Using a wind component chart on final
 

Hello all,

This is my first PPRuNe post!

I am currently doing my PPL part time while working. I'm at the stage where I have completed about an hours worth of solo time.

Prior to flying circuits, my instructor taught me how to calculate the crosswind component using the clock method. I saw that you could also use the sin values. Both methods I understand, however, on final, my brain can't do the maths that quickly in addition to flying the plane and getting set up for a decent landing!

Is it frowned upon to have the wind component chart at the ready to find out the crosswind component for landing? :-s

Thanks in advance! :ok:

That probably depends on who you ask. But on finals with a crosswind landing ahead there are more important things to do than look up the exact value of the crosswind component from a chart. The wind speed and direction they give you are only approximat values anyway, so what's the point of deriving "exact" values from them using charts (or even worse: a calculator or smartphone app - yes those exist as well...)? Listen to your instructor I would say and estimate it using some rule of thumb!

Be aware of it, nothing more.

Strong from the right, weak from the left etc. That'll do you...

Aviation requires mental arithmetic skills. There will be those on the new fangled magenta line a/c, even worse the FBW brigade who will disagree. Any answers are always in the i-pad, FMC or Japanese brain in their flight bag. However, they have forgotten the most basic rule that the best computer on the a/c is between your ears; or it should be. A big shiny jet does not negate basic physics & arithmetic. In jets there are moments where legal limits come into force and need an instant decision. X-winds & tail winds are one of them, fuel flow & endurance in non-normal config another. And god forbid those guys who do load sheets on a calculator and still get it wrong.
In PPL light a/c flying there are many more scenarios, perhaps. 1 in 60 rule can be applied in many useful ways. Drift angles in holding patterns; wind vectors on finals another. I came from an era where mental maths was the norm and we kept it alive and well all through university. At flight school I'd become rusty and it was a hindrance. The excellent local pub had a dart board and that was the most enjoyable saving grace for removing the stress of VFR navigation calculations.
For wind vectors I always use 00 30 45 60 90. Headwinds are 100% .9.7.5.0. The x-wind is reversed starting with 100% at 90 degrees. It's easy. Throw away the calculator and engage the dormant grey cells.

Ok, there should be a windsock somewhere. Just take a look and see which way it is pointing relative to the runway, and if it is stable or lifting up and down. If it is moving a lot and at 90 degrees to the runway, and you are having to crab such that you are looking at the runway through the window at the side, then that is enough crosswind to land on a more into wind runway, or another airport.


No maths required.

Remember, you have two things to consider, direction and strength. Light wind at 90 degrees, no problem. Strong or gusting wind, you will have windshear to consider as well, and possibly difficulty taxi-ing. So that is why you calculate crosswind component WHEN PLANNING THE FLIGHT.

Not during the approach. You should leave the ground with a forecast that shows you landing where conditions are within your capabilities. Plan B comes into play when things change, weather forecasts aren't 100% after all.

On the approach it's all about sight picture and (dare I say this) feeling. Set up your approach at a comfortable height, flaps configured for landing, trimmed for the airspeed you have previously calculated. Use flight manual figures please. Make due allowance for gusts.

Then look at what is happening outside, as well as inside.

If the crab angle (or wing down, if you do it that way) is reasonable, and you are staying lined up with the runway, then carry on with an approach, with the mindset that you will be going around, and might convert to a landing if all goes perfectly. This way you get to see exactly what is happening before committing to a landing.

If you do this and are unhappy with the approach, you can always have another go. If it still isn't looking good, a different runway or diversion may be in order. You can always ask for a more suitable runway if you, the Captain, consider that is what you need.

As you gain experience you will be able to cope with more demanding conditions.

Practice with your instructor if you feel you are outside your comfort zone when flying solo.

If you do decide to land, fly the aircraft until it stops.
If you are flying a tailwheel type, fly the aircraft until it is tied down.

The one important point is to know which side to dip into the crosswind. All the rest must come from your symbiose with the aeroplane - it will tell you what it needs, though some have a gentler expression than others.

[[ edit: typed at the same time as @Piper.Classique - as usual, there's not much to add to her words. I particularly like the "carry on with an approach, with the mindset that you will be going around, and might convert to a landing if all goes perfectly"]]

The time for using a calculator is well before entering the zone.

On final the wind will be changing on descent. The airplane will be telling you if there's too much x wind (although in a glider you likely don't have the choice of going to another airfield).

