The pilot-in-command’s failure to release the parking brake before attempting to initiate the takeoff, which produced an unexpected retarding force and airplane-nose-down pitching moment that prevented the airplane from becoming airborne within the takeoff distance available and not before the end of the airport terrain. Contributing to the accident were the airplane’s lack of a warning that the parking brake was not fully released and the Federal Aviation Administration’s process for certification of a derivative aircraft that did not identify the need for such an indication.