Re: Oscillation during flight

From:         mike <>
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Date:         07 Jul 96 14:15:56 
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Bill Hensley <> wrote:
>Hi, during a recent ATL-DFW flight, the 727-223 I was riding began a series
>of oscillations of increasing size.  The first was about 2-3 degrees and the
>10th was about 15-20 degrees.  I am a bit uncertain of the exact values as
>I had no way of precisely measuring the activity.  A second set of oscillations
>of lesser intensity and duration occurred about 2 minutes later.  I was sitting
>in the very back of the aircraft during this event.  No wx was nearby,
>although you sould see some TCU off in the distance to the north.  This
>occurred about 45 min after takeoff, somewhere over MS/AL.  The ride was
>totally smooth otherwise.

Dear Mr Hensley, et al,

I have a question.  Was the oscillation in the longitudinal axis.  That
is, was the plane yawing left and right?

My first impression was that the crew could have been "playing" with the
yaw dampener, or had a failure with it.  However, 20 degrees of yaw is
quite extreme.

I say "playing", because the weather and cruise conditions that you
described do have a tendency to be boring to the crew.  Its at times like
this that a "what if" or "how does this thing really work" discussion
might take place in the cockpit.

The crew of a (TWA?) 727 was sort of "playing" with the flaps at cruise
to milk out a little bit better fuel economy.  They did a barrel roll
before recovering, losing 10's of thousands of feet of altitude in the
process.  Not a boring flight at that point.

Mike Weller