How do you land a plane in a crosswind?

Factual Questions
1

I saw on the news the other night that Airbus was testing it’s new A380 plane, and part of the certification process involves testing the plane’s ability to land in a crosswind of a certain velocity. Seems like no big deal, I thought…then I thought further.

To compensate for a crosswind, the pilot could “tilt the plane into the wind” by dropping the wing on the side that the wind is coming from (which raises the wing on the other side) and pulling back on the stick, thus compensating for the crosswind. Problem: although the plane is flying straight down the runway, the plane is not level; therefore, the plane will have difficulty landing since the right and left wheels of the landing gear will not touch the runway simultaneously. Dangerous, no? :eek:

Okay, so the pilot could try something else. He could fly level, but use the rudder to “point the plane into the wind” slightly. Straight, level flight…but once again, there’s a problem: the plane is now yawing, or flying slightly sideways. So, the actual landing is once again a problem since touching down will likely result in a loss of control since the wheels (although touching the ground simultaneously) won’t point in the direction the plane is actually moving. Dangerous again, right? :eek:

Okay, so whaddya do? :confused: Pilots?

2

Perpetual flight student here.

You have most of it. Turning the nose into the wind is called crabbing (because it looks like you are going sideways from the ground). It is fairly easy to do and it works well.

There are other methods like dipping a wing to compensate or doing a maneuver called a slip where you use both rudder and aileron in an uncoordinated fashion to do some fancy things like drop altitude quickly in a given direction.

You seem to have the problem illustrated. It isn’t good to land a plane on a runway moving in one direction but pointed in another. The key is that the pilot has to straighten the airplane out very quickly before touch-down. If you do it too soon, the airplane can drift away from the center line and maybe even of the runway. Do it to late and that poor landing gear is going to be hurtin’. Most airplane gear can take some degree of side-loads but they can fail under extreme conditions and the nose gear is the most fragile.

With the banking methods, the pilot has to quickly level the wings and probably make some quick rudder inputs as well. This method has disadvantages because it puts a wing closer to the pavement and if something goes wrong, a wing strike is much more likely. That can be dangerous and very costly.

All airplanes have a maximum crosswind rating. They have a test pilot make crosswind landings until he hits a point where he can’t do them safely anymore. Pilots have to know the crosswind rating for there plane plus wind information before they make a safe landing.

3

Don’t think of this as an answer, because IANAP. Just seeing if my guess is correct when the IAAP people turn up in this thread.

You approach the runway using the rudder to provide the right ‘trim’ against the crosswind. You might even land slightly to one side of centre on the runway. Then you get through the transitional phase the hell fast and use the wheels for control.

Or you divert to another airport.

4

The short answer is, “Poorly.”

It’s hard to describe because it takes place in a three-dimensional world. But I’m sure Sam Stone will be along to try soon.

Meanwhile, I’ll mime it. (imaginary rudder and yoke gestures accompanied by hunched shoulders and squinched up face). It feels like this… Ka-LOMP! And you’re on the ground.

5

(“Cheated death again!”)

6

Shagnasty gave you the basics. One method is to crab the airplane into the wind to compensate for the crosswind. When you’re about to touch down, you either kick the rudder and straighten out just before touchdown, or you let the airplane hit the ground slightly crabbed, and if it’s a nosewheel airplane the forces involved will pull the airplane into line. This can be hard on landing gear and tires, in the case of a small airplane like a Cessna, or break things in larger planes. Kicking the airplane straight requires a little touch, because if you do it too early, the airplane will begin drifting with the wind again before the wheels touch, and you’ll put a side load on the landing gear.

Boeing found a third way with the B-52: they allow the landing gear to be rotatedslightly in flight, so the B-52 can land crabbed, but with the gear facing straight. It has to do this because the fully loaded bomber’s wings are so heavy and long that sideslipping is out of the question. So the pilot dials in the crab angle, and the gear rotates in the opposite direction.

