Get Crabby and Know When To Slip Away
Hey Mom,
I’ve just started working on landings and my book says that there are two different techniques for landing in a crosswind. One is to slip and the other is to crab. It says I can use either one. How do I know which is better? I think I get the crabbing, but I’m pretty sure I don’t understand how slipping works.
Thanks for explaining,
Crabby and Slipping
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Dear Crabby (one of the few times this phrase can be uttered with impunity, I’m certain),
Great question. The answer is that you’ll need to be able to perform both and to know when one is called for versus the other. If you’re starting work on landings, you’ve probably already been exposed to ground reference maneuvers. The rectangular course is all about preparing you to fly traffic patterns (ah ha! There is indeed a method to the madness!) As you’ll recall, the idea is to turn the airplane into the wind enough that you are able to fly a straight ground track even with a crosswind. Crabbing involves coordinated flight, i.e. wings level and ball centered. The angle you’ve chosen to point the airplane into the wind is what keeps you from being blown off course. Crabbing is useful to us through most phases of flight. It’s how we compensate for crosswind component during cruise flight as well as on each leg of the traffic pattern. The only place where this very convenient and coordinated condition becomes a problem is when we start thinking about touching down. The landing gear on your airplane doesn’t swivel (not usually. If it does, we’d better have a chat with your mechanic, pronto!). If you touch down in a crab, you put a side load on that landing gear. It’s tough on the airplane and none too comfortable for you, either. In a strong enough crosswind, it can be downright dangerous. Hence the need for the slip.
A slip is an uncoordinated maneuver, meaning that it’s about the only time we’re going to encourage you to go one way with the ailerons and the other way with the rudder pedals. Normally, you pull something like that and your flight instructor is going to start getting excitable. There is a very good reason for this. As you’re probably well aware, an uncoordinated stall is begging for a spin. Consider that a slip is a maneuver most often performed in close proximity to the ground and you can imagine the potential for disaster. Should the airplane stall (most unintentional stalls occur on the base to final turn, at a very low altitude indeed), you may not have the necessary altitude to recover. So DO. NOT. STALL. while performing a slip. Also consider that in a slip, you have turned the static port either into or away from the relative wind and the pitot tube out of it as well. Your airspeed indicator will not be as accurate as you’d like it to be. How far off is it? Good question. Let’s not find out. Add a safety margin of at least 5 knots to your final approach speed. Your friendly flight instructor will be happy to tell you what will work best in your airplane.
Scared yet? You shouldn’t be. A properly performed slip is a safe and very useful maneuver. Also kinda fun. Airplanes without flaps perform them as a matter of routine to help lose altitude for landing. So how is it done? On final, with the airplane lined up with the centerline, use the ailerons to control for wind drift. Ailerons into the wind. You’re using them to steer, to correct for lateral drift, to keep the airplane from being pushed downwind and off the runway. Use the rudder pedals to straighten the nose. Step the direction you want the nose to go, which not coincidentally, will be the opposite direction from the ailerons. You have to intentionally separate the use of the ailerons and rudder pedals to accomplish this correctly. It takes practice. For most pilots in most airplanes, a crab will be maintained on final and changed to a slip before touch down. For the student pilot, the transition to the slip should happen early enough to allow time for adjustment, And readjustment. It should be remembered that the wind will usually change at least a bit, in velocity and often direction, with altitude, so expect to keep varying that slip all the way down, all the way through the flare, and all the way until the airplane has entirely finished flying.
Be patient with your own learning process on this one. Most students, heck, most pilots, find the crosswind landing to be one of the most challenging maneuvers to perform. If it’s been a while since you’ve had much crosswind landing practice, don’t be shy about rounding up an instructor to help you put the final shine back on your potentially rusty skills. It’s cheap insurance. And all of you, don’t forget to calculate crosswind component before you take off so that you have a good idea what you’re getting yourself into. The headwind/crosswind component chart can be found here.
Consider that instead of flying in a coordinated way, you’re essentially turning the broad side of the airplane into the wind. Your rate of descent will increase. You can use this to your advantage to help yourself scrub off excess altitude if you find yourself higher than you’d like to be, even if there is no cross wind. This gem of a maneuver is known as a forward slip. Know your airplane as some will have limitations on slips with certain flap settings.
Be crabby and slip away,
Mom
