Something like that happened to me. I was setting up a new Extra. Had the plane done and ready to go. I powered it up to check the controls and noticed that I didn't have any throttle. I moved the throttle up half way, nothing. Moved it all the way up and heard the tones of motor arming!! Not expecting that, I quickly chopped the throttle. I didn't know the throttle was reversed. When I chopped the throttle, the plane took off out the door of my garage! Damn! Hit a trash can, but no damage done. I felt stupid.