14 CFR §38.13

1. (a)For each airplane subject to this part, the SAR of an airplane must be determined by either:
   1. (1)Direct flight test measurements; or
   2. (2)Using a performance model that is:
      1. (i)Validated by actual SAR flight test data; and
      2. (ii)Approved by the FAA before any SAR calculations are submitted.
2. (b)For the airplane model, establish a 1/SAR value at each of the following reference airplane masses:
   1. (1)High gross mass: 92 percent MTOM.
   2. (2)Low gross mass: (0.45 * MTOM) + (0.63 * (MTOM^0.924)).
   3. (3)Mid gross mass: simple arithmetic average of high gross mass and low gross mass.
3. (c)To obtain (1/SAR)avg as required to determine the fuel efficiency metric value described in § 38.11, calculate the average of the three 1/SAR values described in paragraph (b) of this section. Do not include auxiliary power units in any 1/SAR calculation.
4. (d)All determinations made under this section must be made in accordance with the procedures applicable to SAR as described in appendix A to this part.