Coping with significant crosswind

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Coping with significant crosswind

 

During the initial stages of the ground roll in any type of take-off with a significant crosswind component, the aircraft will tend to weathercock into wind and pivot around the main wheels. There are lateral stresses on all wheels in contact with the ground during the roll. The lateral control of the aircraft is then very much dependent on adequate tyre contact with the surface, so if the surface is slippery a crosswind take-off may not be advisable. As the aircraft accelerates, the relative wind velocity (combining the ambient wind velocity, the aircraft's own forward speed and the slipstream velocity) over the tailplane surfaces will have an increasing headwind component and a (relatively) decreasing crosswind component. Thus, it is normal to start the ground roll with a large rudder deflection to counter weathercocking, and decrease the deflection as speed builds.

 

It is usually advisable to also raise the into-wind aileron to prevent the into-wind wing from rising, particularly if gust-induced; the inclined lift vector, because of the rising wing, will tend to turn the aircraft away from the wind. Be aware that if the into-wind aileron is raised while you are countering the weathercocking with rudder, then you must be operating cross-controlled, which will cause the aircraft to sideslip into wind if you should get airborne in that condition.

 

The aileron deflection is decreased as speed builds, but in strong crosswinds it may be advisable to lower the into-wind wing so that the aircraft is rolling just on the into-wind main wheel. The lift vector is then inclined from the vertical and has a lateral component that counteracts the effect of the crosswind; the aircraft line of roll is kept straight by the friction of that into-wind wheel. If the angle is correctly judged, there should be no stress on the wheel. As the aircraft is being lifted off, return the ailerons to neutral and level the wings.

 

To provide an additional safety margin, hold the aircraft on the ground for a higher-than-normal lift-off speed. If conditions are gusty, add 50% of the wind gust speed in excess of the mean wind speed; e.g. if wind speed is 10 knots gusting to 20 knots, add 5 knots to the lift-off airspeed. If the aircraft does become prematurely airborne for any reason then, rather than let the wheels bump down again, hold the aircraft off the ground, accelerate in ground effect and use the soft field take-off technique.

 

After becoming airborne, the aircraft will drift away from the heading, so to mark a tidy and controlled departure, gently turn the aircraft onto a new heading to compensate for the drift and the 'track made good' will follow the extended line of the ground roll — at least until the aircraft reaches 500 feet agl, at which height regulations allow a turn in the circuit direction.

 

It can be that the crosswind either amplifies or reduces the slipstream and other effects. It may be wise to consider taking off in a direction that takes advantage of that counter-effect even if it means taking off with a tailwind component. Also, there is no rule that says you must always take-off aligned with the centre of the runway or strip; if crosswind conditions warrant it, plan your ground roll at an angle across the strip — edge to edge.

 

 

[djpacro]

In a Husky departing Laramie (elevation 7300 ft) one morning. It was tied down and parked into wind so we got in and I started up. Got some-one to untie it once we were ready to go and I took off on the parking area. An hour and a half later my passenger wanted to get out and the wind was in line with the 6,000 ft long runway at Rawlins. I landed and stayed on the runway pointing into wind with the engine running while my passenger stretched his legs etc then took off into wind.

 

Incidentally, there is an interesting stretch of Interstate 80 around there with regular sights of trucks blown over beside the road.

 

Drivers of vehicles that fail to heed this type of closure will be considered in violation of Wyoming Statute 24-1-109 and 'shall be subject to a fine of not more than seven hundred fifty dollars ($750.00) or to imprisonment for a period not to exceed thirty (30) days, or to both such fine and imprisonment.'Research shows that when wind gusts exceed 65 mph, there is almost certainty that multiple vehicles will be blown over or be involved in a loss of control type of crash

It seems they now monitor the winds and close the highway to some vehicles.You always get a choice as to whether you have a crosswind for take-off or not.

 

I look forward to the continuation of JB's tutorial on landings.

 

 

[motzartmerv]

Thanx Ian. Very useful. I dont know about taking off across the runway being a great idea. Still, great stuff..:)

 

 

[Deskpilot]

This doesn't apply to take off but in the case off landing with a very strong X or quartering wind, use every inch off available space. I was flying with an instructor one day and having a bit of trouble so he took over and showed me a safe way down.....if you have the space. Murray Bridge has 2 runways in the form of an L. Landing up the main leg with a 45 degree wind from top left down to bottom right. Our route was to fly directly into the wind across the bottom of the L.ie, land on the foot, cross the grass to join the main leg and then turn and run along main with the stick hard over to port. All safe. Mind you, watch out for any obstructions like standing lights and cones. Just because the runway is there, you don't have to use it in an emergency.

