Oil valves

This regulation sets requirements for oil valves on aircraft operating under Part 121 (air carriers). Each oil valve must meet the specifications in §121.257, have clear positive stops or indexing in both "on" and "off" positions so pilots know the valve's status, and be mounted so that operational forces or flight loads don't stress the attached oil lines.

Critically, the regulation addresses a safety concern with propeller-equipped aircraft: shutting off oil flow must not prevent the crew from feathering the propeller (rotating the blades to minimize drag). This is essential because a feathered propeller on a failed engine significantly improves aircraft performance and safety. If an oil shutoff valve design would prevent feathering, the manufacturer must incorporate alternative safety provisions to protect against engine failure scenarios. This ensures crews retain control options during emergencies regardless of oil system configuration.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*