Helicopter Autopilot Problems?????

[crawl55]

ok...I am in the process of creating a Bell XV-15. I am working on the cockpit and flight dynamics right now. The problem is that I am useing the helicopter flight dynamics so that I can obtain 0 airspeed for vertical flight. I have (with help from oters) tuned the aircraft to cruise at a max of 300 knots. I set the autopilot for about a 1000 ft climb and then set it at the altitude i want. When i reach the 275 knot cruise, i reduce the power and the plance starts this crazy dive/climb chase at around 2000 feet per min and i cant figure out how to fix it....does anyone know?

Thanks

Alan