George Baczkowski (Flight International, 28 January-3 February) advocates disarming the yaw damper before putting the boot in on the rudder to cope with out-of-balance conditions.
I did not advocate putting a bootful of anything on an aircraft (Flight International, 7-13 January). I advocated a "push, power, rudder, roll, muscle memory" recovery flow. It is quick, easy to remember and, as a result, mitigates the surprise factor facing a crew suddenly confronted with a recalcitrant aircraft in an unusual attitude.
Speed is of the essence in this situation and interrupting that flow in locating or calling for the overhead yaw damper switch is counter-productive.
Would this flow be inhibited with yaw damper on? I believe not. The yaw dampers on Boeings have limited authority and will not override a "bootful" of rudder but mitigate it by reducing its deflection. This is transparent to the pilot in that the pedals do not move in response to damper inputs.
On the Boeing 747-400 there is no mention of the two yaw dampers on the minimum equipment list or dispatch deviation planning guide, which illustrates that its Dutch roll characteristics are benign and its damper is largely redundant. Some yaw dampers are damper than others. If they prove to be factor in the loss of the Airbus A300 near New York in November 2001 it may have design implications for Airbus.
David Connolly
Brussels, Belgium
Source: Flight International
