Cross Wind Component

[smith]

As a PPL, I always think it would be easier if ATIS and tower broadcast Crosswind Component instead od surface windspeed as it would make life a hell of a lot easier for us especially as approaching an airfield ATIS gave us runway in use and crosswind component. And on clearance to land the controller would say "G-XXXX crosswin component 12kts RW31 cleared to land."

Would cut out a bit of workload and would tell us immediately if it was safe to land. When given w/v we have to work out angle off the runway then xwind component then decide whether it is safe to land, which I don't usually do when I am about 1 minute from touch down.

[Dave Gittins]

One to think about.

My instinctive reaction is just give me the raw data and I am quite capable of translating that if I am on RWY 26 and the wind is 230 at 10 it isn't a problem. Plus I have a "gross error check" from the windsock which'll be pointing 30 degrees across the runway and hanging at 30-45 degrees from the vertical (dependent on it's calibrated speed).

If it was a wind of 180 at 20, I would have known long before I got to a "cleared to land, surface wind .... " situation that I was going to have some fun (if not being outside the demonstrated limits for the aeroplane) and anyway I would know how the aeroplane felt and what control inputs I was using to keep tracking the C/L.

On balance I think I prefer thing just as they are.

DGG

[spekesoftly]

You could try asking ATC for the crosswind component, when appropriate; it is available on some displays.

[Keygrip]

Are you then going to ask them for the headwind component (so that you can calculate the landing distance required); ask them for the tailwind component (so that you can elect to land downwind if conditions dictated that you could).............and then ask them for the actual wind conditions in order to calculate if it would be safe to taxi the aircraft after landing.

There are numerous reasons for requiring the effects of wind - so get the actual conditions (which they give you now) and then work out which bit is relevant to you.

I'm sure somebody else will advise - crosswind component can be taken as a "percentage" of the actual wind. The percentage is derived from "what's the angular difference between the actual wind and the runway direction".

Say, runway 36 and wind 360 @ 10 - angular difference zero - so zero crosswind.

Runway 36, wind 030 @ 10 - difference 30°. Take the difference (30) as a PERCENTAGE of 60 (the number of minutes on your wristwatch face [assuming an analogue watch [good for pilots]]).

The percentage is 50 - so 50% of the total wind strength is the crosswind component....in this case 5knots.

Runway 36, wind 020 @ 10. 20° difference - %age of 60 = 1/3 (or, point three). 1/3 of 10 - near enough 3knots.

Runway 36, wind 040 @ 10 = 40° difference. Percentage of watch = 2/3 (.6) so crosswind is 6knots (ish).

Wind 360 @ 40. No crosswind - but wouldn't land a Cessna 150 or PA28 (except in an emergency).

[Preston Watson]

Having the wind component can tell a lot of things.

Some of which are:

Tailwind factor - If the speed is more than 5kts it can considerably increase the landing distance required. This is essential on a limited length strip.

Gross Error check - Ok you've got the ATIS and the runway in use, does the wind look correct for the runway you have obtained from the ATIS? If not you can request the runway be changed (in the quieter airports, not Heathrow).

Gust factor - Important to know, if there is more than 50% gust factor than the stable wind strength, wind shear could occur.

Circuit pattern - So what way is the wind coming from, what way do you apply drift to keep a circuit pattern. E.g. If the wind is behind you as you turn base then you should begin the turn earlier, if it is in front of you then you can turn in later to line up on finals.

Upper wind check - If the wind on the ground is more than 90 degrees different from say the 2000ft wind then you can expect windshear, turbulence.

Best way to do it is set the CDI bar on the HSI to the runway heading, and 'bug' the wind if possible, or look at where the wind is from in relation to the runway.

If the wind is 30 degrees off the runway heading then .5 times wind speed give x-wind strength on landing with say a VREF 60kts
45 degrees .75 x-wind
60 degrees and above take the full wind strength as x-wind strength

When you do IFR flying you need the wind as well to apply drift in the approach and to time the approach and hold if required.

There is a lot of information from the wind, x-wind is just part of that.

It comes quickly enough after a while; working it out in your head and giving an estimate within 1kt or 2 x-wind is good enough.

Good luck :ok:

[Gonzo]

does the wind look correct for the runway you have obtained from the ATIS? If not you can request the runway be changed (in the quieter airports, not Heathrow).

You can still request a runway change!:ok:

[No_Speed_Restriction]

if you cant perform simple maths on the approach then you must be maxxed out!

[SID East]

The clock or watch face works well for me.

As ATCO with PPL I tend to give the cross wind component when I think it is particularly relevant (strong gust, light aircraft who might be susceptible or formation departures etc.) however, they always get the actual surface wind. Sometimes you can see an ac struggling to track the centreline on approach and a quick "heads up" of the actual cross wind component does not hurt as workload can be quite high for them at that point.

Also 1/2 the crosswind component is the heading correction needed into wind for a Hawk on TalkDown (generally speaking) I use this as my reference for the first one of the day. Slower aircraft more correction, faster - less.

Triangles of velocities - good in the cool of the classroom
Rules of thumb - better for the heat of the cockpit methinks

Oh Well.


SID

PS Crosswind broadcast also standard for Simulated Assymetric, and Single Engined Multi Engine aircraft in my experience.

[Chilli Monster]

Most civil airports, unlike the military, don't have crosswind resolvers - so that's why you're not going to get given it.

The rules of thumbs explained here are easy to use and can be calculated in seconds - it doesn't have to be acurate, just the safe side of approximate.

One thing though - if you're that concerned why didn't you plan for this before take-off. Runway directions are published, winds are available. If you're that concerned about the crosswind either go somewhere else with an into wind runway or don't get airborne in the first place. Planning is everything - and part of that is having options. Wind data isn't just given to you when you're on short final, and there's lots of ways of getting it before hand.

