Coping with significant crosswind

[Jabiru Phil]

Oldest trick in the book:

 

Just look at your compass rose, HSI, EHSI or what type of instrument you're flying the approach on. In most cases it has a inboundcourse coinciding to the relevant runway track set to it.

 

- Put a finger on the number relating to the reported wind.

 

- Trace a line parallell and perpendicular to the inboundcourse on the instrument.

 

- Note where the parallell line intersects the inbound course and where the perpendicular line intersects with the deviation dots.

 

It makes it very easy to see what percentage of the wind you have coming in from the side and the nose/tail component. Just multiply that with the windspeed and you're home free.

 

/LnS

 

Got this from another site

 

 

[motzartmerv]

Far out... And here I am looking at the windsock......

 

 

[Jabiru Phil]

At 60 kt it's about 1 kt per degree.

 

Thanks Zibi.

 

Thats the information I was looking for.

 

Cheers.

 

 

[Jabiru Phil]

A wind sock knows not the difference between 15 or 30 knots IMO:drive:

 

 

[motzartmerv]

True..

 

 

[motzartmerv]

Thats a usable rule.. Thanx for sharing. Its similar to one used in IFR track correction on NDB's but ive not seen it used as above.

 

Don't forget that the wind strength will decrease as you get lower aswel, so if its on the limit at 500 ft chances are good it will be ok on the ground.

 

cheers

 

 

[turboplanner]

Ok I stand corrected then, good work!

 

Now all I need to make my day is a formula which calculates the kerb to kerb turning circle of a truck from wheel cut angle and produces an accurate result.

 

So far three manufacturers are using three methods which all come out differently.

 

 

[facthunter]

When you are going really sideways on approach, you know you are going to have a job to do. You get to know your plane. The crosswind usually reduces near the ground, which can help. A tailwheeler may land ok but groundloop when the forward speed drops off a bit due to lack of rudder effectiveness. A well set-up tailwheel that responds to pedal position well will aid there, and you have to keep the stick right back at the slower speeds to keep it on the ground, but you don't taxi downwind with it in that position. Nev

 

 

[dazza 38]

When you are going really sideways on approach, you know you are going to have a job to do. You get to know your plane. The crosswind usually reduces near the ground, which can help. A tailwheeler may land ok but groundloop when the forward speed drops off a bit due to lack of rudder effectiveness. A well set-up tailwheel that responds to pedal position well will aid there, and you have to keep the stick right back at the slower speeds to keep it on the ground, but you don't taxi downwind with it in that position. Nev

Why are people always going side ways? They should be going down final tracking down the centre line with the into the wind wing down counteracting drift. Flairing and touching down on the into the wind wheel first. If they are not doing this.They have been taught x winds incorrectly.If the x wind is a biggy they should be doing a combination of the above and a bit of the side ways approach yawing into the wind .Then the kicking it straight on final.If they cant do that.They shouldnt be flying.Just sayin

 

 

[facthunter]

Some aeroplanes will draw air on approach in the fuel system if a prolonged sideslip is done. A combination is OK sometimes but passengers would not like a sideslipping approach and some planes don't accept it as a technique with flaps extended in the POH. Nev

 

 

[motzartmerv]

Either method is acceptable dazza. The forward slip technique is loosing favor among schools these days, most preferring the crab method. The reasons for this are a can of worms that would probably require a new thread.

 

 

[dazza 38]

Hi Nev, I should have mentioned that.More that one plane has starved of fuel on final when the fuel pick up has sucked in air when the higher wing has had its fuel tank selected.

 

 

[dazza 38]

I just get worried about the side loads put on undercarrages. Generaly U/c legs are not realy designed for side loads.They are to a certain extend but they do get stressed. Also I guess the crab only method is easier for pilots to learn and keep current in. Also as Nev has mentioned, it is embarrasing if a pilot flying a a/c where their may have Left/right tank selection and they have the higher down wind wing selected and the fuel pick up sucks in air. Or more likely with the majority of fuel systems, the lower wing fuel pick up sucks air.(Most a/c have dihedral so the fuel pick ups are in or near the wing root).I hope that pilots know their aircrafts fuel system .

