Lake Amphibians by their nature is technically a plane when airborne. Once they are in the water their are consider a water vessel. That is why amphibs have both FAA call letters and CG bow numbers on the front. Once the amphib lands it must obey all boating rules including life vest, paddle and other safety devices requires by law. This has always been a touchy subject with MP jurisdiction. In the case for Pickeral Pond, if an amphib lands, it is a boat and MP may or may not consider it a sea plane because it is not by law. That is why the speed limit rule in Winnipesaukee will be tested in this matter. During the 'stepping' out of the water to airspace and vice versa, it is a gray area in which both FAA and MP will argue that it is one or the other. I would love to see how this 'play' if it ever enters court.
