HI,
What make of TX are you using? In terms of Gyro mode there is a differance between JR and Futaba.
In JR, over 50% is Heading Hold, below is normal (or RATE) mode. BUT, on Futaba you have a full range of 0 - 100 in both heading hold and in rate mode, there is an extra section on the display that tells you which mode you are in.
Norm is normal or RATE mode, and AVCS is their identification that you are in Heading Hold mode.
If you are in the normal mode the tail can swing when you apply power unless you add some mixing, but in HH mode the tail should remain steady. I would suggest if you have a Futaba TX you check this.
Hope this helps,