 

 

[kaz3g]

This doesn't apply to take off but in the case off landing with a very strong X or quartering wind, use every inch off available space.

Good advice, especially in a TW aircraft. I landed at Mildura in a 30 knot nor-westerly and used 36 by coming down on the far edge of the eastern grass and pointing NW. I zig zagged through the PAL lighting on the bitumen and onto the grass on the western side. All good!

 

Taxiing east to the fuel bowser was a real challenge because the starboard wing wanted to lift and she wanted to weathercock all at once. The fuel man just shook his head...

 

Kaz

 

 

[poteroo]

Good advice, especially in a TW aircraft. I landed at Mildura in a 30 knot nor-westerly and used 36 by coming down on the far edge of the eastern grass and pointing NW. I zig zagged through the PAL lighting on the bitumen and onto the grass on the western side. All good!Taxiing east to the fuel bowser was a real challenge because the starboard wing wanted to lift and she wanted to weathercock all at once. The fuel man just shook his head...

 

Kaz

Good thinking everyone. There is no law, to my knowledge, which says you must land on the centreline of a runway or strip. You do whatever it takes to save your hide.

 

An important point here - as you adopt an angle across the runway more into wind, you not only decrease the crosswind component - but you increase your HWC - meaning a much shorter ground roll. If the x/w is 90 deg for t/o - often better to take it from the right as you cancel out some of the full power induced LH swing. Found this very impt in heavier t/w types.

 

happy days,

 

 

[motzartmerv]

Why do you think they paint a centerline on the runway? If we find ourselvs taking off in a wind that is so strong we need to do silly things like that, then we are asking for trouble. Directional control is the issue. Angling across a runway is not going to change the angle very much. I'm not gunna do the maths, but say you have a 1000 meter strip and it's 50 Meters wide, the angle you are creating would not be significant enough (IMHO) to change the crosswind compOnent very much . What it will do is reduce your safety margin by having less room to handle it should directional control become difficult. Runways to be certified must fit certain cryieria with regards to splay areas and runoff ( lateral) areas. By extention one could argue that you are expected to stay inside this area, with room to spare on each side. If you are in a xwind that requires you to adopt this technique I'd want to know why!!!! The crosswind component is either one of two things. 1. Below th rated wind component for the aircraft. Or 2. It's above it . If it's above it, then go fishing. If it's below it , happy days. We are talking about taking off here, which is always optional.;)

 

My 2 cents.

 

 

[Guest Howard Hughes]

There is no law, to my knowledge, which says you must land on the centreline of a runway or strip. You do whatever it takes to save your hide.

Do we need to make a law for everything? Surely common sense dictates that you land in the middle of the runway to allow a safe buffer on both sides of the aircraft? Common sense would also dictate that if the crosswind exceeds the limit for our aircraft we don't go flying (as Motz said)!

Cribbing closer to one side will only put you at more peril if you end up losing control of your aircraft! Or Zig Zagging, or Boot legging!

 

 

[Guest nunans]

Some small slow planes don't need much distance to land in still air so when there's a strong cross wind blowing and you're trying to land where there's no cross strip then I'd rather have a go at landing straight into a 20 knot head wind that's at 90deg to the strip than risk bending my plane trying to land with a 20 knot cross wind component.

 

 

[motzartmerv]

Or you could divert ;) I'd have ago at that first before I risked landing across a runway.

 

 

[David Isaac]

Clearly some with these comments have never flown a heavy tail wheel aircraft within and at the crosswind capability limits ...

 

If they had they would know that in certain conditions particularly in strong quartering cross winds from the left you have virtually no rudder effect until the takeoff speed has increased enough to raise the tail ... and while you are waiting for the speed to increase, the aircraft is merrily moving to the left; stabbing the right brake just prevents the aircraft from accelerating. You just have to hold your nerve until you have directional control.

