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Wind limits and JAR-OPS Planning Minima

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Wind limits and JAR-OPS Planning Minima

Old 6th Apr 2008, 11:09
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Wind limits and JAR-OPS Planning Minima

JAR-OPS 1.297 lists planning minima criteria as

(i) RVR/visibility specified in accordance with JAR-OPS 1.225; and
(ii) For a non-precision approach or a circling approach, the ceiling [...];


No mention of wind.

However, JAR-OPS AMC OPS 1.297 Application of aerodrome forecasts, which gives more detail, says in its table:

Mean wind: Should be within required limits;

What policies do others use for wind limits for flight planning purposes please? Do you have wind speed limits, crosswind limits? Are these based on an interpretation of JAR-OPS or a company policy?

(Please note I'm not asking about the captain's criteria for making an approach based on reported wind, nor the landing itself, just the planning minima.)
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Old 6th Apr 2008, 21:23
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I have worked as a dispatcher. Sorry for being too lazy to cross check JAR-OPS and the OM-B, but thatīs the way I handled it:
Some airplanes have a maximum allowed XWC, whereas others have a "demonstrated" XWC, you find this usually in the OM-B or the AFM.
If you have a "demonstrated" XWC, you can exceed that one staying legal, but I never did it, because it just doesnīt sound like a good idea to me.
A limit is a limit and therefore mandatory; quite a no-brainer.

For the destination, destination alternates and enroute alternates you can disregards the gusts, thus just consider the main windspeed. For ETOPS enroute alternates you HAVE to stick to the gusts according JAR-OPS.

Remember that the METARs and TAFs give you true winds, whereas the RWY designation magnetic (sometimes makes the crucial difference!).

Even though the wording is "SHOULD be within limits", my understanding is, when the OM-B denotes a mandatory limit for the XWC that is ecxeeded by the mean wind in the forecast, I consider it closed for planning purposes (though it may be legal to do it).

There are other examples of things that JAR-OPS allows you that just donīt make sense to me (e.g. "adequate" vs "suitable").

Doing flight planning I always tried to stay on the conservative side rather than just exploring the edges of the legal frame.

Iīm just wrinting this out of memory, hope it helps anyway.
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Old 7th Apr 2008, 16:27
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Thank you Avionero, that's helpful.

What concerns me about comparing METARs with crosswind limits is the tolerance on wind direction -- variations of +/- 30 degrees don't even get a mention in the METAR, but it can make a big difference to the crosswind component. Where there's a xxxVxxx group, do you take the worst case, or do you ignore the directional variation and just use the mean?

Example:

METAR GCLA 061600Z 23025G40KT 170V280 7000 -DZ FEW025 SCT045 BKN180 23/10 Q1003=

What's the relevant crosswind on runway 19 at La Palma (centreline about 180 true, I think)?
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Old 7th Apr 2008, 18:29
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For my company the planning minima has to have the mean steady wind within limits, and gust factors can be ignored.

It doesn't mean you can't go if it's outside the limit, but you need to have the alternates backed up.

[However if it's Jersey's 45kt crosswind, you'd probably not bother!!]
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Old 7th Apr 2008, 18:38
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Thanks for that Civil Pilot.

For my company the planning minima has to have the mean steady wind within limits
When you say "within limits" is that a wind speed limit or is that a crosswind component limit? If crosswind, calculated using the mean direction reported, or the worst case in the variation?
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Old 8th Apr 2008, 10:53
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Never heard of a legal limit for wind speed in absolute terms. The only planning limit that Iīm familiar with is the cross wind COMPONENT. So if the mean wind is say 60kts perfectly aligned with the RWY centreline, you can plan it that way, since the COMPONENT is 0.

Gusts only have to be considered for ETOPS alternates as far as I remember, for everything else you just have to consider the mean wind.

Iīm not 100% sure right now, but I think in the example given by bookworm, you can also stick to the mean wind.

As with the other minima, you can depart when the destination doesnīt fulfill the minima as long as you plan it closed (-> 2 alternates).
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Old 8th Apr 2008, 11:45
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X/wind component.
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Old 8th Apr 2008, 20:23
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Never heard of a legal limit for wind speed in absolute terms
All A/C I have flown have had a max wind for Taxi limit. Little point in battling the A/C onto the deck with max crosswind limit only to not be able to taxi to stand.

Other than that we operate as per AVCP, although our Ops manual makes no reference to wind speeds when planning which surprises me.


Example:

METAR GCLA 061600Z 23025G40KT 170V280 7000 -DZ FEW025 SCT045 BKN180 23/10 Q1003=

What's the relevant crosswind on runway 19 at La Palma (centreline about 180 true, I think)?

Can't help with the actual legal view on this but I'd assume (for planning purposes) worst case 40kts from 270, ie all crosswind, especially as wind veers in gusts... which for my A/C means steady wind near limit and gusts out of limits. Now according to JAR thats OK but I personally would be looking to have a more usable alternate or 2 up my sleeve and plan and fuel accordingly.

Last edited by Orp Tolip; 8th Apr 2008 at 20:44.
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Old 9th Apr 2008, 06:57
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Thanks folks, this is all useful. Please keep 'em coming.

The the consensus seems to be that some Ops Manuals specify crosswind components for planning purposes, but that the wind direction used is the mean direction in the METAR (and presumably TAF) rather than worst case, and (ETOPS excepted) gusts are disregarded.
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Old 9th Apr 2008, 08:50
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Probably your own judgement might be more restrictive than the manual sometimes.
You can stick to the mean wind direction and speed, disregarding gusts; so assuming the Palma example with a max crosswind component of 30kts, you would be legal.
You eventually want to compose a flight plan that makes sense to the crew and not only to the lawyers. So if you feel a landing at destination is not assured (due to the wind), feel free to add a 2nd ALTN, extra fuel, whatever can help them just in case.
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Old 23rd Sep 2011, 10:46
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Bookworm,

I have only just fond this post however late. Please refer to the table in JAR OPS 1, Subpart D 1.297 "Application of Aerodrome forecasts (TAF's & Trends) To pre-flight planning"

This specifies when you should take wind limits into account and also when mean or gust is applicable i.e. Destination, Alternate, Enroute Alternate and ETOPS only etc for pre-flight planning purposes. of course a healthy dose of common sense will always keep you safest.

Regards
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Old 23rd Sep 2011, 19:21
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Bookworm, that's common sense:
OPERATIONAL PRACTICES FOR INTERPRETATION OF METEOROLOGICAL INFORMATION
For planning purposes an aerodrome shall be considered to be below minimum if:
The RVR or meteorological visibility is below the applicable minima (precision approach)
The ceiling or vertical visibility is below the applicable decision height or minimum descent height (non-precision approach / or circling only)
The steady crosswind component exceeds the prescribed limitation for the aeroplane type. The steady (mean) wind should be used and the gusts may be disregarded.
The head wind or tail wind component exceeds the prescribed limitation for the aeroplane type.

The EU OPS however doesn't specify application of wind for the destination only for alternates. Bear in mind that wind directions given in METAR or TAF are true directions to the nearest 10 degrees within the last 10 minutes.
In other words you can always depart regardless of the wind forecast at destination having alternate within the limits.
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