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Plane Oscillation

Tue Aug 29, 2006 12:58 am

This will probably be one and only post so here goes.
When flying back to YYZ on a Mexicana A319 I became aware of the aircraft gently oscillating around the main longitudinal axis.I only noticed it when looking out the window at the horizon.and observed the wing going up and down.This continued over about 4 hours of the flight.In all my 40 years of flying I have never observed this before.Unfortunately I have not flown since(snow not due for about 2months then its off to BKK) when I will be observing
this again.I am hoping one of the flight crew members can explain this .
Thank you in advance for any replies.
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RE: Plane Oscillation

Tue Aug 29, 2006 1:42 am

Never seen it happen on the Airbus, but the 747 Classic does it all the time. Generally, it wallows around like a walrus anyway in cruise! No idea why, probably just the old tech in the autopilot.
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RE: Plane Oscillation

Tue Aug 29, 2006 2:02 am

Sounds a little like dutch roll, but not really. You wouldn't expect a whole lot of dutch roll on an a319, especially if the yaw damers were working correctly. Did you notice the plane yawing also? If so, it was probably dutch roll, maybe they had a MEL for a yaw damper. Otherwise, nothing jumps to mind . . .
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RE: Plane Oscillation

Tue Aug 29, 2006 5:18 am

I would say the ailerons are out of rig. This causes the autopilot to constantly reposition them. The autopilot lowers the aileron that is too high, to raise the wing. However, this makes the opposite aileron to low, so it raises it to lower the wing, that will go on until the system is rigged correctly.