Trees, terrain and hangars upwind of the runway can have major influence on the wind.

I recall a Bob Stevens cartoon about a pilot with several different calculators for every conceivable phase of flight. The Salvage Value calculator was put in use at the end of that flight.

Keep it simple. Figure out the difference between the wind and the runway heading, e.g. if you're on 31 and the wind is 330, it's 20 degrees. If it's 60 or less, divideit by 60, e.g. for 20 degrees it's 1/3. And multiply that by the wind strength, e.g. if it's 15 knots, you have a 5 knot crosswind component. This is easy to do in your head, and is at least as accurate as the information you're being given in the first place. If the difference is more than 60, take the wind strength as the crosswind.

Details... the error is never more than 14% (at 60°). The wind direction and strength are less accurate than that. You don't need an accurate number - what are you going to do with it? The only reason you need to know anything at all is to know whether you even want to try the landing. So if the wind strength is less than your crosswind limit (set by you, the aircraft, or your school), it's of no importance. If you're trying to land in a 40 knot wind it does matter, but that doesn't happen often and you'd better be prepared to go around at every 10th of a second.

Of course for a written exam they want the answer to the nearest 100th of a knot, and for that you do need some kind of chart or calculator. But don't confuse what happens in a written exam with actual flying.

Jan, that is most gracious of you. But you put it so much more gently, and in fewer words.
Frannibal, welcome to pprune

Here's the easy way (as per RAT 5). Remember three numbers. Point 5, 7 & 9. With a wind 30 degrees off the runway, the crosswind component is 0.5. At 45 degrees it is 0.7. You can already guess what it is for 60 degrees. The same applies for headwind/tailwind components. These values are also good enough for cross country planning.

PM

Get your instructor to show you how to use the VOR to estimate cross-wind component - it's accurate and simple - also, at a glance, you have an indication of head or (hopefully not) tail wind component.

OC619

how to use the WHAT? 20th century technology? Available at +/- 1% of aerodromes?

(sorry, couldn't resist)

Blimey. Just look at the windsock. You really don't need to know numbers.

[QUOTE=bose-x;9840772]Blimey. Just look at the windsock. You really don't need to know numbers.[/QUOTE

It is a good idea to use a simple system 30/45/60 degrees from the early days so that when you need to assess the crosswind in IMC it is second nature. It's is actually very easy.
Look at your watch 30 degrees = 30 minutes= half an hour...half the wind is cross wind.
45 degrees is 3/4 of an hour = 3/4 of the wind is cross wind
60 degrees is a full hour...all crosswind.

I don't look at the windsock on short final. I just sideslip to keep the aircraft pointing along the runway, and staying in the centre of it.
And get one wheel on the runway.

It is helpful to be able to assess the wind vector well in advance of venturing into the vicinity of a runway where there maybe a windsock in sight. I challenge you to find a windsock near the threshold of a major airfield. there is one somewhere, but try finding it visually as you wrestle your guided ping-pong ball down finals. Before you set out you can decode the METAR/TAF and when approaching the airfield the tower will give you the recorded wind. You need to be able to decide quickly if you are going to continue. If it is close to limits, and you do continue, you need confirmation on short finals to be 'comfortable'. What is wrong with expecting pilots to do some mental gymnastics? It should be par for the course.

To answer the original question, you won't want to be looking at charts on final, you'll be fully occupied with flying the aircraft.

As you fly down the extended centreline it will be obvious whether you're crabbing to the left or to the right ... indeed after not very much more experience than you already have it will have been obvious whether flying down base leg has taken a longer or shorter time than usual, and it will be obvious whether you've struggled to make the extended centreline (headwind) or whether you've overshot it (tailwind).

Any or all of which tells you the direction the crosswind is coming from, even if you didn't do any homework before take-off and didn't remember what happened at take-off and didn't look at the windsock whilst downwind.

So there are two things left that you care about: whether you can land safely, and whether you can land legally (aircraft limits, club rules, whatever). And at your stage you're almost certain to form the judgement that you don't like it, and that you're therefore going to go around, long before "legally" becomes an issue.

One day "legally" will become an issue - say you're happy landing with an 18kt crosswind, 'cos you've done it dual, but the club limit for solo is 15kt - and you'll then want to be able to do the arithmetic. If you can't do "one sixth of the wind speed per ten degrees off runway heading" in your head there are other parts of the course you'll struggle more with.