[smith]

Thats the beautiful thing about wx, it doesn't always do what it says on the tin. I haven't ever had a problem with any crosswind landings, but being a low houred PPL, I just thought that an ATC announcement of crosswind component would take a factor out of the equation during a heavy work load period. No doubt with many hours of experience my rules of thumb will become second nature to me.

PS Why do so many people get narky and sarcastic on pprune?

[Chilli Monster]

See line one - you're not going to get it because we can't give it. It's NOT available data.

[spekesoftly]

A number of UK Civil Airports are equipped with the Vaisala Anemometer display - it is normally set to show 'Max' and 'Min' wind speeds in the top L/H and R/H windows, but these can easily be toggled to show the crosswind and tailwind components.

[Carnage Matey!]

If you can't calculate a gross estimate of the x-wind component from the raw data then you shouldn't be alone in an aircraft! Even as a 'low hours PPL' you've got 40+ hours and should be able to do the maths by now. I suggest you sit in working out x-wind components for an hour until you can do it quickly and easily. 30 degrees off - use half the wind. 60 degrees off - use all the wind. Getting close to limits - do some harder maths. Lets not change international aviation standards because somebody can't be bothered with maths.

[N5528P]

I do not consider that a good idea.

First of all, you should listen to instructions issued to the aircraft ahead of you to have a general picture of the situation, ATIS may also be a source, although sometimes rather old I admit. Checking the wind when receiving the landing clearance is rather late...

Providing the crosswind component does not make sense if you have different runways (two components for each runway, ATIS gets longer and longer, more confusion...). Even more, you do not have to make an exact caculation, if you are not close to your limit, since wind direction changes every second anyway.

Bernhard

[DRJAD]

I agree with the consensus: no problem with the current system.

It's unambiguous, keeps ATIS and landing clearances short. One can plan beforehand for the likely scenario, and calculations and visualisations are easy in flight using simple trigonometric estimations - as Chilli says, keeping on the safe side of approximate.

[Cough]

Comparing the actual wind with FMC displayed wind on commercial airliners gives you a massive clue what you are going to have do with the thrust levers on final approach... Leave well alone...

[fixa24]

Here down under, we are required to give the xw component if it is greater than 8knots for a single engined aircraft, greater than 10knots for a military aircraft, or greater than 12knots for a civil multi engined aircraft.
Although we do have the digital displays which give us headwind(and tailwind, depending on which runway is selected) and crosswind readouts. We also have to give the wind to any internantional operatoralong with landing clearance.:ok:

[ATCOJ30]

Whatever happened to basic airmanship? Surely that falls within its terms of reference? It certainly did when I did my PPL anyway. I can only hope you can cope if eventually you fly to/from a strip where there's no one telling you the wind on the RT and you maybe have to look at a windsock or for other clues (eg smoke drift)

And do you really think it's an ATCOs job to tell you if you are "safe to land" (quote) your aircraft in a crosswind, when a) we have no idea what experience/ability you have as a pilot b) we do not know the cross wind limits of the aircraft you are flying.

[youngskywalker]

Crikey fellas, the chap only asked a question!! I was told when learning to fly that there is no such thing a a silly question! That's what happens when you ask Gods gift to aviation, ATCO's! (hehe no offence intended) :O

Personally I am happy enough with making the calculation, all I really want to know from the crosswind is: is it within the aircrafts limits and mine! telling me the exact numbers constantly down the approach doesnt help me in the slightest, except maybe if your flying a jet when thrust settings are more critical.

As ever just my take on it...

[VRB03KT CAVOK]

Check the windsock as you are passing through 300' AGL. I'm sure I'll be corrected if I'm wrong but the type of windsock used at an uncontrolled aerodromes needs 25kts to reach horizontal and about 15kts to get halfway there.

As fixa24 said, in Oz it's on the ATIS.

If the crosswind on the ATIS states that the gust factor is beyond the aircraft's max crosswind my company proceedures are to ask the tower for a 'crosswind check' on finals.

That way if something goes wrong on the landing it's on the tape and the insurance company can't say that we were operating outside the aircraft's capabilities!

[dontdoit]

Right, this is how we do it in the jet:

Between 60 deg and 90 deg off = full crosswind

60 deg off = 4/5 of windspeed (4...5...6)

50 deg off = 3/4 of windspeed (3...4...5)

40 deg off = 2/3 of windspeed (2...3...4)

30 deg off = 1/2 of windspeed (1...2...3)

Less than 30 deg off = negligible crosswind

Which saves massive mental gymnastics at 200 feet, etc!

[strafer]

Here's an easy way to work out your xwind component. (No diagrams here, so bear with me).

Set your DI to the runway in question, eg 36. Draw an imaginary line from the 9 o'clock to 3 o'clock positions. A wind from 090 will in this case have a component of 100%. Now say the actual wind give by ATC is 20 knots from 040. Look at 040 on the DI, this will immediately give you a idea of where the wind is coming from and which way it's trying to 'push' your 'plane. Now draw another imaginary line down from 040 to the imaginary horizontal line. In this example it will meet about 1/2 way along the line. 1/2 = 50%. 50% of 20 = 10. Your xwind component is therefore 10 knots (which is close enough to the actual value as to make no real difference).

Easily done in seconds, leaving you enough time to realise you've forgotten to put the gear down.

[drb757]

It is not rocket science. The problem is if you ask a british pilot how to do it it is sort of like asking him what time it is and he will proceed to tell you how to build the clock

[Timothy]

(No diagrams here, so bear with me).Happy to oblige:

http://www.artifax.net/misc/wind.jpg