33 CFR § 183.556
Plugs and fittings
August 2, 2023
§ 183.556 Plugs and fittings.
(a) A fuel system must not have a fitting for draining fuel.
(b) A plug used to service the fuel filter or strainer must have a tapered pipethread or be a screw type fitted with a locking device other than a split lock washer.