Thanks for all the suggestions!
 

Hello everyone, thank you all for your replies and suggestions :-).

To be honest, in all this time, I have never seen the windsock on final! I am trying too much to focus on landing rather than look elsewhere other than the runway. Next lesson I will make an effort to look for it! :-D

I do check the METAR every day even at work just to get my head into that different "language" and try to calculate the crosswind from that then check if I am correct. This helps...and it also helps that I am in the comfort of my desk haha.

I like the sound of keeping things simple by using the 30,45,60 rule, but for the exams I better practice the more accurate methods. I guess practice makes perfect. My limit is 17kts and fortunately (or unfortunately as it could be good practice) it has never really been close to the limit. I haven't really done any serious crabbing either...I think I will get a shock when I will have to haha.

Thanks again for all your replies. So helpful!

Fran :O

One other thing, often (not always) the wind at surface level is less than on your approach - so don't worry too much if it all seems a lot as you descend. There is a (good) chance that when you get to the tricky bit the wind has calmed somewhat.

Or, put another way, don't throw your approach away too early...

But don't be afraid to throw it away either, and at certain aerodromes - throwing it away early will save your life! If you're not dead on the speeds, straight along the centreline and your wanted glide path, and you are not confident you'll make it - there is absolutely no shame in going around.

I think the best thing you can do is use your watch method, and keep practising. ( [difference between runway and wind direction] divided by 60 ) times wind speed. 250/10 on runway 21 means 40 degrees difference. 40/60 is the same as 4/6 which is equal to 2/3. 2/3 of 10 is roughly 7kts and that is roughly your crosswind. You don't need to use exact figures... If it was 235/10 on runway 21, thats 25degrees difference, 25/60 is roughly 30/60 = half, so the crosswind will be slightly less than 5kts. Keep coming up with random numbers and random runway headings over breakfast, lunch, dinner, whilst watching TV...etc... and keep doing them whilst eating / watching TV until you feel confident with it. (the multi-tasking helps to make the figures easier when overloaded during flight).

With experience, although if you intend to go commercial, you will need to do them before every landing, you may not need to know the exact figure, just to be aware which side the crosswind is. 17kts is the "demonstrated crosswind limit" of the PA28, with experience and skill however, one's limit may differ from the book figure (providing insurance and club rules don't prevail of course).

Keep at it - they'll become second nature! That'll be really useful for your GFT (or whatever it is now called).

Good luck with your learning!

Just out of interest, how much effort are you putting into flying? Is the aircraft doing what you want? The reason I ask is that if you have been shown the magic numbers to make your life easier. Approaching the end of your downwind leg you select something like, but please don't quote me, 1,700 RPM, one click of flaps and TRIM. The aircraft should be flying itself, nicely decelerating to 65 kts or so. On base leg you should just be there looking at the view working out when to turn finals and possibly even looking for the windsock. Once on finals you will thinking about lowering more flap and reducing to approach speed. At the same time a good squizz outside should tell you if you are drifting to the left or right of the centreline. Correct as necessary. Wait. Correct etc. This is one if those times when less is more.

Best of luck.

PM

Here's what I do. As soon as I know what runway is in use, or is likely to be in use, I set that on a cockpit dial somewhere. Most aircraft I fly have at least an ADF and one VOR display, some have an RMI or something else. One of those gets adjusted so that the runway in use is on top.

As soon as I get a wind vector somehow, I can then just superimpose that mentally over the instrument, and I know immediately what sort of wind I'm dealing with.

As others have said, the exact value is not important. It fluctuates anyway. What is important is the direction it's coming from, and the approximate strength, plus any gust factor.

Don't try to overcomplicate things. Especially not when your brain and eyes should be engaged elsewhere.

I wouldn't be able to tell you what heading I had flown in a cross wind VFR approach. Eyes out of the cockpit nearly all the time except for occasional check of ASI.

Back to the VOR method - it has the benefit that you don't need to work out angle between wind and heading, you just look.

You can use the DI, ADF or VOR for this - the advantage of the VOR or ADF is that you can do it before you are on Final.

http://www.cfinotebook.net/graphics/...e-of-thumb.png

In this example (it's the only diagram I could quickly find):

• Runway heading 35
• Wind direction 040
• Reported wind 30 knots (little high - I know)
• Cross wind component - the blue arrow comes down around 2/3 of the way from centre to outside of the dial. 2/3 of 30 == 20 knots

The full discussion is at: Crosswind Approach & Landing

OC619

That should read "runway 35" or "runway heading 350" to make sense.

