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Comment by AmVess | Hacker News Reader

The cost of this blade setup means no one will buy it. Very high cost to purchase and equally high cost to maintain for such a tiny benefit. I had a laugh at the noise reduction claim. Sure, it will reduce noise, but the open exhausts on planes are the loudest part unless some nitwit is screwing around with the pitch.

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I can't say I have the numbers to dispute this. But the loudest thing on my Cessna is not the open, 1970s era exhaust. It is definitely the prop whipping through the wind.

Is it the external noise or the cabin noise? We changed the propeller on the plane I usually fly (Ikarus C42) a couple of years ago and the new one is extremely quiet as perceived from the ground, now the engine makes more noise than the propeller. In the cockpit the noise is lower overall, but I was never able to point to the engine or to the prop from that position.

Would that change when using an electric motor?

I'd say the most favorable arrangement for noise would be a pusher configuration, with the engines close to the back of the plane instead of a tractor config on the front. This is done on the Piaggio Avanti. Not sure how well it works, but it looks like a spaceship.

Eviation electrical plane recently changed their pusher design to a tractor, but kept the engines on the back (IIRC, they started with a central big one and two auxiliary ones on the wingtips for use during takeoff).

The problem with pusher configuration is that the prop operates in turbulent air, that has already ben disturbed by going around the rest of the airplane. Whereas in tractor configuration, the prop grabs "clean" air. This is traditionally cited as the reason why pusher prop planes are louder (from the outside). In fact, one of the noisiest GA planes is the Cessna 337, which is a pull-push twin configuration.

The advantage of the Piaggio Avanti is that you can do away with the prop heat completely, as the hot exhaust from the turboprop engine simply blows on the blades. Which makes for a very nice anti-ice system.

> Which makes for a very nice anti-ice system.

Didn’t know about that. Sadly, there isn’t much hot exhaust from electric motors.

This is for cabin noise, for overall noise tractor is still better. On some airports very close to the city the overall noise is the most concerning factor, in some places you cannot operate at night because of the noise, so in the end it depends what you are looking for.

To some extent, yes. Electric motors are not completely quiet, but there are some propellers that are relatively quiet, without hard numbers it is just informed guessing.

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