Oceanic "Position" wind reporting

[blue up]

I've asked this on a few websites, emailed our management and training department and e-mailed NATS but haven't yet had a reply, so.....I'll ask the experts!

When reporting a position on the oceanic routes, do you require a wind report in TRUE or MAG? Our FMCs give the wind in mag but that is not so useful for plotting when you get near Canada where the magnetic variation is high. Have we been giving duff information for years? Our manuals 'suggest' reading straight off the FMC but I cannot find anyone who can give a specific answer and a reference to prove it.

Can anyone help?

Thanks

[fisbangwollop]

This from an enroute doc but if you read the end note re data link I guess whatever format the data link would pass it in is good enough.....:cool:

5.4 Meteorological reports
5.4.1 When voice communications are used, oceanic area control centres shall designate, from among the aircraft intending to
operate on the organized tracks, those which shall be required to report routine meteorological observations at each prescribed
reporting point. This designation shall be made by the oceanic area control centre delivering the oceanic clearance, using the phrase
“SEND MET REPORTS”, and should normally be made so as to designate one aircraft per track at approximately hourly intervals.
Note.— When air-ground data link is being used for meteorological reporting during flight, no aircraft observations by voice
communications are required, in accordance with Annex 3, 5.3.1.

[Spitoon]

It should be deg TRUE

The reference is ICAO Annex 3 Appendix 4, and in particular, Table A4-4.

[DFC]

In general -

Wind directions other than for a landing and take-off shall be expressed in degrees true.

Refernce is ICAO Annex 5 (Units of Measurament to be Used in Air and Ground Operations) Table 3-4 (Standard Application of specific units of measurament).

The only time wind direction is expressed in magnetic is when ATC tell you the wind for take-off or landing. Every other sourse gives the info in true.

To be specific -

ICAO Annex 3 (Meteorology) Appendix 4 Gives the requirements for Air Reports;

2.2 Wind Direction

Wind direction shall be reported in terms of degree true, rounded to the nearest whole degree.

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Now a question for you - do you upload winds to your FMS? If so do you correct every wind at every point for variation? :)

[HHI OPS]

Is the document available in the net? I am not at work for the next days.

[blue up]

Thanks, Spitoon. Looks like we've been doing it wrong for years!

DFC. Generally I enter winds only for the actual, +1000 and -1000 levels but our flightplans give us magnetic winds, so it is all fine from our point of view.

If anything gets fired back from our management dept, I'll post it here for further discussion.

Cheers:ok:

[blue up]

Wifey reports a phonecall from "NUTS" (a soft-porn mag in the UK) asking her to tell me they want a report in TRUE WIND. I'm assuming it was NATS, not NUTS.

Mind you, it might have been NUTS.:O

Problem solved, then. Report Oceanic winds in degrees TRUE.

[BOAC]

Thanks blue up - good link - you can see the effect of a warm front there:ok:

[WetFeet]

A lot of Oceanic position reports are made automatically nowadays, no voice reports required. These reports include wx. Maybe someone can tell us what wind those pos reports give.

[DFC]

True wind.

FMS always works in true and then at the last minute converts the bits you need to be told into magnetic using local variation before displaying the heading / track to you.

In a very simplistic way - A to B, great circle track - convert to average track, apply wind and hey presto, you have average wind component etc etc.

Try doing the same with magnetic figures when the variation goes from 20E to 20W in random uneven stages along the track.

If you fly EFIS, have a look at the wind readout in numbers in the FMS (true) and then look at the wind arrow on the screen (magnetic). The difference should be the variation. Switch your reference to True and see what happens.

These days aircraft will happily fly all day and night referenced to true north. It is only to please the pilot / atc / current chart publications that magnetic is used.

Even if your company provides you with a PLOG showing only magnetic track, magnetic winds etc etc, the computer will have done the calculation using true. Anything else would be overly complicated.

I think that I made the point earlier - if you upload winds through ACARS / AFIS etc then they will be true winds and your FMS will be happy. You would have to be really bored / have too much pre-flight time to look up the local variation at every winf point and adjust the figure. :}