Those advocating the use of rudder to recover from/stabilise in-flight, out of balance conditions on transport aircraft (recent Flight International correspondence), have neglected to examine the inter relationship of the yaw damper/rudder. It is the function of the yaw damper to provide the rudder with a measured response to side loads on the vertical-tail surfaces. A boot full of rudder with the yaw damper functioning will be counter productive.

If inclined to "put the boot in", then I would suggest that it would be prudent to disarm the yaw damper. On some aircraft it is a requirement that the yaw damper is disarmed for take-off, and landing.

Having lost both yaw dampers on an A300 while operating in continuous moderate turbulence, I can vouch that recovery from the subsequent Dutch roll was easily effected using standard procedures, no rudder, with an uneventful return to base.

George Baczkowski Swardeston, Norfolk, UK

Source: Flight International