What is Thrust Specific Fuel Consumption (TSFC) and what affects it?

TSFC measures engine fuel efficiency as fuel flow rate divided by thrust produced (lb/hr/lb or kg/hr/N). Lower TSFC means better efficiency. Typical values range from 0.3-0.4 for modern turbofans to 0.8-1.0 for turbojets with afterburner. Factors affecting TSFC include: Overall pressure ratio and turbine inlet temperature (cycle efficiency), Bypass ratio (propulsive efficiency), Component efficiencies, Flight Mach number and altitude, and Throttle setting (optimum at high power). TSFC improves with altitude due to lower temperature and better propulsive efficiency, important for long-range cruise optimization.