Re: spins from coordinated flight

Stefan wrote:
> Dudley Henriques schrieb:
> 
>> Yaw should only be present in the turn dynamic during the entry into 
>> the turn and exit from the turn. Once stabilized in the turn, there 
>> should be no yaw present.
> 
> I don't agree. A coordinated turn is *always* a turn around all three 
> axes. (The only exception is a turn with a 90 degrees bank.) You can 
> easily demonstrate this by "hand-flying" a toy airplane.


Axis isn't really used in this way. You will notice if you move your toy 
airplane that the axis system remains in place and moves with the 
aircraft centered on the aircraft's cg.

To define turn using axis reference is not the best way to explain turn 
since once established in a stable turn there should be no movement on 
the airplane's axis system. The axis system references the lines 
crossing through the aircraft's Cg and are used to define movement and 
moment on each axis. The axis system moves in place with the aircraft 
and never deviates from it's center point through the cg.
There is movement on the longitudinal axis in roll as the airplane is 
rolled into and out of the turn, and movement as well on the lateral 
axis in pitch as angle of attack is increased to compensate for the 
split in the lift vector. There is movement on the Vertical axis as 
rudder is used to compensate for adverse yaw both during and exiting the 
turn, but once established in a coordinated turn, (I'm using medium 
banked turn here for easy reference as under bank  and over bank in 
shallow and steep turns cause in turn axis changes complicating the 
situation a bit) all movement on the aircraft's axis should be stable.

The proper way to define turn as relates to  change in direction is to 
define the change in the velocity vector as relates to heading change 
not as a change on or around the axis of the aircraft.


-- 
Dudley Henriques