Sideslipping by tipping a wing and applying opposite rudder puts the airplane in line with the runway, and as long as wing clearance allows it, you can touch down in that configuration. It requires a fair touch to do it well, though. And in most airplanes, rudder authority limits the amount of crosswind you can handle. If it gets too high, you just can’t apply enough rudder to keep the airplane straight.

Tailwheel airplanes are tricky in a crosswind, because if you put a side load on the tires or land crabbed, the tail will want to swap ends because the center of force is ahead of the center of gravity, which is unstable. Off-axis loads tend to start the back end pivoting. In a nosewheel aircraft, side loads tend to pull the nose back into line, which is stable.

Personally, I try to fly the airplane crabbed onto short final, then rotate it back to the centerline while dropping the wing a bit to keep it from drifting, and trying to time the whole transition so that the airplane arrives on the runway pointing straight ahead and with the wings almost level.

The operative word is ‘try’. Crosswinds are always tricky. Our old Grumman AA1 handled crosswinds like a dream. I could grease that airplane onto the runway in just about any wind. I even flew in a spot-landing contest and had to try to hit a spot on the runway with a 15-20 kt crosswind.

But I always embarass myself in Cessnas. They just tend to buffet around so much and float when landing flaps up as you do in a crosswind. The combination is that I usually flop onto the runway like a fish landing in a boat. It gives me a chance to say, “Well, any landing you can walk away from is a good one, huh? Am I right?” which is always fun.

7

Good replies by Shagnasty and SS.

Not especially, provided the upwind wing (or what’s hanging off it, such as engines) doesn’t get too close to the ground.

Potentially. As others have noted, a common approach is to time the input of downwind rudder so the plane is facing the direction it’s moving just as it touches down.

Though I don’t know the details, I’d assume that one thing they must include in their test is a demonstration that the A380 can safely handle a specified amount of “sidewaysness” in a landing, and probably at a very heavy weight.

8

Here’s a video - just amazing that such a huge machine can be manipulated like a dirt bike!

9

Here’s a short video of a 747 landing at Hong Kong’s old Kai Tak airport, showing some of what’s been mentioned. This place was legendary for its tricky pattern and conditions; this pilot just barely managed to pull it off.

10

And if you really know your bird and it is a twin, you can use differential power too.

You can land diagonally on the runway if you are small and the runway is big. In some cases, I just land cross ways on the runway. Take off that way also.

I always felt that of the planes I flew regularly, the Piper Cherokee Six had the most wimpy rudder. The straight tailed Cessna’s had some of the best rudder control. YMMV

Circling approaches will sometimes work with small planes also in strong STEADY cross winds.

What seems to get a lot of pilots in trouble is they don’t check farther out on final to see if they have enough control to do the landing. They wait until they are low, slow and then if they don’t have enough control, they are already bankrupt and things end badly.

Right at ground level, it may be significantly different from a ½ mile out and several hundred feet up but if you don’t have the experience and knowledge to handle it and make those judgments safely you should not have been up that day in that place in the first place. YMMV

In heavier tailwheeled airplanes, the big mistake seems to be the idea that if the plane is starting to go wonky, they put in some rudder and wait to see if that is enough, ( usually is not ) when they should be putting full deflection in and then releasing it if it is too much. You can’t let a short wheel base aircraft, like a Swift get started swapping ends or a heavy one like a Beach 18, they will eat your lunch.

Broomstick talks about “Move your feet” and that is the most important part of controlling aircraft in crosswinds along with good preplanning.

11

If you look at the last couple of landing in the video that K364 linked to you will see that a 777 can also crab the mains. Look at the camber angles on the mains on the approach.

12

And here’s an A380 Airbus crosswind – perhaps the very test referred to in the OP.

