4 ms·

I'd imagine that, just like in other industries, there are tons of metrics (or counter-metrics) that are also important. Some that come to mind are efficiency,

I'd imagine that, just like in other industries, there are tons of metrics (or counter-metrics) that are also important. Some that come to mind are efficiency, noise, vibration, cost, maintenance, stall characteristics, RPM requirements, weight, etc etc. From some fiddling with RC quads, I remember that increasing the number of blades does increase thrust, but at the cost of efficiency and several other parameters.

Ekaros 4y ago
My understanding as well. You increase on metric and make some other one worse. In the end it is complex process of finding some balance between these. Not that there isn't some improvements that can be made like have been done with improved materials(less weight), computer design and so on in more complex engines.
AmVess 4y ago
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.
- vlovich123 4y ago
  Would that change when using an electric motor?
  - rbanffy 4y ago
    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).
    - deleted 4y ago
      [deleted]
    - xplanephil 4y ago
      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.
      - rbanffy 4y ago
        > Which makes for a very nice anti-ice system. Didn’t know about that. Sadly, there isn’t much hot exhaust from electric motors.
    - AdrianB1 4y ago
      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.
  - AdrianB1 4y ago
    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.
- stevehawk 4y ago
  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.
  - AdrianB1 4y ago
    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.
stevehawk 4y ago
The big wins here are likely the increase in thrust and ultimately cruise speed, which makes twin props more competitive with very light jets, and the decrease in noise which may make more airports accessible to the aircraft in question due to local noise limitations. The big loss here is purchase price and maintenance price. But that's on a scale that's probably not bothering a person who can afford a brand new Beechcraft King Air or to completely refurbished a used version of the plane in the video (they quit making the Piper Navajo 30 years ago).
- MonkeyMalarky 4y ago
  If you trade efficiency for faster cruise speed, is your trip being shorter a net win for fuel costs?
  - TylerE 4y ago
    No, because drag scales with v^2. Going 10% faster requires 21% more power (and thus fuel), but only reduces trip time by 9%.
    - moloch-hai 4y ago
      AIUI, drag scales as v³, the reason doubling horsepower adds only a trivial amount of speed.
      - aidenn0 4y ago
        You are both right, there are v^2 and v^3 effects, and depending on the speed regime, one or the other will dominate.
      - AdrianB1 4y ago
        In the pilot books in my country the v2 is the most significant factor, v3 is not even mentioned in General Aviation.

Ekaros 4y ago

My understanding as well. You increase on metric and make some other one worse. In the end it is complex process of finding some balance between these. Not that there isn't some improvements that can be made like have been done with improved materials(less weight), computer design and so on in more complex engines.

AmVess 4y ago

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.

vlovich123 4y ago
Would that change when using an electric motor?
- rbanffy 4y ago
  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).
  - deleted 4y ago
    [deleted]
  - xplanephil 4y ago
    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.
    - rbanffy 4y ago
      > Which makes for a very nice anti-ice system. Didn’t know about that. Sadly, there isn’t much hot exhaust from electric motors.
  - AdrianB1 4y ago
    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.
- AdrianB1 4y ago
  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.
stevehawk 4y ago
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.
- AdrianB1 4y ago
  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.

stevehawk 4y ago

The big wins here are likely the increase in thrust and ultimately cruise speed, which makes twin props more competitive with very light jets, and the decrease in noise which may make more airports accessible to the aircraft in question due to local noise limitations. The big loss here is purchase price and maintenance price. But that's on a scale that's probably not bothering a person who can afford a brand new Beechcraft King Air or to completely refurbished a used version of the plane in the video (they quit making the Piper Navajo 30 years ago).

MonkeyMalarky 4y ago
If you trade efficiency for faster cruise speed, is your trip being shorter a net win for fuel costs?
- TylerE 4y ago
  No, because drag scales with v^2. Going 10% faster requires 21% more power (and thus fuel), but only reduces trip time by 9%.
  - moloch-hai 4y ago
    AIUI, drag scales as v³, the reason doubling horsepower adds only a trivial amount of speed.
    - aidenn0 4y ago
      You are both right, there are v^2 and v^3 effects, and depending on the speed regime, one or the other will dominate.
    - AdrianB1 4y ago
      In the pilot books in my country the v2 is the most significant factor, v3 is not even mentioned in General Aviation.