Be Careful Near Vmin
In the EC-135 you have to be careful when operating in any altitude mode at airspeeds near Vmin. At low power as the aircraft approaches bucket airspeed the cyclic will unsuccessfully attempt to hold altitude. Near or below the bucket airspeed the aircraft may continue to descend. There is no aural warning of this condition as the autopilot is functioning properly. The Alt enunciator on the PFD will flash. This condition may have contributed to a collision with the surface in Florida a few years back. If you want to demonstrate this just engage Alt hold and slow the aircraft with collective. You will see that the aircraft will very slowly and insidiously begin a descent while still above Vmin.