spins from coordinated flight

A "normal" turn is accomplished by splitting the lift vector, NOT by holding in yaw. Yaw should only be present in the turn dynamic during the entry into the turn and exit from the turn.

Ok, then what exactly is "yaw"? My understanding is that it is a change of direction of the longitudinal axis of the aircraft in the plane that is roughly coplanar with the wings.

Splitting the lift vector serves to change the direction of flight, but not to change the heading. To do that you need what I was calling yaw, and if you want to stay in a coordinated turn, you need to continually change the heading as you continually change the direction of flight. You would have a steady change in heading (which will include a steady yaw) with no acceleration in the yaw direction.

You seem to be defining yaw as a rotational =acceleration= of the longitudinal axis of the aircraft in the plane that is roughly coplanar with the wings.

Do I have that right?

Jose
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Jose wrote:
A "normal" turn is accomplished by splitting the lift vector, NOT by
holding in yaw. Yaw should only be present in the turn dynamic during
the entry into the turn and exit from the turn.

Ok, then what exactly is "yaw"? My understanding is that it is a change
of direction of the longitudinal axis of the aircraft in the plane that
is roughly coplanar with the wings.

Yaw, as we define the term in flight test as it relates to directional
stability is defined as moments about the VERTICAL axis, not the
longitudinal axis. These moments also relate to Yaw Angle, Yaw Rate, and
Sideslip Angle.


--
Dudley Henriques

Ok, then what exactly is "yaw"? My understanding is that it is a change of direction of the longitudinal axis of the aircraft in the plane that is roughly coplanar with the wings.

Yaw, as we define the term in flight test as it relates to directional stability is defined as moments about the VERTICAL axis, not the longitudinal axis.

Yes, that is pretty much what I said. Change in direction =of= the longitudinal axis, =in= the plane (of the wings), [(therefore) =about= the vertical axis.] I am however using "vertical" and "horizontal" as referenced to the aircraft, not the earth, thus when the aircraft pitches up, the yaw axis (as I understand it defined) would change.

Jose
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