14 C.F.R. § 38.3
For the purpose of showing compliance with this part, the following terms have the specified meanings:
Amphibious airplane means an airplane that is capable of takeoff and landing on both land and water. Such an airplane uses its hull or floats attached to the landing gear for takeoff and landing on water, and either extendable or fixed landing gear for takeoff and landing on land.
ICAO Annex 16, Volume III means Volume III of Annex 16 to the Convention on International Civil Aviation.
Maximum takeoff mass (MTOM) is the maximum certified takeoff mass, expressed in kilograms, for an airplane type design.
Performance model is an analytical tool (or a method) validated using corrected flight test data that can be used to determine the specific air range values for calculating the fuel efficiency metric value.
Reference geometric factor (RGF) is a non-dimensional number derived from a two-dimensional projection of the fuselage.
Specific air range (SAR) is the distance an airplane travels per unit of fuel consumed. Specific air range is expressed in kilometers per kilogram of fuel.
Subsonic means an airplane that has not been certificated under this title to exceed Mach 1 in normal operation.
Type certificated maximum passenger seating capacity means the maximum number of passenger seats that may be installed on an airplane as listed on its type certificate data sheet, regardless of the actual number of seats installed on an individual airplane.
14 C.F.R. §38.3