Thousands of book and magazine pages have been devoted to crosswind landings. There's a good reason for that. Few aviation subjects are dearer to a new pilot's heart or raise apprehension levels more than crosswind landings.
Crosswind landings are typically taught in one of two basic ways, sideslip or crab-and-kick. Both techniques have their devotees, but just as not everyone is either a Democrat or a Republican, there are those who think there's a better way to explain landing an airplane in a crosswind.
| Photograph by Chris Rose |
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Click the picture above for an enlarged view. A new window will open, so please turn off any pop-up blockers. In the crab-and-kick method, the airplane is turned into the wind on final approach and then straightened just before landing by kicking out the crab angle with rudder. As the left hand illustration shows, expect the airplane to drift downwind in the flare. In the sideslip method (shown on the right), the airplane is flown on final approach and through the landing with the nose pointed straight down the extended runway centerline and the upwind wing lowered to maintain directional control. |
First an argument has to be made that regardless of what technique you use, you'll never get good at it if you don't practice. This is another way of saying, "Don't avoid flying in crosswinds; go looking for them. Embrace them." You should seek them out, with an instructor if necessary, and get to know their many nuances, diverse personalities, and the cute little tricks crosswinds can have up their sleeves. In this case, familiarity doesn't breed contempt--it breeds confidence, skill, understanding, and safety, all of which are necessary if you expect to make aviation a part of your life.
So, why don't some pilots wholly agree with either the sideslip or crab-and-kick method of handling crosswinds? What's right about each of them and what's wrong? And what possible new technique can be proposed? The answer is that it's not a new technique as much as a different, simpler way of looking at an old one.
The crab and kick
In the crab-and-kick method, it's commonly taught that you correct for the crosswind on final by crabbing into the wind, and then kicking the nose straight at the last moment, just before the wheels contact the ground in the flare. So, there you are, coasting down final with the nose into the wind and the wings level, ball centered. This is a perfectly coordinated situation with the only gotcha being that the airplane's nose isn't lined up with your line of travel (ideally, the extended runway centerline). While in this configuration, it's necessary to compensate for changes in wind velocity as you get closer to the ground, which is true in all crosswind-landing techniques.
The wind velocity right on the runway surface, in the last fraction of an inch, is theoretically zero. Then, as you get farther up away from the runway, the velocity increases
until it reaches the level shown by the windsock at maybe 15 feet. As you're coming down final and entering ground effect the ability of a crosswind to push you sideways generally decreases. So in the crab-and-kick method, you must change the angle of the crab so the line you're traveling doesn't change. The change in the crab angle usually isn't significant. If, however, there is a healthy gust spread and the wind has hard gusts that come from a different direction than the main wind, it will gradually push the airplane sideways off the extended runway centerline unless the nose is shifted into the gust as it hits, and then returned to the original crab position as soon as the wind dies down. This has the nose wiggling back and forth. In a strong wind, this can be uncomfortable and unnatural.
Some of the controversy about this method is centered on what happens right before touchdown, as the nose is kicked to track straight down the runway. Prior to that moment, the sideways vector generated by the nose being pointed into the wind counters the sideways push of the wind. It's pretty obvious that the instant the nose begins to be brought around to line up with the centerline, the vector countering the wind is removed and the airplane can't help but begin moving sideways. Even if it's a light five-knot wind, when you begin removing the crab the airplane will start moving sideways. However, in a small wind the aircraft's inertia may be enough to let it hesitate enough just before beginning to move that it might touch down with no drift. The operative word is "might." That would be highly dependent on kicking straight at the very last second. It would also depend on luck.
If, in the above situation, the kick is a little late, the nose will be into the wind on touchdown. If the kick is early and the wing isn't lowered into the wind, the airplane may be lined up longitudinally, but it will be drifting downwind. Either way the potential exists for an imperfect touchdown, in which the gear experiences an unnecessary side load. If the pilot balloons as he kicks straight, and there is a solid wind pushing him sideways, a sizeable drift can set in. Simply put, by only kicking out the crab, it's nearly impossible to touch down without at least some side load.
The sideslip
Using a sideslip to cancel the crosswind is a popular method because it gives more control all the way to touchdown and makes adjusting for the variables easier. There are variations in the execution of the approach--the slip can be entered at different places on final, for example--but everyone does the final portion essentially the same way.
So, you're coming down final and the wind is pushing the airplane sideways. You start the approach just like the crab-and-kick method, with the nose into the wind, wings level, and ball centered, so the airplane tracks right down the centerline. The only point of disagreement on this technique is at what point on final do you roll out of the crab and into the sideslip? One school of thought has you enter the sideslip well out on final, one-half or three-quarters of a mile or more. The wing is lowered in the same direction the nose was pointed (this is the upwind wing; the crab is handy for telling us where the wind is coming from and how strong it is) and opposite rudder is applied to keep the nose pointed straight ahead. The angle of bank may be varied to match the wind, including changes to compensate for the gusts.
