Rainbowdash crash and broke her both wings and gets a concussion. She is gone for months and thats mean none takes care off the weather. Fluttershy tries first but she is to slow and sometimes she stays at one place in one hour to look at birds. Twilight has yust read a book about Technology. So she is building a robot she calls RoboDash.
That will replace Rainbow Dash until she comes back. But after a while the Robot is losing the controll and only Rainbowdash can stop it....