Re: 319 Dutch Roll?

Date:         23 Dec 98 03:52:36 
From:         Dieter Scholz <>
Organization: University of Applied Sciences at Hamburg
References:   1 2 3 4 5
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John M. Hunt wrote:

> ... exactly how
> difficult is it for commercial airline pilots at the bottom end of the
> coordination skill/"stick and rudder" range to make multi-hour flights
> without assistance of the yaw damper?  Is it a minor nuisance or a
> major distraction?  Is departure with an inoperative yaw damper legal?

>From the engineering side, I say:

1.) Even jets are not alike and show different levels in the "category
of effect" if yaw dampers fail.

2.) On average, I would say, loss of yaw damping is classified
"hazardous". On some aircraft loss of yaw damping can even be classified
"catastrophic". Of course on such aircraft failure of the yaw damper
system is made "extremely improbable" by building sufficient redundancy
into the system.

3.) Look into AMJ-25 §1309  ( ) or AC 25.1309 from
the FAA if you want to learn more about the relationship between
"category of effect" and "probability". Take this definition as a
starting point:

"hazardous": An effect which results in
- a large reduction in safety margins
- physical distress or a workload such that the flight crew cannot be
relied upon to perform their tasks accurately or completely, or
- serious injury to, or death of, a relatively small proportion of the