I've been having a bit of fun today doing the math to fly a Lego helicopter I got from Google's Sketchup 3D Warehouse, so I thought I'd share the file. The file's 11MB because there's some tex for the background mountains. I made a short video to show how it works
scene https://www.dropbox.com/s/tcnzx19uqtyucg9/helicopter.zip?dl=1
there's a bit of info in the XPresso remarks.