Section 1030.23 - Specific air range (SAR)(a) For each airplane subject to this part the SAR of an airplane must be determined by either:(1) Direct flight test measurements; or(2) Using a performance model that is:(i) Validated by actual SAR flight test data; and(ii) Approved by the FAA before any SAR calculations are made.(b) For each airplane model, establish a 1/SAR value at each of the following reference airplane masses: (1) High gross mass: 92 percent maximum takeoff mass (MTOM).(2) Low gross mass: (0.45 * MTOM) + (0.63 * (MTOM^0.924)).(3) Mid gross mass: Simple arithmetic average of high gross mass and low gross mass.(c) Calculate the average of the three 1/SAR values described in paragraph (b) of this section to calculate the fuel efficiency metric value in § 1030.20 . Do not include auxiliary power units in any 1/SAR calculation.(d) All determinations under this section must be made according to the procedures applicable to SAR in Paragraphs 2.5 and 2.6 of ICAO Annex 16, Volume III and Appendix 1 of ICAO Annex 16, Volume III (incorporated by reference in § 1030.110 ). 86 FR 2172 , Jan. 11, 2021; 86 FR 52416 , Sept. 21, 2021 86 FR 2171, 1/11/2021; 86 FR 52416, 9/21/2021