It is simpler than you can imagine, it's just two steps.
1- Export your perspective view by clicking onto Tools > Save 3D win as PNG spin animation. Choose your desired FOV and camera height as usual on that window, then AC3D will save a 360° spin of your model in a specified directory.
2- Use a freeware or payware application to easily compose the Quicktime VR, there's plenty of them around. One is called Spinimage DV another is VR worx.
This technique best fits for a 3D object quicktime, but creating a full navigating environment should be as simple as this one since those apps can glue single exported PNGs into a system of cubes. That should be done by clicking onto Tools > Save 3D win as PNG.
You can see my results on
http://www.xplaneshop.com/mov/AW139_qtvr.mov