SPECIFIC KNOWLEDGE REQUIRED Evaluating an experimental aircraft THE WALL SEPARATING EXPERIMENTAL and standard category aircraft has become so low that pilots and aircraft owners no longer think of it as a barrier at all. Experimental airplanes account for nearly 25 percent of the roughly 100,000 single-engine piston airplanes on the U.S. aircraft registry, and amateur builders are adding about 1,000 new experimentals to the U.S. fleet annually-a figure that rivals the total for FAA-certified piston singles delivered from factories. B Y D AV E H I R S C H M A N PHOTOGRAPHY BY CHRIS ROSE aopa.org/pilot AOPA PILOT | 77http://www.aopa.org/pilot