Interesting how both landings appear to take place at the same airport. Makes you wonder if they built the airport solely to do crosswind tests – or if they built the airport first, realized too late that severe winds rendered it useless to big birds, and then some Boeing test pilot said, “Hey! This gives me an idea…”

13

I got e mailed a copy of K364’s video, and the note with it said that these videos were taken at an Air Force base in Brazil. There was some text on the screen that could well have been Portuguese. I suspect that if this is the case, this base is in a place where the wind comes from one of two directions about 90 degrees apart. i would also venture to say that there is a 2nd runway that is head into the wind.

14

I think the pilot in this video should read this thread. He very nearly makes a complete hash of the landing.

15

mittu that link doesn’t seem to be working.

Everyone else has pretty much covered the two techniques. Personally I far prefer landing one wing low. You just keep the nose aligned with the runway with rudder and apply enough bank to keep from drifting. The big advantage is that the aircraft is always under direct control (whereas the other technique relies on timing), the disadvantage is that on some aircraft, a wing or whatever’s hanging off it, may touch the ground.

Touching down one wheel at a time isn’t a problem, in fact it can make for nicer landings.

I refer to the technique as “three dogs barking” because that’s the sound you hear as each wheel touches down, yelp…yelp…yelp.

16

Yeah, that’s a pretty famous example of how not to do it. First the dude overshoots finals on his turn so has to fly back to the centreline leaving himself with a very low turn to get lined up. In the end he actually touches down on the downwind wheels first and well to the right of the centreline.

17

Most of the techniques described above for light aircraft aren’t usable by the big guys with engines hanging under their wings - they can’t go wing-low enough to compensate for all crosswind conditions or they’ll drag an engine. Annoying the passengers with a tilt to the side is another factor.

An airline pilot will hold the crab all the way into the flare, then kick the rudder straight while settling down through ground effect so that crosswinds have only a few seconds to work. That’s tricky to time, and it’s common to land with a little side load on the mains anyway, but they’re built to take it (the A380 video shows a test to certify the amount of side load). My regular flying partner, a retired DC-10 captain, insists on doing that even in his light single, partly out of habit and partly because it requires less reaction to gusts than a wing-low landing (which projects more area into the crosswind). I’ve tried it but can’t do it proficiently (yet), because it means doing one more thing at the trickiest point.

Private pilots are trained to crab into the wind to stay level (and to avoid fuel starvation if drawing from the tank on the low wing), then transition into a wing-low slip over the fence, then touch down one wheel at a time (which is NOT dangerous), keeping the ailerons into the wind until slowed to taxi speed. Crosswind takeoffs are the same, ailerons into the wind, nosewheel off first, then the downwind main, then the upwind main, climb wing low untill 500 feet off, then turn onto course.

The Ercoupe has the rudder and ailerons connected so you can’t get into a cross-controlled stall, which means you can’t land wing-low either. You land an Ercoupe in the crab, and count on those beefy mains to take the side load.

The B-47 and B-52 have fore-and-aft mains that can be rotated away from the fuselage axis. Those planes are also landed in a crab, but with the wheels pointing down the runway.

Boeing does most of their testing at Moses Lake, Washington. Don’t know about Airbus.

18

And the rest of ya’ll talked so much there nothing left for me to contribute in this thread!

S’alright. I’ll mention that knowing both the machine’s limitations and your limitations are important, and in real life a smart pilot flying on a windy/gusty day will keep in mind an airport with runways lined up with the wind just in that crosswind starts to exceed limitations. My Indiana home base airport gets a number of calls every year from pilots who were intending to use the single east-west runway but wound up diverting to Gary because of crosswinds - folks are happy to pick them up and give them a ride home if needed.

I’ve landed a Cessna 150 in a 25 knot crosswind. It wasn’t much fun, I don’t recommend it, and I certainly didn’t intend to get into that situation, but it can be done and done well. If I had to, I could do the same in a C172 or Piper Warrior. I also know that I could not do that safely with, say, a Citabria or an Ikarus, in those airplanes I’d have no choice but to divert. Half the battle with staying safe is knowing stuff like that in advance so you can make decisions that keep you out of trouble in the first place.

