14 CFR § 38.11 - Fuel efficiency metric.

---
identifier: "/us/cfr/t14/s38.11"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "14 CFR § 38.11 - Fuel efficiency metric."
title_number: 14
title_name: "Aeronautics and Space"
section_number: "38.11"
section_name: "Fuel efficiency metric."
chapter_name: "FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION"
subchapter_number: "C"
subchapter_name: "AIRCRAFT"
part_number: "38"
part_name: "AIRPLANE FUEL EFFICIENCY CERTIFICATION"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "42 U.S.C. 4321  7572; 49 U.S.C. 106(g), 40113, 44701-44702, 44704; 49 CFR 1.83(c)"
regulatory_source: "Docket No. FAA-2022-0241, Amdt. No. 21-107, 89 FR 12654, Feb. 16, 2024, unless otherwise noted."
cfr_part: "38"
---


# 38.11 Fuel efficiency metric.

For each airplane subject to this part, or to determine whether a modification makes an airplane subject to this part under the change criteria of § 38.19, a fuel efficiency metric value must be calculated, using the following equation, rounded to three decimal places:

Where:

The SAR is determined in accordance with § 38.13, and the RGF is determined in accordance with § 38.15. The fuel efficiency metric value is expressed in units of kilograms of fuel consumed per kilometer.