FAR 23.2425 — Powerplant Operation
FAR 23.2425 requires Part 23 airplane powerplants to operate safely within limits and allow in-flight shutdown and restart by the pilot.
In Plain English
FAR 23.2425 is a Part 23 airworthiness standard that sets baseline requirements for how an airplane's powerplant (engine and related systems) must behave once installed. It applies to the airplane manufacturer during certification, but understanding it helps pilots appreciate what their engine is designed to do.
The rule has two main requirements:
- No hazardous characteristics: The installed powerplant must run safely throughout all normal and emergency operations, as long as the pilot stays within the published operating limitations for both the airplane and the engine. That means no unexpected stalls, surges, fires, or runaways when operated by the book.
- In-flight shutdown and restart capability: The pilot must be able to stop the engine in flight and then restart it within an established operational envelope (typically defined in the AFM as airspeed and altitude windows).
Operationally, this is why your POH/AFM contains an air-start procedure and engine limitations — they exist to keep you inside the envelope the manufacturer certified under this rule.
Regulation Text
14 CFR § 23.2425§ 23.2425 Powerplant operational characteristics.
(a) The installed powerplant must operate without any hazardous characteristics during normal and emergency operation within the range of operating limitations for the airplane and the engine.
(b) The pilot must have the capability to stop the powerplant in flight and restart the powerplant within an established operational envelope.
Oral Exam Questions a DPE Might Ask
Q1What does FAR 23.2425 require regarding how a Part 23 airplane's powerplant operates?
Per FAR 23.2425, the installed powerplant must operate without hazardous characteristics during normal and emergency operations within the airplane's and engine's operating limitations.
Q2Does the regulation require that you be able to shut down and restart the engine in flight?
Yes. FAR 23.2425(b) requires that the pilot have the capability to stop the powerplant in flight and restart it within an established operational envelope.
Q3Where would you find the airspeed and altitude envelope for an in-flight engine restart?
The operational envelope referenced in FAR 23.2425(b) is established by the manufacturer and published in the AFM/POH air-start or engine restart procedures.
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