14 CFR · Part 25
14 CFR § 25.939
Turbine engine operating characteristics.
(a)
Turbine engine operating characteristics must be investigated in flight to determine that no adverse characteristics (such as stall, surge, or flameout) are present, to a hazardous degree, during normal and emergency operation within the range of operating limitations of the airplane and of the engine.
(b)
[Reserved]
(c)
The turbine engine air inlet system may not, as a result of air flow distortion during normal operation, cause vibration harmful to the engine.
Reflects the eCFR edition current as of September 29, 2026. Retrieved from ecfr.gov on October 16, 2026.
Primary Source