On a wing and a....

"The Skybike was an experimental prototype microlight that integrated a Yamaha YZ80 motorcross motorbike into the trike unit which could be detached and used independently within a couple of minutes. The motorcycle had its own engine independent of the microlight engine and the pilot sat on the motorcycle seat but used his feet to steer the handle bars on the ground. The application was military following interest from the British Army. It is believed that a second prototype was also designed which had a single engine to power both the bike and aircraft propulsion. The Skybike was test flown up to 5500 feet."

Via: Microlight.org