 

And just to enlighten the theorists, under those conditions you may use the whole available width of the runway until you gain enough speed to gain enough rudder effect and at that time you may find yourself off the bitumen all together and taking off down the grass strip before you can turn the aircraft straight down the runway. It has happened to me in C185s and C 180s (heavy with parachutists) and DC3 pilots have described to me the same scenario.

 

What do you think Potts is talking about above ... and you would have to be bloody brave or stupid to argue with him on this one.

 

I am sure Nev could chime in on this discussion as well regarding large tail wheel aircraft in crosswinds ... they are a whole different ball game aren't they Kaz.

 

 

[motzartmerv]

Yea David your probably right. There's probably a few things that would be different about flying a dc3. Even 185's and the like may be a bit different. But what's this talk of rear and quartering xwinds.?Maybe some sort of operational requirement would force a pilot to perform the described takeoff above. If you or anyone else can describe mathmatically how crossing the strip makes a significant difference which overrides the safety of having ample room on each side if the aircraft, I'll happily consider it.

 

But more importantly, how this technique relates to light aircraft that are flown for fun.

 

All this talk of zigzagging through pal, landing across runways, rear quaterin winds, in light aircraft flown for fun is mind boggling.

 

 

[motzartmerv]

And as you said, they are a different ballgame. The normal ball game is NOT to do it. ;)

 

Cheers

 

 

[naremman]

The preceeding two posts come from two very experienced and respected instructors. Their posts give credence to that old adage: " there are no wrong actions, but certain different actions."

 

As a comparative aviation layperson, one thing that I have observed in nearly 40 years of flying are that not all aircraft are not the same, and not all pilots are not created equal.

 

With aircraft that I have experienced, should I turn up on any given day with a steady 15 Knot crosswind across the only available strip, I would leave the Tiger Moth in the hangar to fly another day, The Cessna 172 I would fly knowing that was the max crosswind allowable for the aircraft and would require a very good piloting standard of me for safe operation, and with the Airtourer I would say "what crosswind".

 

I am sure we have flown with, or observed some pilots where their limits for comfortable and safe operations with crosswinds are inside the limits of the aircraft that they fly. A pilot who recognises their own limitations is probably a safer option than who does not.

 

I have the utmost respect for instructors who are entrusted with equiping their students to steadily acquire the piloting skills, so that when they are deemed competent to be let loose on their own, will do so safely for themselves and those who fly with them. Once they leave the training environment the intstructor has no control of what aircraft they choose to pilot, or where they operate. I imagine they hope (or even pray) that no matter what they attempt they do not exceed their piloting skills!

 

Crosswind operations are the one aspect of aviating where any skill deficiency will become readily apparent. The proximity of the ground only amplifies any shortfall.

 

 

[Guest nunans]

how this technique relates to light aircraft that are flown for fun.

Maybe it would be fun to try something other than "sticking to the centre line just because someone painted it there"

 

For Mr Huges, "Common sense would also dictate that if the crosswind exceeds the limit for our aircraft we don't go flying" I didn't know our aircraft had crosswind limits, I've only seen demonstrated crosswind component information which is just what a test pilot thought was a good thing and may or may not be suitable as the correct limit for all other pilots who fly the aircaft.

 

In the first post there was mention of considering a runway direction that takes advantage of aircraft effects (i thought of gyroscopic effect for a TW aircraft) and I can see the reasoning there, i don't know what all the fuss is about.

 

The last bit "plan your ground roll at an angle across the strip — edge to edge" I'm sure what is intended here is that you are effectively shortening the available runway (which there's a good chance you may not need if there's a stong wind blowing and you're flying a small slow aircraft) as a trade off for taking the wind more on the nose rather than on the wing tip.

 

Merv I agree there would be nothing measurable to be gained by sitting on one corner of a 1000m strip and aiming for the other corner. Instead the intent would be to sit on one corner and aim off the side of the strip part way down.

 

Kaz it sounds like the real limit for you was taxiing with the cross wind not landing with it ;)

 

 

[motzartmerv]

Nunans. I would suggest you reconsider your statement regarding xwind limitations and demonstrated wind etc. I appreciate your opinion and input but there is a bit of a dangerous knowledge shortfall evident in more than one of your above comments.

 

Cheers.