A co-worker once asked me at what point in the flight do I start worrying about the landing. I said I start thinking about the landing no later than a half an hour before take-off. When Gus and the other pilots are talking about “preplanning” that’s what they mean. It starts a lot earlier than non-pilots are usually aware of.

19

On preview I see Elvisl1ves & Broomstick have already contributed much of what I’ve said while I was typing, but having invested the effort I’ll go ahead & submit …

Former Boeing driver here …

You guys have it all pretty much figured out, so there’s not much for me to add.

For large aircraft, the slip method doesn’t work well due to the long wings & in many cases underslung engines. So the typical approved procedure is to crab until the flare & remove the crab with rudder just prior to touchdown, with a just dab of upwind wing-low to minimize sideways drift as the crab comes out.

Add the fact that the wind usually shifts significantly from 300 feet to the surface, and strong winds almost always imply turbulence, and the workload for a high-wind landing can easily be 10x that of a no-wind landing.

Despite what somebody said above, big jet landing gear is quite tolerant of touchdowns in a crab; it has to be. Naturally, there is a limit for everything & that guy in the Airbus would have been close had he touched down. My PC (or at least my ad & flash blocking) hates youtube so I can’t review the videos linked above.

As others have noted, some aircraft have partly castoring main gear that can pivot to align with the path down the runway even if the fuselage is not so aligned. The 737 gear can do that a bit. The B-52 was unique in that the castor was controlled from the cockpit before landing rather than just being a mechanical result of impact forces at touchdown.
Minor item from waay up the thread … Somebody describes crabbing as using rudder to fly “sideways”. Wrong. A crab is fully coordinated straight flight through the air. The rudder is centered & the airplane is NOT flying sideways.

What IS happening is the airplane is flying straight through the air, while the air is moving sideways over the ground. From the POV of a ground observer, it appears the plane is sliding sideways. It IS sliding sideways through the sky but not through the air, if you get the distinction.

From the POV of the cockpit, we’re flying straight through the air while the ground is sliding sideways under us.
Fun factiod: Typically jets don’t have a formal maximum crosswind limitation. What they have instead is a “maximum demonstrated crosswind component”. The typical value is 29 knots. In other words, the factory flies the thing to a landing where the wind vector 90 degrees to the runway is 29 knots. And they live to tell the tale. They don’t say you can’t successfully land at higher crosswinds, merely that you are acting as a test pilot if you do. All carriers I’m familiar with treat the demonstrated value as a hard limit, barring emergencies (or landing in Hong Kong.)
I recall one memorable afternoon just following a cold frontal passage. It was clear, cold & winds on the ground were about 45 degres off runway axis at 20 knots gusting to 30, or so they said. At 2000 feet above the ground where I was our computers told us the winds were about 90 degrees off the runway at 120 knots. We’re only doing about 190 knots at that point so I’m watching the runway not out the windshield, but out my side window.

We knew all that change in wind direction & speed had to happen someplace between here & the ground, some 2+ minutes away. “This should be fun …” we thought. Turned out to our pleasant surprise that the wind just smoothly slowed & changed direction down to about 100 feet, then the turbulence picked up a bunch & I set down with no fuss at all.

Our textbook expectation was a large wind shear with an abrupt dropoff at some point, but it just wasn’t there. Another object lesson that you don’t do aviation, you “practice” it, like medicine. Micro-weather is just not textbook.

20

The airport I fly out of only has one runway, so 75% of my landings have been crosswind.
Rudder authority does limit crosswind landing, but it is possible to stretch the limits by carrying more power (makes the rudder more effecive).
I’ve taken the rudder to the limit a few times - not fun, but certainly doable.

For what its worth, I learned the bank into the wind, use the rudder to line up with the runway all the way after turning to final.

Brian
“slips with flaps”