This is an NXT-powered Moving Minifig Machine Module. Here is a short (30 second presentation video):
  The module is modelled after the ride in the classic game Theme Park (just as my previous threads with Bouncy Castle and Theme Park Fountain).   The NXT uses 3 motors: - One for the track, where a switch ensures the outer track always runs forward - One to lift the planes (this also rotates the sun) - One to rotate the tower The airplanes and tower have gone through many iterations before I could find a balance that was both functional and didn't look too bad. This is an early version of he tower using linear actuators:
Unfortunately I had to remove the inner wings of the airplanes for this version, so I changed the design to this: Unfortunately that design was both too tall and unreliable. I ended up with the final design without using linear actuators: And a close-up of the mechanism: A sensor is used to detect when a plane is ready to be loaded or unloaded, and a light sensor is able to detect minifigs: The doors of the airplanes open and close using the gray bars hitting a vertical bar next to the entrance: Adding it all up, and this has become my most complicated MMM module thus far   In this long video (almost 10 minutes!) I go into details of how the module works, how it self-calibrates, and how to access all of the mechanical components quickly in case it is being used at an event: I hope you enjoy this kind of creations, and that MMM can become a success at events.