N9373M

I was taught that a Dutch Roll was keeping the nose on a fixed point (water tower, etc), rolling the plane 20' left/right and to use the rudder to keep the nose on the point in space .

After reading the recent thread on the KC-135 mishap (with oscillations, yaw damper, vert stab failure, etc) it's obvious I was not doing DR.

What was the maneuver I was doing called? (poorly I might add). You had to lead/lag the rudder input to keep the nose oriented. Also, should the ball be centered?

Tak

ClarenceOver

With the designee that i used it meant you passed your checkride.

JamesNoBrakes

Uncoordinated roll-in/out.

e6bpilot

Oscillations of yaw coupled with roll. Pretty common in swept wing aircraft. If left unchecked, it can lead to air loads that exceed design parameters of the vertical stabilizer.
We practice recoveries in the sim and check the yaw dampers by turning them off, imparting Dutch roll, and turning then on on our functional check flights. It will get your attention in a hurry, that is for sure.

atpcliff

It's a pastry u buy in AMS. Or type of pastry u buy elsewhere, that is prepared by a baker from Holland.

JamesNoBrakes

But that's not important now.

hypoxia

As one wing rises (increases its bank) it creates lift, when lift is increased, induced drag increases, when induced drag increases, the wing banks down and moves rearward (the nose yaws or "adverse yaw") the opposite wing banks upward and forward and the cycle repeats itself into a dutch roll with an increase in amplitude which = "no bueno" .... at least in the jets I fly!

To get out of it you tap a little aileron into the raised/rising wing. Yaw Dampers should prevent this phenomenon from happening. The airlines should give you this training in the simulator. Disclaimer: Follow the aircraft manufacturers guidelines and or company procedures!!!

Feel free to chime in!

JamesNoBrakes

Excellent simple explanation, and swept wings greatly contribute to this as the advancing wing will effectively become "less swept" and generate more drag and lift, allowing the cycle to repeat as it then rises and gets pulled back.

On the other topic:

The "roll in and keep the nose on a point" thing has been perpetuated for a long time as a way to be "coordinated", but it's actually the opposite of this. At 1° of bank, the airplane should be turning. At 10° it should be turning faster, and at 30, faster yet. As SOON as you are in a bank, the nose should be moving in the direction you are banking, slowly at first, then faster as your bank is higher. What it should NOT do is remain "on a point" until you reach your desired bank, and then suddenly "start turning/moving" on the horizon. For some reason this has been taught over the years as "how to enter a turn coordinated", when it's actually the opposite, keeping the nose on a point may be a good exercise in the ability to "make" the aircraft point where you want and keep heading alignment during landing, but it ain't no "coordinated" turn.

Atomized

Roll due to yaw.

N9373M

thanks for all the input (even the semi funny/sarcastic ones)

It's was a maneuver I had never done before, and was part of a club checkout 20+ years ago shortly after getting my PPL. I had forgotten about it until the KC-135 thread. I was always perplexed as to why the checker-outer said to keep the ball centered (bad memory?). Perhaps it was a language problem - he was retired Luftwaffe and I was too stupid to learn/ask from him.