What is the overall efficiency of a turbofan engine?
Mesun – I do not know what efficiency figures you are seeking – As pilot, and with a mere interest to compare, I knew a few numbers. All that through my airline career – from 1969 through 2008. I recall my “straight-pipe” turbojet engines JT4A – old 707-300s Remembering they had a SFC specific fuel consumption of .70 – Meaning it took .70 of a lb of fuel flow to produce 1 lb of thrust. These engines had 17,500 lbs thrust on takeoff… The SFC improved drastically with the turbofans. The newer 707-320B/C had the JT3D engines with 18,000 thrust. And their SFC dropped to .53 – And the higher bypass ratio further decreased the SFC. The JT9D in the 747-200/300 are at a 37.5 SFC – I know it took 19,500 lbs fuel flow for 52,000 lbs thrust at sea level As pilot, this is as far as I looked at efficiency engine numbers. I am not an aeronautical engineer – just was interest.
