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