or a “traditional” NAVAID in these charts. They usually go off of GPS/NAV waypoints


I believe it depends on specialised performance criteria built into the specific aircraft FMC, a sort of high precision mode. So only certain aircraft types or even specific models in an airlines fleet will have the capability to fly these procedures on autopilot.

Ive thought about trying to manually fly them in IF, to recreate the arc track, but honestly these are usually pretty hairy approaches and there’s no room for errors, so it’s easier to let the AP fly direct tracks to each fix…

However that could quite easily put you in a mountain.

I have been working on a tool that allows you to recreate RF legs in IF, it’s not quite finished, but will probably be done within the week.

Here’s what it can do, this is the south RNP for 02 at MHTG.


wow very nice and impressive work there. Good job


Oh that’s so cool! Don’t forget to let us know when you’re done! I’ll be waiting patiently 😁


Will definitely be on the look out for that.

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