A note on applying the sideslip while still well out on final: although this method is perfectly acceptable, it may be overkill in that at the higher altitudes of a long approach you're dealing with a wind that is quite a bit stronger than you're likely to experience as you get into ground effect. Another drawback is that it can become really tiring because you're working a harder wind longer than may be necessary--and it may make your passengers uncomfortable. One benefit of rolling into the slip so early is that it puts your brain in crosswind mode much earlier and you focus on the centerline early. This avoids any possibility of being surprised by the wind, which can happen if you roll into the slip too late.
When you're in the sideslip, gusts from the side can change your ground track, so you instantly change the bank angle to keep moving straight ahead. The amount of change in bank angle is actually fairly small. You'll already be banked at an angle that cancels the basic wind, so the additions and reductions for gusts are small and the angular changes don't shift the nose much. Yes, if there's a huge gust, and a lot more aileron is required, you may see the nose try to change direction--which will require more or less rudder. That, however, seldom happens. Still, assume that the wind holds some surprises.
A more common method of utilizing the sideslip is to wait until the airplane is fairly close to the runway and is ready to enter ground effect, say 30 to 50 feet or so. You're in the crab until that point and you can easily see what kind of wind you're dealing with, so you apply some aileron to hold the upwind wing down and, at the same time, apply as much opposite rudder as needed to pull the nose around and align it with the runway centerline. As you settle into the flare, make sure the amount of bank matches the wind and that the nose remains pointed straight ahead. You'll touch down on the upwind wheel and, unless it is a hellacious wind, will come down on the other main wheel almost immediately. Hold the aileron deflection after rollout and be prepared to add even more aileron into the wind as you slow down, especially in a strong, gusty wind.
A variation on the sideslip
Some pilots intellectualize crosswind landings so much that the thought process becomes the problem, not the wind. When focusing on the concept of cross-controlling into the flare there's entirely too much thinking going on. Instead, there's a way to approach crosswind landings in which you don't think about it, you just do it.
Rather than homing in on the theory of cross controlling, concentrate on what's happening in the windshield. Use this to simplify the whole process by forgetting about the cross-controlled mode (right aileron, left rudder, et cetera). Replace it with an understanding of the three primary goals to be accomplished during landing flare. They are to (1) hold the landing attitude; (2) keep the tail lined up behind the nose (no yaw); and (3) stop the drift caused by the wind.
We'll skip number one for now, as that's a subject for another discussion. Instead, concentrate on rules two and three. First, rule two says not to let the nose move sideways. To prevent that, use the rudder to constantly keep it aligned with the runway centerline. It's the job of the feet to keep it lined up before touchdown and the eyes will be aiding in that job. They'll be focusing on the nose and centerline, making sure they agree with one another.
Rule three says, "Stop the drift caused by the wind." Since the crab is no longer being used for correction to stop the drift, that leaves ailerons. Simply bank into the wind until the drift is neutralized, and don't think about cross-controlling.
Just because some aileron is extended into the wind, it doesn't mean opposite rudder is absolutely going to be needed. If it's just a tiny bit of aileron, which is often the case, it probably won't generate a noticeable turning tendency. If it's a big wind and it takes a lot of aileron to neutralize the drifting, there's going to be a turning tendency that you'll have to counter with opposite rudder, which also controls weathervaning caused by the wind. But, don't think of it that way. In fact, don't think about it at all. Just concentrate on the view over the nose. If the amount of aileron you use is enough to move the nose, what's rule number two? Keep the nose straight with your feet. If the nose doesn't move, don't change the pressure on the rudder pedals. If it moves, use some rudder. Simple as that.
If you're in a giant wind and find that you're using all the rudder and aileron the airplane has to offer--even when purposely aiming diagonally across the runway into the wind to reduce its effect--but the airplane is still moving sideways, you've reached the airplane's limit. That's nature's way of telling you to go around and find another runway, at that airport or another airport, that's better aligned into the wind.
Forget about preplanning the landing, just look over the nose. If it isn't straight, use the rudder pedals to straighten it out. If it's drifting, use aileron to stop it. One of the beauties of this approach is that you're not going to be surprised because you counted on one kind of wind, but got another. Just control whatever happens in the windshield.
This method covers every eventuality in every airplane: Use your feet to straighten the nose, your hands to stop sideways movement. See, it's not that complicated after all.
Budd Davisson is an aviation writer/photographer and magazine editor who has written approximately 2,200 articles and has flown more than 300 different types of aircraft. A CFI since 1967, he teaches about 30 hours a month in his Pitts S-2A Special. Visit his Web site.
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