40 CFR § 1030.20 - Fuel efficiency metric.

For each airplane subject to this part, including an airplane subject to the change criteria of § 1030.35, a fuel efficiency metric value must be calculated in units of kilograms of fuel consumed per kilometer using the following equation, rounded to three decimal places:

Where:

SAR = specific air range, determined in accordance with § 1030.23.

RGF = reference geometric factor, determined in accordance with § 1030.25.