Turbine Engines Which of the following factors affect the thermal efficiency of a turbine engine? 1. Turbine inlet temperature. 2. Compression ratio. 3. Ambient temperature. 4. Speed of the aircraft. 5. Turbine and compressor efficiency. 6. Altitude of the aircraft. a. 3, 4, 6. b. 1, 2, 5. c. 1, 2, 6.