We all know that the maximum demonstrated crosswind value listed in airplane manuals is not a limitation. The crosswind speed listed is the strongest crosswind component test pilots successfully handled during developmental flying. Some pilot operating handbooks show demonstrated crosswind in the first section along with limiting airspeeds but Beech lists it in the “normal procedures” section along with other “airspeeds for safe operation.”
The maximum demonstrated crosswind for my airplane is 22 knots. I don’t know if I have encountered a crosswind component that strong, but in 5,000 hours of flying the same airplane I think I have come close. And 22 knots is a lot to stop sliding sideways.
Of course a crosswind is seldom 90 degrees to the runway heading. What we’re concerned about is the component of the wind that equals a 90 degree crosswind. So if the wind is blowing 30 knots I get concerned when its direction is more than 40 degrees left or right of the runway heading.
In the perfect world of airplane manuals and test flying the wind is steady. In our real world of flying the wind is often varying many degrees in direction and gusting many knots. If the wind were a steady 10 knots directly across the runway that would be pretty easy to handle. But if the wind is blowing 10 knots with gusts to 25 even though the direction is only 40 degrees left or right of centerline, that’s a different situation.
The crosswind capability of an airplane actually has two elements. One issue is flight control authority, and the other is capability to stay on the runway during rollout.
Identifying the crosswind limit in flight is really pretty easy. If you have the rudder or ailerons–or both–at the control stops and the airplane is still drifting sideways you have found the crosswind limit for what most of us consider to be an acceptable landing.
An airplane’s capability to handle a crosswind after touchdown is much more complicated. Among the many factors involved are the deck angle of the airplane on its landing gear, the traction available from the tires, the geometry of the landing gear wheelbase and track, and availability of lift killing devices.
It only takes a second to realize a taildragger lacks nearly all of the capabilities to defeat a crosswind during rollout. A taildragger is going to reach its crosswind limit at that critical point where the rudder is losing effectiveness, the tailwheel is not producing any traction, the downwind brake and tire are losing grip, and the wing’s angle of attack is increasing as the tail comes down.
The situation is the opposite with a tricycle landing gear. As the airplane slows more weight shifts from the wing to the wheels providing increased tire traction. The nose wheel gains more authority as weight shifts forward providing positive directional control. And the geometry of a trike landing gear causes the nose to swing away from the wind and straighten after touchdown, exactly opposite of a taildragger.
But in either type of airplane it is the crosswind gusts that can ruin your day. If a powerful gust strikes during the critical phase of touchdown and rollout you may find the crosswind capability of your airplane has been exceeded in an instant.
What can you do to increase your chances of not finding the true crosswind limit on a gusty day? In airplanes that lack effective ground spoilers–and that’s the case for most of us–I think the best approach is to not use full flaps. With only approach flaps, or no flaps down, the airplane has reduced ground effect and transfers the weight to the wheels more quickly. Most airplanes also float less without full flaps extended, and floating along with a gusty crosswind is a good way to wind up in the weeds.
The difference in stalling airspeed between flaps up and flaps down at a typical landing weight in my airplane is about 9 to 10 knots. The book doesn’t show stall speeds with only approach flaps extended so I add the full value difference between full flaps and no flaps stalling speed to approach speed when landing with only approach flaps. The increased airspeed on approach will require some added runway length, but if it’s windy enough to be concerned about landing and stopping the wind is lowering groundspeed and required runway anyway.
Somewhere along the way it became FAA dogma that was passed down by instructors that you should always use full flaps when landing. In large heavy airplanes, that makes sense. But for piston singles and twins it doesn’t always. On that gusty day I find there is more control available without full flaps. I can hit the touchdown target more predictably, and control on rollout is enhanced without the full flaps.
Be sure you have plenty of runway margin on a windy day and give the partial flap approach a try. Your airplane will still have a very real crosswind limit, but I bet you will find you have more control without the full flaps.