If you look at FAR part 1, the definition of "light sport" is specifically spelled out. Among these specifications is that they must have a fixed pitch propeller, or a ground adjustable propeller. Another part of the definition is that the aircraft must have been maintained continuously within the light sport definition. So, if you have an aircraft that is not certified as a "light sport" such as "Experimental Amateur Built", that falls inside the official definition you may fly the aircraft with only an applicable pilot certificate, and a Driver license medical. However if the aircraft has at any time been equipped outside of the definition, it is no longer a light sport eligible aircraft. In the case of an aircraft certified as either ELSA or ELSA you cannot legally modify the aircraft so that it no longer meets the definition. Be especially careful when buying "Experimental Amateur Built" aircraft because I've seen a LOT of misrepresented "Light Sport" many aircraft not even currently meet the definition. This is usually found in fixed wing machines though.i see...but could you still put a constant speed prop or an adjustable prop on an elsa gyro and still be legal since its an EAB?