14 CFR · Part 27
14 CFR § 27.969
Fuel tank expansion space.
Each fuel tank or each group of fuel tanks with interconnected vent systems must have an expansion space of not less than 2 percent of the tank capacity. It must be impossible to fill the fuel tank expansion space inadvertently with the rotorcraft in the normal ground attitude.
Reflects the eCFR edition current as of September 29, 2026. Retrieved from ecfr.gov on October 16, 2026.
Primary Source