allergic2Luxembourg t1_irq5k04 wrote on October 10, 2022 at 4:45 AM

Reply to comment by InevitableRip8968 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

That's an oversimplification. Turboprops are more efficient at certain altitudes and Mach numbers, and jet engines at others. Thus why turboprops are used in shorter-range applications and jet engines in longer-range. The industry is most certainly choosing the right engine for efficiency as one of the major driving factors (though weight is also considered).

LazerWolfe53 t1_irqnzjc wrote on October 10, 2022 at 8:54 AM

I feel like altitude is missing from most of these conversations. IIRC the high bypass jet engines get most of their thrust from the jet at high altitude.

IvorTheEngine t1_irqpkyt wrote on October 10, 2022 at 9:19 AM

And flying higher means the air is thinner, so there's less drag. So even if the engine is less efficient, the overall flight can be more efficient.