Scary Crosswind Takeoff in a Skycatcher

[dell30rb]

When you takeoff in a crosswind, the airflow is not straight over the fuselage when you are rolling down the runway. The airplane wants to turn into the wind even though the wings are level. Thats why it will turn into the wind and depart the runway if you let off the crosswind rudder correction during your takeoff roll.

Note that an actual weathervane looks like an airplane with no wings for lift. Because of the shape of it (with vertical stabilizer) the weathervane always points into the apparent wind, making the apparent wind angle zero.

Starting at 0mph you might have an apparent wind at a 90 degree angle to the airplane (direct right xwind) as you accelerate the apparent wind speed increases and the angle aligns more with the direction of travel. So that when you take off the apparent wind angle might have decreased to a much smaller angle, say 3-4 degrees off the nose of the airplane. With no rudder input (forget prop torque for a minute) the airplane is basically a big weathervane and wants to point directly into the apparent wind, or 3-4 degrees to the right of the centerline track. However by holding the rudder in during the takeoff roll to counteract the crosswind, you are biasing your weathervane to point a few degrees to the left instead of into the apparent wind, so that you can track the centerline. When you lift off, you no longer need to align the plane with the centerline, so you remove the crosswind rudder correction and the airplane 'weathervanes" into the apparent wind, making the apparent wind angle zero.

The DA20 I trained in and the bonanza I now drive handle very similarly: turn ailerons into the wind and right rudder on takeoff. Anything else while wheels are on the ground and you will be calling an insurance adjuster.

If you are taking off in a stiff enough crosswind from the right, it will overcome the prop torque and you'll need left rudder on the takeoff roll instead.

 

[RoscoeT]

Crude, but even with a hurricane-force "crosswind", I did not see any weathervaning tendency in the time the model was aloft.

You'll never convince some folks. LOL. Getting people to correct their thoughts on the dreaded x-wind/side/forward slip/weathervane topic is like asking them to renounce their religion.

 

[brian]]

Ok, I'll buy it - I do agree that the rudder is what is used to keep you pointed down the runway - regardless of required input. Although I really can't think of a time when I've had to use left rudder to say on the runway during takeoff.