14 CFR § 29.1193

Each cowling and engine compartment covering must be constructed and supported so that it can resist the vibration, inertia, and air loads to which it may be subjected in operation.

Cowling must meet the drainage and ventilation requirements of § 29.1187.

On rotorcraft with a diaphragm isolating the engine power section from the engine accessory section, each part of the accessory section cowling subject to flame in case of fire in the engine power section of the powerplant must—

Be fireproof; and

Meet the requirements of § 29.1191.

Each part of the cowling or engine compartment covering subject to high temperatures due to its nearness to exhaust system parts or exhaust gas impingement must be fireproof.

Each rotorcraft must—

Be designated and constructed so that no fire originating in any fire zone can enter, either through openings or by burning through external skin, any other zone or region where it would create additional hazards;

Meet the requirements of paragraph (e)(1) of this section with the landing gear retracted (if applicable); and

Have fireproof skin in areas subject to flame if a fire starts in or burns out of any designated fire zone.

A means of retention for each openable or readily removable panel, cowling, or engine or rotor drive system covering must be provided to preclude hazardous damage to rotors or critical control components in the event of—

Structural or mechanical failure of the normal retention means, unless such failure is extremely improbable; or

Fire in a fire zone, if such fire could adversely affect the normal means of retention.