This paper presents a novel autopilot for a 3D helicopter. From desired trajectories defined by the user for elevation and travel angles, the autopilot is computing the desired trajectory of the pitch angle. Furthermore, the autopilot allows to decouple the system and to define "virtual" inputs in order to separately design controllers for each attitude angle. Travel and elevation controllers are based on adaptive version of sliding mode control: this class of controllers keeps the robustness feature of sliding mode while reducing the well- known drawback of such control approach, the chattering, thanks to the online adaptation of the controller gain. The proposed autopilot is evaluated on an experimental set-up.