14 C.F.R. § 25.973 Fuel tank filler connection.
Title 14 - Aeronautics and Space
Each fuel tank filler connection must prevent the entrance of fuel into any part of the airplane other than the tank itself. In addition— (a) [Reserved] (b) Each recessed filler connection that can retain any appreciable quantity of fuel must have a drain that discharges clear of each part of the airplane; (c) Each filler cap must provide a fuel-tight seal; and (d) Each fuel filling point must have a provision for electrically bonding the airplane to ground fueling equipment. [Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by Amdt. 25–40, 42 FR 15043, Mar. 17, 1977; Amdt. 25–72, 55 FR 29785, July 20, 1990; Amdt. 25–115, 69 FR 40527, July 2, 2004]
Title 14: Aeronautics and Space
PART 25—AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES
Subpart E—Powerplant
Fuel System
§ 25.973 Fuel tank filler connection.