Engineering services in the field of aircraft modification design, including power plant and propeller changes, amphibious float installations, new or modified landing gear, external stores and cameras, aerodynamic changes and modifications, structural reinforcements and cutouts, new doors and windows, electrical systems changes, battery relocations, antenna installations, special mission and restricted category and public use modifications, restoration and rebuilding, custom seating, and cabin interiors and medical system interior design; Engineering services in the field of aircraft modification design and testing in the field of single part designs for Federal Aviation Administration (FAA) parts manufacturer approval (PMA) purposes and structural static and dynamic testing; Engineering services in the field of aircraft testing in the field of turbine and piston power plant installation testing; Engineering services in the field of aircraft electrical and mechanical systems for ground and flight testing