Expain aircraft engines & propellers???

Modern jet engines gain efficiency by means of a high bypass ratio (ratio of air that passes around the engine core to that which is involved in combustion).

Such engines can be thought of as “ducted turboprops”. As you’d expect, they tend to be of substantial diameter.

??? I would think the SI system would use the shit-kg instead. :slight_smile:

No no no, you’re thinking of Metric. SI is really weird, and possibly French.

It’s funny, because the whole reason the Corsair has that gull-wing shape was to get clearance for the massive prop. The prop had to be big in order to use the huge quantity of horsepower that engine put out. Sure, you can use a smaller prop and spin it faster. But like others have said, that only works to a certain point. Once a certain prop speed is reached, the air no longer flows over its surface in a smooth laminar fashion and breaks up into vortices and other turbulence. The prop is no longer imparting the engines power to the air as thrust. It’s just chopping up the air. A bigger prop has more surface area so it can transfer more energy to the air than a smaller prop at the same speed.

Also, if the prop blades break the sound barrier (as was an issue with the truly weird XF-84H Thunderscreech), they do what everything else does while breaking the sound barrier: Make a sonic boom as they pass. Except unlike an airplane which does the boom and flies off into the next state, the propeller blades are remaining in roughly the same spot, a few feet in front of the pilot, the whole time.

Yeah, hearing loss was a problem for people working with/around/on the same base as the XF-84H.

Thanks for the clarifications. I get it now.