 

 

[David Isaac]

David. I understand your views and I know that they come from substantial experience, but I hope I can offer a contra view without you wanting to have me shot. Lol.

Motz I would always welcome an alternate view, it is the best way to learn … I don’t have a rifle or a shooters license anymore so you are safe buddy … besides, if I shot you I would miss you … LOL.It is a constant challenge to qualify what we are trying to say in a post and keep it in context.

 

The problem I have with the cross runway takeoff ( I'm only talking about takeoff, not landing) is as follows.I realize that an angle across the strip in a STOL aircraft would change the xwind/ headwind components. We have 2 bantams online with our school, and I could argue that they are as STOL as it gets. If the wind conditions present on the day were such that I had to tell a student or a pilot to cross the strip and aim for the edge of the runway 100 meters ahead, I would be mad. If the conditions were such then the bantams would remain hangard. I could just see myself in court attempting to explain how I came to be recommending the procedure. Perhaps I have tainted view as our strip is narrow with cattle fences close to the strip.

I totally agree with you and would never advocate this method as part of the initial pilot certificate training; I would consider this advanced student training only in the right type of aircraft at an appropriate strip; or advice for experienced pilots in appropriate aircraft. Most lightweight U/L aircraft would struggle with control in gusting conditions and if it were substantial gusting conditions I may not even attempt it. Although gusting head wind component is easier to manage than gusting side winds. Strong winds always need special consideration, gusting strong winds need extra consideration. I am not so much advocating this approach in gusting conditions, I am attempting to express and option for a STOL type aircraft where the cross wind handling limits would mean that takeoff in a reasonably stable stiff breeze could be better achieved using an angle technique with a better handling outcome.

 

What if the pilot thinks to aim at the side of the runway 100 meters along, but infact needed 120 meters? What then? Does he boot the rudder and turn with the wind to align with the runway? Secondary effects are strong at low speed so up comes the windward wing.

In that case the pilot seriously miscalculated and should not have been there in the first place. In that example it is too high a risk and I would not take off in those dimensions. The pilot has to take responsibility; there would be plenty of examples where you would NOT do it and plenty where it would be safe to do so.

What if the engine fails just after liftoff? The aeroplane is not within the splay of the runway? Land straight ahead into what?What if the takeoff is dodgy and a settling back onto the ground occurs? How many times have we all seen that happen?

I agree, a proper assessment is always required, doing this technique at marginal airfields with marginal splays is something I would not do, but in an open class 3C with plenty of splays like Kaz did is minimal risk. But in any engine failure I would rather glide into a strong headwind in any case because my ground speed on touch down would be minimal in the same sense that my take off run would be shorter. The engine failure on takeoff is a risk in any case and there are plenty of runways out there where there is no where to go on the runway alignment, take Wedderburn for example or for that matter even Warnervale, just trees and swamp.

 

If winds were strong enough to need this procedure one could expect turbulence. In a light aeroplane which is much more under the influenc of wind gusts etc, room to move is a valuable lifesaving commodity.There are rules regarding a pilot assessing a potential landing/ takeoff area. He must calculate splay areas, toda etc. Someone using the technique in question is essentially using a NEW runway and by law would be expected to assess the area for hazards etc. These questions would be asked by the courts should I ever send a pilot or student out to perform this move an he/ she ends up injured or worse.

Absolutely, it is always the pilot’s responsibility under any conditions to assess the risks, including the marginal use of one way strips which many U/L pilots use. If he can take off at an angle and still meet the ALA performance dimensions for the particular aircraft then there is no issue.

I'm sorry I've gone on a bit here. But to simplify my point, if the winds were such that a STOL acft needed to do it, then perhaps discretion would be the better part of valor.

Not sure that your use of the term “that a STOL aircraft was needed to do it” is logical. I am suggesting that STOL aircraft are the only ones that could safely use this method because they would be the only ones that could meet the ALA dimensional requirements using this method at an appropriate runway with good lateral splay clearances.EDIT 11/07: Some clarifications and grammar corrections

 

 

[kaz3g]

This thread, together with one other discussion on the site prompted me to reach for my copy of Cliff Tait's "Water Under my Wings"...45 degrees will be 70% for headwind, and the crosswind will be 70% of the wind strength."

