Any way to calculate Required Time of Arrival/RTA manually when flying oceanic?

[Reece Arcinas]

Is there any way to calculate the RTA or Required Time of Arrival when flying oceanic. Normally, our FMC does this for us, but if you are in a plane that uses the default fsx gps for example, then they do not calculate RTA which means you probably have to do it manually when using fsx gps aircraft. Can you tell me how to do those calculations in an easy way? Thanks VATSIM Community!

[Andre Almeida]

1 knot is equivalent to 1 nautical mile per hour.

Meaning, if you're flying at 500 knots (groundspeed) you will be travelling 500 nautical miles in an hour. 

Knowing this the calculation becomes fairly straightforward. Let's say you are 300 miles away from your next waypoint, flying at 460 knots groundspeed.

300/460~=0,65 hours. Multiply it by 60 minutes in an hour, and you get 39 minutes. This means you'll arrive at the waypoint in 39 minutes.

Add 39 to current time, and you get your ETA.

[Andreas Fuchs]

You could also run and connect LittleNavMap to your FlightSim, load the route in there as well and thus get the times, too.

[Torben Andersen]

If you fly with Mach number, you'll need to convert TAS to Mach (or vice versa), which is temperature dependent.

Either using a formula (google is your friend) or a table like the attached.

RAM AIR - OUTSIDE AIR TEMPERATURE CONVERSION CHART.pdf

Edited April 17, 2021 at 11:12 AM by Torben Andersen

[Robert Shearman Jr]

11 hours ago, Torben Andersen said:

If you fly with Mach number, you'll need to convert TAS to Mach (or vice versa), which is temperature dependent.

Either using a formula (google is your friend) or a table like the attached.

RAM AIR - OUTSIDE AIR TEMPERATURE CONVERSION CHART.pdf 597.89 kB · 4 downloads

... unless you use your groundspeed, in which case you can just use what's showing on your GPS.  Since that also accounts for wind, it's probably the more accurate calculation.