{"data":{"id":"us/14-cfr-29.939","jurisdiction":"us","citation":"14 CFR 29.939","heading":"Turbine engine operating characteristics.","body":"(a) Turbine engine operating characteristics must be investigated in flight to determine that no adverse characteristics (such as stall, surge, of flameout) are present, to a hazardous degree, during normal and emergency operation within the range of operating limitations of the rotorcraft and of the engine.\n(b) The turbine engine air inlet system may not, as a result of airflow distortion during normal operation, cause vibration harmful to the engine.\n(c) For governor-controlled engines, it must be shown that there exists no hazardous torsional instability of the drive system associated with critical combinations of power, rotational speed, and control displacement.","path":["Title 14—Aeronautics and Space","CHAPTER I—FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION","SUBCHAPTER C—AIRCRAFT","PART 29—AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT","Subpart E—Powerplant"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-14.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:24:20Z","sha256":"b045e4b4e6ade64b2807ef01cf182483caaa2363d092abbde73ceb3e3a9d6ffd","source_id":"us-cfr","stale":true,"prev":"us/14-cfr-29.935","next":"us/14-cfr-29.951"},"notice":"GroundRules: Original legal text. Not legal advice."}