14 C.F.R. § 125.149 Engine accessory section diaphragm.
Title 14 - Aeronautics and Space
Unless equivalent protection can be shown by other means, a diaphragm that complies with §125.145 must be provided on air-cooled engines to isolate the engine power section and all parts of the exhaust system from the engine accessory compartment.
Title 14: Aeronautics and Space
PART 125—CERTIFICATION AND OPERATIONS: AIRPLANES HAVING A SEATING CAPACITY OF 20 OR MORE PASSENGERS OR A MAXIMUM PAYLOAD CAPACITY OF 6,000 POUNDS OR MORE; AND RULES GOVERNING PERSONS ON BOARD SUCH AIRCRAFT
Subpart E—Special Airworthiness Requirements
§ 125.149 Engine accessory section diaphragm.