Wind / distance and flight time?

[FLY744F]

Hello guys

If I was flying 3210nm and and headwind of 44 mach 0.86 how would I calculate my distance and flight time?

Thanks
Fly744f

[John Golin]

Well distance would be 3210nm...

Time would depend on groundspeed - Mach / groundspeed relationship varies with Altitude.

[Jeroen Hoppenbrouwers]

Straight copy from
http://forums.vatsim.net/viewtopic.php?f=6&t=35425

1) Take the base distance of 1000nm.
2) Take your true air speed and determine how long it would have taken you to fly the 1000nm if there was no wind (for the example, let's take 500KTAS).
3) Multiply the number of hours needed to fly the original trip with the (average) headwind/tailwind component. (in this example 2h13m x 50nm/h head = 111nm)
4) Add the calculated miles to the base distance from 1) and you'll get what's called the "air miles".

So, we get 1111 air miles, with 500KTAS we get 2h 13m flight time. If we used ground miles (base distance) and ground speed, by dividing 1000nm with 450kts (effect of a 50kt headwind) we get 2h 13m flight. So what's the difference, then?

Well, if you consider that most performance tables (or charts) are based on a fixed TAS and variable distance, it's much easier (and less prone to errors) if you were to simply take out the fuel requirement value for 1100 miles, rather than taking the fuel requirement for 1000nm and then calculate the additional requirements with the fuel flow values.

[Hardy Heinlin]

In addition to what John said, the relationship to TAS or groundspeed also depends on the OAT which may change while maintining the same altitude. (When it gets warmer, the speed of sound rises.)

If you know your Mach and your headwind, it looks like your sitting in a well equipped flight deck :-) Why not read the groundspeed directly? And then ...

distance_nm / groundspeed_kt = hours_to_go

minutes_to_go = hours_to_go * 60


P.S.: To turn the hours_to_go value into a HH:MM display, e.g. hours_to_go = 6.9

Hours: 6
Minutes: 0.9 * 60 = 54

06:54