I just saw in a posting, some discussion about gyros.
Head holding vs piezo.
Can someone please explain the differences to me.
I think I understand the purpose of a heli gyro to maintain a constant and equal level for the heli. But what are the differences between the 2 if any?

TIA
Ron

Piezo can be both heading hold or non heading hold, or only non heading hold.
Non heading hold will always turn with the nose in the wind.
You also need to add REVO mix, to compensate the torque of the main rotor.
With heading hold the tail (or nose) will stay on the place you have pointed it. Even with side-wind, it will stay on the last chosen position.
So you can buy a piezo that is only non-HH or one that is both.
To activate the HH : less expensive one will be on the gyro, more expensive one will be on the transmitter.
Very good combo for the price is the Futaba GY401 with digital servo F9253.
Another version of gyro is the mechanical gyro.
So HH is only a " work mode " of a piezogyro.
This is a very limited en very simple explanation.
Hope it helps a little.
For more, check out :
http://members.telocity.com/fritzthecat/
Mario

so what is Futaba Gy401, what category does that fall into?

The GY-401 is both HH and Conventional gyro, and you adjust gain and switch between modes from your transmitter. I have just installed mine and had a first flight yesterday, and after trying many gyro combinations I ABSOLUTELY LOVE THIS ONE!!! I have never had my heli fly like this, fast backward flights were awesome, and for the first time I could go full speed sideways with the tail dead on the spot!

I recently bought the Gy401 gyro and 9253 servo. I've tried several lower cost piezo and mechanical gyros through the years, and am very happy with this combination. You'll appreciate the Heading Hold mode in holding the tail on course.