Thecna2 t1_irphtnw wrote on October 10, 2022 at 1:14 AM

Reply to comment by GmeGoBrrr123 in TIL that passenger jet engines produce most of their thrust from fan at the front, not from the jet exhaust, and that this is called a high-bypass engine. by Rilot

This change from Low Bypass Turbofan to High Bypass occurred in the 80s. Engines prior to this point provided all/most of their thrust from the central exhaust core.

The change occurred mainly because of fuel efficiency but it did require changes. The newer type have much larger fans than the old type and thus the engines on the wings will get closer to the ground meaning some design changes (higher wings/mounts).

The fan creates the thrust because it is very big and running very fast, like a prop. No real other reason.

I worked on the old style engines as they changed over to the new style.

p33k4y t1_irqpdit wrote on October 10, 2022 at 9:16 AM

>This change from Low Bypass Turbofan to High Bypass occurred in the 80s.

1970s:

Pratt & Whitney JT9D on the Boeing 747-100 (in service 1970)
GE TF39 on the Lockheed C-5 Galaxy (1970)
GE CF6 on the McDonnell Douglas DC-10 (1971)

The CFM56 also started production in 1974 but did not enter commercial service until 1982.