StacksVerified U.S. regulatory reference

14 CFR §121.251

Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
Unless equivalent protection can be shown by other means, a diaphragm that complies with § 121.247 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.