My apologies - comes of trying to post while not letting my manager see I'm not "working".

OC619

If we're going to be pedantic, runways don't have headings.

Ah, there's a new browser feature we need.


Once Upon A Time one wasted time in the office with Minesweeper, which like all good games at the time had a "boss button" - if you hit Escape the window minimised (on more sophisticated software the game would be replaced by a fake spreadsheet display).


Wot we need is a way for web sites to indicate to browsers whether they're real work or not, and the browser then to react to a boss button if a game (or PPRuNe or whatever) is being displayed.

Piper Classique, post 5, said all you need to know on this. And nothing you don't need to know.

Thank you all for your suggestions! I am currently practicing the following "rule of 6" i.e always dividing the wind by 6 then multiplying it with the difference in degrees:
e.g 10 degrees difference = 1
20 = 2
30 = 3 (in this case the crosswind will be half)
etc...

Runway in use: 27
Wind: 250 at 12kts

270-250 = 20 degrees difference
I then take wind speed and divide that by 6 so in this case it is 12/6=2
As there is 20 degrees difference, i do 2 * 2 = 4
The crosswind component is 4.

I have been told that this is a more complicated way of doing it, but it seems to suit me well for some reason! :-s

I understand the DI method, and maybe i can try this out next time i am flying. :)

Thanks all!

That's what I do. It looks more complicated written down than it seems in reality. I'd stick with it.

The big question is: Why do you have to know that when you're on final? Does it make any difference? No it doesn't. You fly the approach, and if you can keep it stable, you continue. If the crosswind exceeds your or planes capability, you go around. Simples.

One should develop a good visual cue of where the runway intercepts the aircrafts windshield to determine if things might be outside your own limits.
However, I always used the approach speed and angle difference on the DG to Rwy direction out of curiosity.

At 60 kts, a difference of 20degrees was roughly a 20 kt crosswind component (1 kt for every degree) .
At 120 kts, the component is half the angle (1 kt for every 2 degrees).
You don't need it exact but good for a rough guide.

Better to not think of it and just do rather than over thinking and getting worked up or worried about it.

Well it does in some places. For example, our ops manual gives the max demonstrated in the POH as a max crosswind (and please don't start a discussion about max demonstrated v crosswind limit as I'm sure we are all clear). If the crosswind is outside the POH figure, then our procedure is to divert to somewhere where there is a more into wind runway. So it really is necessary to be able to calculate the crosswind both when joining and when on final.

As for continue until the crosswind exceeds your or your aircraft's capabilities, that's a recipe for disaster. It's a bit late to discover your assessment of either's abilities was a bit optimistic as the undercarriage collapses due to a sideways load.

This will get you all squared away

https://wordery.com/mental-math-for-...SABEgLPPfD_BwE

https://wordery.com/mental-math-for-pilots-ronald-d-mcelroy-9781560275107?currency=GBP&gtrck=L0hpczdPb3o1R2hxWEZLajd3enJ VMUY1ODZUL05zV1d6SitzcXRCSDhFTjIzeThjbERBV21SNWxlcDBTTGM2aWN ldVQ2RlV3bmczSkE1bkNkUHRVN1E9PQ&gclid=EAIaIQobChMIqLrwjrnS1Q IVljLTCh3EwQwOEAQYASABEgLPPfD_BwE

You missed the point. You calculate that, on final? That was the key point in my post, on final you don't mess with anything apart from keeping the plane pointing the right direction. If you can't, you go around, it doesn't matter what numbers you came up with earlier.

You calculate crosswind on final and compare with any limits you have to obey, yes. Otherwise you might land (perfectly safely but) outside limits. How else can failing to break any such rules be achieved?


If the crosswind is one knot outside limits I ask for a "wind check" at intervals on final until I get one that's one knot inside limits, then I don't ask any more. Doesn't everyone do that?

But you know that limit before you turn final, don't you? So the actual math has been done.
In our opspecs we are not allowed to start an approach unless weather is inside our tolerances.

The limit, yes, but not the wind - that's passed with the "cleared to land" by which point I'm almost always on final.

Ah, local variations then. I am always given the wind on downwind (and again on final) giving me a bit more time to calculate or at least to raise a couple of eyebrows.