FAA Aviation Mechanic Powerplant (AMP)Turbine EnginesHard
A turbojet engine burns fuel at a rate of 8,000 lb/hr while producing 4,000 lb of net thrust. What is the engine's thrust specific fuel consumption (TSFC)?
- A4.0 lb/hr/lb thrust
- B0.5 lb/hr/lb thrust
- C8,000 lb/hr/lb thrust
- D2.0 lb/hr/lb thrust
Show answer & explanationAnswer & explanation
Correct answer: D. 2.0 lb/hr/lb thrust
TSFC = fuel flow ÷ net thrust = 8,000 lb/hr ÷ 4,000 lb = 2.0 lb of fuel per hour for each pound of thrust produced. This value expresses engine fuel efficiency, with lower TSFC indicating better efficiency.
Why the other options are wrong
- A. This would result from doubling the correct answer, not from the actual formula.
- B. This results from inverting the calculation (thrust ÷ fuel flow) instead of fuel flow ÷ thrust.
- C. This is simply the fuel flow value with no division performed.
Thrust Specific Fuel Consumption (TSFC)
A measure of turbine engine fuel efficiency calculated as fuel flow divided by net thrust produced.
- Units are lb fuel/hr per lb of thrust
- Lower TSFC = more efficient engine
- Used to compare engines of different thrust classes
Memory trick: TSFC: how much fuel it costs to buy one pound of push.