F214 Interpolation

[vegancruiser]

For the purposes of flight planning during PPL training (Qualifying cross country tomorrow, hopefully!) can someone please explain to me how to interpolate correctly for wind velocity at altitudes BETWEEN the levels given in the wind 'boxes' on the F214 (e.g. for 3000 ft), and then between adjacent boxes, should this be necessary. I've never fully understood the procedure involved and I'd be grateful for some guidance. Or, am I being too pedantic (bearing in mind again that I'm still a student)?

[Lone_Ranger]

Split the difference....they are'nt very accurate anyway

[SpannerInTheWerks]

Interpolate vertically within the relevant boxes and then horizontally between these adjacent boxes.

Same for temperature.

Just because you are a student on a qualifying cross-country doesn't absolve you from responsibility nor should you consider yourself any less affected by the weather!!!

Shame you haven't been taught this before today.

So, for example:

50N 05W

05 050 25 +07
02 040 15 +13

50N 0230W

05 040 25 +09
02 040 20 +13

For 3000ft (vertically) (say, in round figures):

50N 05W

03 043 18 +11

50N 0230W

03 040 22 +12

So if you're between the two points (horizontally):

03 040 20 +11

Nearest 5 degrees of wind direction is fine;
Nearest 5 knots of wind speed is fine;
temperature is above freezing (main point);

So, in this example: 03 040 20 and no known icing would be acceptable.

In more severe weather the gradients will be greater but the above will hold true in most cases.

[vegancruiser]

"Just because you are a student on a qualifying cross-country doesn't absolve you from responsibility nor should you consider yourself any less affected by the weather!!!"

SITW.. Of course I was in no way implying that I absolve myself of any responsibility - heaven forbid! I'm fully aware of my responsibilities with regard to flight planning and the supreme importance of the weather in this regard. I'm also aware that the information contained in F214, F215 etc. is inexact and that the actual conditions encountered in flight can vary greatly. However I do tend to favour exactness, even when the science itself is inexact and this is why I asked about the degree of accuracy advised when interpolating. You've answered my question comprehensively, for which I'm very grateful.

[SpannerInTheWerks]

It's a pleasure

All the best with your qualifier.

[Heston]

Oh c'mon guys, get real. Lets say you are looking at the forecast (forecast, note) for 1200z. What time are you flying? 1200z? No, thought not.


These things are to give you an idea of how the atmosphere is expected to behave in a general sense. Not to give you an accurate wind vector for flight navigation purposes.


For navigation you'd be better off looking at the ground wind at the start of your flight and making the speed and direction adjustment for winds aloft. Please, at least do this to check that what the F214 told you is still right.

[SpannerInTheWerks]

Oh c'mon guys, get real.

Hmmm...

For navigation you'd be better off looking at the ground wind at the start of your flight and making the speed and direction adjustment for winds aloft. Please, at least do this to check that what the F214 told you is still right.

T'other way round I should have thought (in any event, I find it difficult to imagine the winds aloft from a distance of 100 miles on a long cross-country!!!)?

These things are to give you an idea of how the atmosphere is expected to behave in a general sense. Not to give you an accurate wind vector for flight navigation purposes.

It's the best information available - and should be the basis of calculation for all flights, especially flight tests and 'qualifying' flights.

Apart from wind velocity, how would you know what the temperature will be at your planned level/altitude, unless you 'suck it and see' and depart regardless?

Maybe not too much of an issue if it's a summer's day and/or you can guarantee VMC and have the knowledge and experience never to be caught out - for the rest of us it would be preferable to know prior to departure what the freezing level is forecast to be.

[Crash one]

I'm a bit surprised at the QXC stage you haven't either been taught this interpolation or figured it out. How have you managed Navexes up till now?That said it's just a case of splitting the differences between speeds/temps given to them wot are missing, shimples, innit?

[Gertrude the Wombat]

I'm a bit surprised at the QXC stage you haven't either been taught this interpolation or figured it out. How have you managed Navexes up till now?

Most people just fly around at 2,000' all the time, so no interpolation needed.

[Crash one]

I'm at 56N about 3West which isn't on the spot wind chart, So no wind, no weather, no temp. No interpolation required. Brilliant.