21. Flammable fluids -
(a) Engine compartment. C-46 engine compartments which conform to the type design and which comply with all applicable airworthiness directives meet the requirements of § 121.255.
(b) Combustion heater compartment. C-46 combustion heater compartments which conform to type design and which meet all the requirements of AD-49-18-1 or an FAA approved equivalent meet the requirements of § 121.255.