A month or so ago, during a game of Squadron Strike, my opponent had his ship do a 180 degrees flip.  When he went to allocate his shots, he was surprised to learn that in addition to flipping 180 degrees, his ship had also rolled 90 degrees.

Initial Position

Expected Position	Actual Position

There is a pair of culprits that cause this "phantom" roll.  The first is the Green Ring.  Unlike the Amber and Blue Rings, the Green Ring's windows are 60 degrees instead of 30 degrees.  This causes pivots coming from a hex corner to rotate the ship left or right in order to face a hex edge when the Nose enters the Green Ring.  This will be shown in more detail later.

The other culprit is the fact that Squadron Strike uses 2 movement values (pivot and roll) for 3 axes of freedom (pitch, yaw, and roll).

Roll is straight forward. The Nose stays still and the Top, Bottom, and Wing markers move.

Roll Example 

Pivots are not as straight-forward as they combine pitch and yaw. This can result in all 6 symbols potentially moving at once.

Pivot Example 

The rules for how to move all 6 symbols are a bit vague.  The rules depend upon humans making a intuitive leap to figure out where things go.  In general, this is not a problem as player will know the orientation that they want to end up in and any procedural errors that occur typically do not impact the game.

However, software can not make intuitive guesses nor can they read the mind of their users to figure out what the final orientation should be.  Therefore apps, like AVID Assistant 2, use a series of rules to determine how the symbols should move during a pivot.  

I'm not going to go over the algorithm that AVID Assistant 2 uses as it would make little sense for humans to follow.  

The two things to understand are the "Great Circle" and that pivots are plotted out on a window by window basis.  

To refresh: A Great Circle in the series of windows that is exactly 3 windows away from a pair of symbols (Nose-Aft, Top-Bottom, Right-Left).  The 4 other symbols will be found in this Great Circle.  For example, the symbols for the Top, Bottom, Left and Right Wings will be found in the Nose-Aft Great Circle.

180 Flip with no Roll	180 Flip with 90 degree "virtual" roll.
The initial position for both sides.  The key point is that this only applies when starting with the nose facing a Hex Corner.
A very straight forward movement. Both the Nose and Top moving along the Right-Left Wing Great Circle.
Here is Culprit #1: Entering into the Green Ring from a Hex Corner.  As you can see, the entire ship had to rotate to the right by 30 degrees.
The "error" from moving into the Green Ring continues.  In "reality" the Top would be in D/E, but as the ship had to rotate to enter the Green Ring, it ended up in E instead. This is also a common spot for "human error" when doing this manually.  If a player has a pivot of 2+, they would just skip over the Green right and drawn their Nose straight up with the Top in D/E.
Here is where the two plots diverge.
This option moves the Nose along the Right-Left Great Circle towards the Top. As the Nose is following along one of the Great Circles, only the 4 symbols on the Right-Left Great Circle move.	This option moves away from the Top, towards the Right Wing.  The Nose is moving 60 degrees away from the direction of the Top by moving in direction D.   As the Nose is not following along one of the Great Circles, all 6 symbols move.
As the Pivot exits the Green Ring, it rotates back 30 degrees.	As the Pivot exits the Green Ring, it rotates back 30 degrees.
The Pivot Finishes.	The Pivot Finishes.