(Replying to PARENT post)

It would be really interesting to see what his attempts with aircraft amounted to. Propeller tip induced turbulence is a non-trivial portion of what makes general aviation (GA) very loud. If we could make the aircraft less loud without significantly reducing their performance perhaps GA would be more amenable (along with other changes like moving eventually to electric power plants). As it stands right now the general public isn't much of a fan of GA and there is always strong push-back to creation of GA airfields which I think is a shame. The joy of flying shouldn't be limited to commercial pilots and yet increasingly here in Australia that is the way it is.

Things are very different in the US because their GA culture is older, more powerful and protected by the FAA and pilots associations.

👤jpgvm🕑3y🔼0🗨️0

(Replying to PARENT post)

In Europe where noise is a bigger issue you often see four blade props on small single engine planes. That, combined with mufflers make a huge difference in overall noise. It costs on the order of 3% of performance.
👤cameldrv🕑3y🔼0🗨️0

(Replying to PARENT post)

I'm guessing the stresses on the propellers at high rpms typical for planes might be an issue. The issue with plane noise is the tip of the propeller breaking the speed of sound. This is what generates a lot of the noise. Having a lot of mass there might be an issue. The prop might rip itself apart. Rpms in water are a lot lower so, it's less of an issue there.
👤jillesvangurp🕑3y🔼0🗨️0

(Replying to PARENT post)

The Thunderscreech had a supersonic propeller.

https://en.m.wikipedia.org/wiki/Republic_XF-84H_Thunderscree...

Unsurprisingly it was noisy.

👤DrBazza🕑3y🔼0🗨️0

(Replying to PARENT post)

Another factor is that lots of small GA airplanes are direct drive, and so need to run at high RPM at takeoff to produce full climb power. Geared powerplants like Rotax can reduce the overall tip speed here, and constant speed props can help to some extent. Turbine props need to be geared and tend to run lower tip speeds, so small GA is actually having an outsized negative impact here.
👤ericpauley🕑3y🔼0🗨️0

(Replying to PARENT post)

Part of the issue is that a lot of propellers in GA are, well, simple.

We do have better designs available, but very fast you end up with either very complex manufacture (and thus price) for special aeroelastic propeller, somewhat less expensive automatically adjustable props, better engines (hello recertification! the big cost killer and what made G100UL so important). I do not know if scimitar prop blades require adjustable mechanism, but wouldn't surprise me. And then there's how to fit scimitar blade on some airplanes.

So unfortunately non-trivial even when everyone involved is all for change, because change costs a lot.

👤p_l🕑3y🔼0🗨️0

(Replying to PARENT post)

This propeller push the water/air inward again, so I guess it would most logical to place it in the back of an airplane?

Or move it to the back of the wing.

👤punnerud🕑3y🔼0🗨️0