Autopilots, Crosswinds and Air Masses

If you were using rudder you were using the wing low method whether you realized it or not. In fact you you were using the rudder to maintain the aircraft centerline aligned with the runway and using aileron to maintain lateral alignment...whether you realized it or not

It is absolutely true that an aircraft knows nothing about the wind, and is flying in completely still air. The whole business of "navigation" is concerned with flying to "some other point" so that by the time you have spent the requisite time in the air, the wind (if any) has carried you to the point on the earth to which you actually want to get. The triangle of velocities, etc.....

But as noted above several factors keep confusing the situation...

Obviously the aircraft feels the wind indirectly, as turbulence is created by airflow over the ground below. But that is just a pedantic point; irrelevant to the navigation situation.

There is also a change of wind anytime there is a change of altitude. In the N. hemisphere, as you descend, the wind turns to the left, so if you are flying a descent in the very low levels, say 1000ft to zero, as one would on say a final approach, you are having to continually turn left and more left - with apologies to Heseltine

The yaw situation also changes in a descent. Everybody (even me) notices the ball is not in the middle during a climb, and usually a lot of rudder is needed in a climb, but (in my TB20 anyway) the ball, set up perfectly in cruise, is also off to one side during a descent. I don't know if this is due to the lower power or due to the pitch angle, but if one corrects it manually (with the rudder pedals) it can give the impression there is a "crosswind" felt by the aircraft.

There are various inertia effects e.g. after a takeoff into a crosswind you most definitely do feel the crosswind on one side of the aircraft, but that's because the aircraft has momentum along the runway track. That dissipates after some 10-20 seconds, after which the aircraft has yawed to a heading appropriate to the new velocity triangle, but not before one can get a really impressive rate of climb by throwing that momentum into the wind gradient. I have seen +3000fpm when departing with a reported 30-40kt wind There is a similar inertia effect when landing again because the aircraft has momentum along the current velocity triangle, but the pilot has to twist it round to line up with the runway, and at that point any crosswind is most definitely felt on the side of the aircraft.

The "downwind turn" is a total myth unless there is a big change in altitude which then takes you into a different wind direction, or there is a different wind prevailing in a part of the circuit (unusual, I would think).

Re crabbing / wing down, I thought that airliners do the former for passenger comfort. It is really disconcerting otherwise especially if you have no forward view, and you spill the champagne. The advantage I have heard of the latter is that it gives you an earlier opportunity to detect that the crosswind is outside the rudder authority. I always crab, and use the rudder at the very last moment only. This is assisted by the considerable inertia in yaw during the flare, with the yaw caused by the big change in the velocity triangle in the last few feet above to the ground, which is often strong enough to line the aircraft up with the runway all by itself, so the pedals need to be used only after this effect has dissipated.

... but I needed the rudder to stay on the centerline.

Because the wind usually changes a lot between 200ft and ground level. Both in direction and strength do to friction with with the ground. Therefore you need your controls to adjust for that change, which is a gradual process all the way down.

As AnthonyQ wrote, I avoid crossed-control wings low landings with passengers on board (even if they are much more accurate to fly) because it is unpleasant and scary for them unless the crosswind is really strong.

Peter: Everybody (even me) notices the ball is not in the middle during a climb, and usually a lot of rudder is needed in a climb, but (in my TB20 anyway) the ball, set up perfectly in cruise, is also off to one side during a descent. I don't know if this is due to the lower power or due to the pitch angle ...

That is due to engine torque and asymmetric slipstream and only applies to propeller driven aircraft (SE and ME with the propellers turning the same way) when you change power. In "symmetrically powered" aircraft like most jets and MEPs with counter-rotating propellers (e.g. Piper Seminole) there is absolutely no motion of the slip ball with power changes.

but on a final approach with wings level you DO need constant rudder pressure to stay on the centerline.

Getting to a point laterally is the same, regardless of whether you are navigating to a point cross country, or "navigating" to the touch down point of the runway.

You could, if you were so inclined, use your navigation computer to work out which heading (slightly into wind) you need to fly on final approach, and use that (although on final the wind shifts a bit, so you have to adjust the heading on the way down).

To maintain a heading wings level, you don't need any rudder [assuming you are in trim].

The "wing low" method achieves exactly the same heading, but by sideslipping into the wind. You could also use a side-slip to fly a heading during cross country navigation, but it would be tiring very soon and you would be quite a bit slower...

Alexisvc,

The nose wheel is used for turning while taxiing and is not a good landing wheel. Some aircraft, in particular Piper Cherokees, have direct steering linkage to the nose gear from the rudder pedals. These aircraft, if the nose wheel touches down while the pilot is providing rudder input, will abruptly exit the runway in the same direction. Of the training wheel airplanes (tricycle) Cherokees have one of the worst records of loss of control on landing in a crosswind. The Cessna trainers have springs that pull on the nose gear steering and aren't directly connected to the steering, so will be more likely to straighten out after touching down. I don't know what your converted P210 uses for steering linkage, but it appears that you are touching down in a crab, then losing directional control.

For most high wing aircraft, using a crab on final and transitioning to a wing low on short final, using the ailerons to counter drift and the rudder to keep the centerline of the aircraft aligned with the runway gives the best results. Don't stop using the ailerons on the roll out, you should end up with full aileron into the wind as you slow.

A variation of the crab method is to kick out the crab just before touchdown, but this requires great timing and it is easy to set down in a crab. Even setting down wings level in a crab, but keeping the nose wheel from contacting the runway, momentum will tend to align the aircraft with the runway direction with only two wheels in contact with the runway and one can use rudder to complete the alignment before the nose wheel contacts the pavement. Once the wheels are in contact with the runway, the ailerons should still be used to counter the crosswind while on the roll out.

When you takeoff, also use aileron into the wind and avoid excessive use of the rudder. If you don't use the ailerons, the aircraft will have a greater tendency to weather vane into the wind requiring greater rudder force and the upwind side will raise with respect to the downwind side of the aircraft. The down aileron also provides additional drag to help overcome a strong crosswind weather vane.