 

 

[robinsm]

The manufacturers of my aircraft have definitely stated a cross wind maximum for it. Over 15kts it aint happening. Common sense applies in that if you are uncomfortable with a cross wind, don't fly in the damn thing or use another runway. I have noticed some pilots don't like grass runways for some reason and yet they are normally available at most airports as an alternate in crosswind situations. If you need to use a cross strip because of conditions, let the other aircraft know then use it. You are better off safe than all pranged up because the sealed runway with the crosswind is what the "crowd" are using.

 

 

[rgmwa]

I didn't know our aircraft had crosswind limits, I've only seen demonstrated crosswind component information which is just what a test pilot thought was a good thing and may or may not be suitable as the correct limit for all other pilots who fly the aircaft.

There are two crosswind limits - the pilot's and the aircraft.

 

rgmwa

 

 

[motzartmerv]

Yes, but one is never higher than the other.;)

 

 

[rgmwa]

Yes, but one is never higher than the other.;)

The trick is to spot the difference!

 

rgmwa

 

 

[naremman]

Nunans, you raise many valid points in your post, but in general place the issue at the extreme end of aircaft operations. Not every pilot is comfortable being that close to the edge.

 

xx Knots demonstrated by a TEST PILOT is an area the average pilot is ever going to approach.

 

The original Handling Notes for the Airtourer that Victa posted, and the original DCA Flight Manual for the Airtourer, stated 20 Knots demonstrated and there are a number of pilots, myself, included (and at night for good measure), who would include safe operations (ie no accident) at excess 20 Knots. The current AFM for the Airtourer clearly states no operations beyond 20 Knots. Should I bingle my Airtourer tomorrow in crosswind conditions the regulator and insurance company will have a singular focus, rather than any any historical perspective.

 

The post by Kaz is notable. The landing/ take off phase may well be not the most hazardous phase of the flight. Taxying in extreme wind conditions may well place us at our most vulnerable. A take off with a 45 degree crosswind exposes the aircraft at less risk than the taxi when the aircraft is at 90 degress to the wind, or in a downwind scenario when the the wind is determined to invert thee.

 

 

[Guest Howard Hughes]

I've only seen demonstrated crosswind component information which is just what a test pilot thought was a good thing and may or may not be suitable as the correct limit for all other pilots who fly the aircaft.

At some point your rudder area and arm is going to run out, do you really want to be the one finding where that occurs? You can't beat physics!

 

I have noticed some pilots don't like grass runways for some reason and yet they are normally available at most airports as an alternate in crosswind situations.

I use the grass when ever I can, after all, there are no bad landings on grass!

 

 

[motzartmerv]

RAA ops manual syllabus reference:

 

Section .3.04-6.Unit 3.1 Takeoff aeroplane.

 

Aeroplane is lined up in the center of the runway in takeoff direction.

 

3.2 Take off power is applied, aeroplane is maintained aligned with the center of the runway with wings level....

 

Section 3.04-6. Unit 5.1 Land aeroplane

 

Aeroplane is landed at a controlled rate of descent, aligned with and above the runway centerline,

 

The above are two references found in the RaAus ops manual syllabus for issue of pilot certificate.

 

If you were to perform a cross runway takeoff or landing during your fight test you would not be complaint with the above syllabus requirement and therefor fail your test.

 

 

[frank marriott]

I find interesting that the J230 pilot handbook does not have a max demonstrated Xwind as with all other aircraft I have flown [GA]. I find the 14kts stated is a good number to use a a MAX but it could be argued that the handbook number is advisary ???????????

 

I guess I am being a bit picky as unless the actual Xwing is recorded at you time of landing as in CTA then it is fairly hard to establish within a few kts what the wind was at your actual landing time.

 

As with most aviation matters commensence should prevail in any case.

 

"3.3 CROSSWIND The maximum allowable crosswind velocity is dependant on pilot capability as well as aircraft limitations. With average pilot technique, direct crosswinds of 14 knots can be handled with safety."

 

FrankM

 

 

[motzartmerv]

Yes frank. We lobbied jabiru quite strongly a few years ago to get them to change the wording in their flight manuals. We were often grounded at Camden due to the atis quoting max xwind above 14 kts. The current wording is a little vague but is better than it was. Our school had a max of 18 kts for the 160 and 230 in the SOP afte jab changed the wording. We had a pretty good idea where the real limit was, which was a few kts more than 18kts.