Crabby Pilots?

Question:  Some flying articles have referred to a flying technique called crabbing. What is crabbing? How and why is it done? How are pilots trained to successfully accomplish the technique?

Ray G., Rochester, New York

Answer:  Crabbing has to do with landings when there is a cross-wind.  Say you're headed toward the runway in a zero-wind condition.  The airplanes' nose (as well as your own nose, too, I might add) is lined up with the runway.  Same goes if there is a wind that is straight down the runway.

However, imagine you're pointed right at your runway with a crosswind of, say 30 degrees off your nose from the left at 15 knots.  It should be obvious that the wind is going to push you over and when it does, you'll still be pointed the same direction as the runway but you'll drift and no longer be lined up with it.

So the pilot "crabs" into the wind, named so after the sideways gait of actual crabs.  Now we point the plane just a few degrees into the wind and have to turn our head just slightly to the right to see the runway, but we can see our course is now lined up once again.  We can look out the window to see this in visual conditions or use instruments, such as an Instrument Landing System (ILS) localizer, which is the part that keeps us on course (whereas the Glide Slope keeps us on our vertical path).  Our heading refers to where our nose is pointed, while our course is our track over the ground.

If we're on autopilot, the autopilot will "capture" the localizer (lock onto it) if there is one and keep us on course straight toward the runway with the plane's nose pointed somewhat to the left in our example, or the pilot can manually correct the heading a few degrees at a time while on autopilot, or steer the plane him or herself.

When actually landing, in order to avoid landing sideways and putting a side load and unnecessary stress on the tires, we straighten out the nose until we're lined up once again with the left wing just a little bit lower (into the wind), and add a little right rudder to keep the airplane headed straight down the runway for landing.  If you've ever felt your plane land on either the left or right wheel first, chances are good the pilot was landing with a crosswind.

This cross-control maneuver is called a "slip" and in small airplanes, a pilot might slip the plane to lose altitude more quickly or keep the plane lined up with the runway rather than crabbing.  In large planes, however, we don't use the slip maneuver--rather we crab down final and put the plane into a slip sometime before the flare or even in the flare, depending on the pilot and the airplane. The flare is that part of the landing where the pilot "checks" (slows down) the rate of descent by raising the nose just prior to touchdown.

Crosswind landings are something every pilot learns while obtaining his or her Private license.  It's a maneuver at which every pilot must become proficient early on as it's such a part of everyday flying.