Yep... 70% of 30 knots = 20 knots approx

 

Stall full flaps = 28 knots

 

Result is a very short ground roll after a very slow approach.

 

Kaz

 

Kaz

 

 

[naremman]

I think you are making some valid points here, from a big picture perspective.Many of the airstrips I've seen posted on here are in fact very narrow, some with power lines over them, some with close tree lines, and a few you could only describe as one way strips being used both ways.

That is another aspect that has passed without commentary Turbz. A steady, consistent crosswind, evenly blowing over an open space is one thing, mechanical turbulence created by timber, buildings or terrain just makes it a bit more difficult proposition.

 

Our town strip is a beauty. Trees on both sides, a one degree overall slope and a crosstrip that funnels the prevailing summer breeze to exactly the point where you flare for the preferred runway. We have about 30 RFDS flights a year come through and I have even seen RFDS pilots in PC-12s caught out. Coupled with with some lusty wind shears at either end it is not a strip you ever treat lightly.

 

I always enjoy observing operations at Northam, just east of Perth, and the challenges that it presents. Jandakot based pilots who are having an initial introduction to a country airstrip find that this one is not always that welcoming, not that it is a bad strip, just a bit different.

 

Just when we think we have this flying lurk licked, there is always something around the corner to remind us how tenuous our mastery of this skill is!

 

 

[motzartmerv]

David, Thanx for the detailed reply..I knew id get you talking eventually. I appreciate you spending the time to quantify your views.

 

Its clearer to me now.

 

I am probably a little anal when it comes to 'non normal' operations. My old chief always drummed into me this credo: "always imagine having to explain your choice, decision or advice to a coroner" with regards to training. I know its a little dark, but it certainly keeps me thinking.

 

The engine failure on takeoff is a risk in any case and there are plenty of runways out there where there is no where to go on the runway alignment, take Wedderburn for example or for that matter even Warnervale, just trees and swamp..

I agree, but there is 800 meters in the runway direction at wedderburn before the trees, but crossing the strip would see you over trees in less than 100. ;) Just pointing that example out, im sure you wouldn't suggest trying it there.

 

cheers, and thanx again

 

 

[motzartmerv]

Not sure that your use of the term “that a STOL aircraft was needed to do it” is logical.

One more thing.. The reason its not logical is because thats not what I said..You added the word "was" to the term.

 

I didnt mean that a STOL 'was' needed, rather that a STOL acft needed to perform the technique to get airborne.

 

Cheers

 

 

[djpacro]

You can say that again, motzartmerv

 

 

[David Isaac]

Just pointing that example out, im sure you wouldn't suggest trying it there.

You are right ... Wedderburn is definitely out for that technique Motz, just imagine the turbulence off those bloody trees in any stiff wind ...

[motzartmerv]

Lol. Don't have to imagine... Is a mongrel of a strip on the wrong day.. Actually the last time I flew there was not a good day.. Compounded by the fact that the ctsw I was instructing in had a major flap failure just over the trees and decided to go to full flap. Lol, an interesting few seconds while I diagnosed and fixed the problem... Not nice!!!!

 

 

[kaz3g]

I read somewhere a while ago about a method of determining X wind strength on final.It went something like... 10 deg off centre line = 10 kn X wind.

Does anybody remember the formular?

 

Phil.

Use the 1:60 rule!

 

Most of you fly final at around 60 knots. If you have to hold 10 degrees into wind to fly the approach you have a 10 knot x-wind

 

Kaz

 

 

[djpacro]

Generally, that is not true, kaz, and I'm not referring to the 1:60 rule but your application of it.

 

Doesn't matter to me as I can't determine the angle anyway.

 

 

[boingk]

I dont understand the arguement - you should be flying as you need to, not flying as numbers in your head say you should.

 

Surely a pilot is more concerned about landing safely and holding the craft in the right attitude on descent, for the conditions, than what they think they ought to be doing based on an arbitrary number? The angle and power you need to hold in the crosswind is the main thing - disregard everything else.

 

Either I'm missing the point or this is a storm in a teacup.

 

- boingk

 

 

[rgmwa]

I think I've got it! If the runway is sliding to the left I have to move further left, if it's sliding to the right I have to move more to the right. If it's not moving either left or right, then so far so good.

 

rgmwa