14 CFR § 27.1193

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.

There must be means for rapid and complete drainage of each part of the cowling or engine compartment in the normal ground and flight attitudes.

No drain may discharge where it might cause a fire hazard.

Each cowling and engine compartment covering must be at least fire resistant.

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.

A means of retaining 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.