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I'm calling bullshit. Compare it to the TBM900 which has a 900hp turbine engine and vastly similar layout. There is no way they can go 60 knots faster on 300 le

I'm calling bullshit. Compare it to the TBM900 which has a 900hp turbine engine and vastly similar layout. There is no way they can go 60 knots faster on 300 less horse power. And even if they somehow pull off that trick, that short skinny wing will make the MU-2 feel like a safe family minivan.

asdfadsfgfdda 6y ago
The layout/payload may be similar to a TBM, but I'm guessing the wing loading and cruise altitude will be higher. So it's definitely feasible to go faster on less power.
- VBprogrammer 6y ago
  Aerodynamic drag is a square relation so the difference in drag there is about 40%. With 65% of the power. I think occam's razor applies here. Either the aerodynamics of reasonably modern aircraft designs leave a huge amount on the table or this startup is telling fibs. There are other reasons to be suspicious, modern diesel engines rely on a large amount of turbo charging to achieve sea level rated power, it's difficult to believe they are able to maintain this rated power to 50,000ft or 60,000ft. (In the case of the TBM the engine is actually capable of about 1300hp at sea level but is "flat rated" to what it can maintain at altitude). Finally, almost all high altitude aircraft have long wings (think the U2 as that is not far from what we are talking about here). Adding longer wings typically increases high altitude performance (there are aircraft with model variants where the wings got longer, like the twin commander). This aircraft appears to have borrowed a couple of surfboards.
  - Tuna-Fish 6y ago
    > I think occam's razor applies here. Either the aerodynamics of reasonably modern aircraft designs leave a huge amount on the table or this startup is telling fibs. Aerodynamics of reasonably modern aircraft designs do leave a huge amount on the table. Generally for good reasons, though. The 500L is clearly almost entirely a laminar-flow design, unlike conventional aircraft (including the one you linked). Experience from gliders have shown that a small laminar flow design like this can have less than a third of the drag of what a conventionally shaped design of roughly similar size. There are two major downsides to designing like this: Firstly, the shape is entirely determined by physics, leaving very little wiggle room for manufacturing or practical concerns. Without modern composites, cost-effectively manufacturing the frame is impractical. Secondly, the great drag properties are very dependent on the properties of the skin of the aircraft. Laminar-flow gliders can have their glide ratios halved after accumulating a few too many insects on the leading edge. If you want to fly very high, (as this plane seems to want to), better hope you have an amazing de-icing system, or even a very small amount of ice will trash your aerodynamics.
    - VBprogrammer 6y ago
      Don't forget low speed handling and stall characteristics. There are so many places where the practically of this aircraft would fall down. Good luck fitting deicing boots to a wing which needs to be kept so clean polishing it makes a difference. Also, good luck trying to get an clearence to climb to 60,000ft around any busy international airspace. Regardless of any aerodynamics miracles this aircraft pulls off I'm sure we agree that it's climb performance will be distinctly average. That means it's going to take well over an hour to get up there. 20 mins or more could be spent in the RVSM band (FL280+) where most of the airliners are, expect to be vectored all over the sky while this happens. This is already a problem in something like the CJ2 which like to cruise higher than the airliners but aren't quite as fast. It's climb performance is considerably better than you would expect from this aircraft.
jillesvangurp 6y ago
If they reduce drag, which is exactly what they are claiming to have achieved, that would reduce the amount of horse power needed to overcome that drag. Less HP translates into better fuel economy. Basically this plane has the engine mounted on the back, which means center of gravity and wing position are quite a bit different. The nose cone looks very streamlined and crucially the wings are in front of the vortex produced by the prop. I'm guessing that that adds up to a bit of reduction in drag. The reason many planes have the engines mounted on the other side probably have to do with things like cooling, engine size, and other practical concerns.
- VBprogrammer 6y ago
  They are claiming improvements across almost all areas. If it flew as fast and as far as the competition on 50% less fuel, that would be amazing. If it flew 60 knots faster in the same fuel and payload, awesome! However, they are claiming improvements across the board. 3x the range, significantly faster, flies higher, uses less fuel. It doesn't pass a sniff test. Compare it to the Grob Strato 2c. Notice how long the wings are by comparison? This is a feature of nearly all subsonic high altitude aircraft. Also notice the how long the props are on the Grob, another feature of high altitude aircraft conspicuously missing on this aircraft. Pusher aircraft are not new. In fact they are as old as powered aviation itself. They generally aren't significantly more efficient. https://en.m.wikipedia.org/wiki/Grob_Strato_2C https://en.m.wikipedia.org/wiki/Grob_Strato_2C

asdfadsfgfdda 6y ago

The layout/payload may be similar to a TBM, but I'm guessing the wing loading and cruise altitude will be higher. So it's definitely feasible to go faster on less power.

VBprogrammer 6y ago
Aerodynamic drag is a square relation so the difference in drag there is about 40%. With 65% of the power. I think occam's razor applies here. Either the aerodynamics of reasonably modern aircraft designs leave a huge amount on the table or this startup is telling fibs. There are other reasons to be suspicious, modern diesel engines rely on a large amount of turbo charging to achieve sea level rated power, it's difficult to believe they are able to maintain this rated power to 50,000ft or 60,000ft. (In the case of the TBM the engine is actually capable of about 1300hp at sea level but is "flat rated" to what it can maintain at altitude). Finally, almost all high altitude aircraft have long wings (think the U2 as that is not far from what we are talking about here). Adding longer wings typically increases high altitude performance (there are aircraft with model variants where the wings got longer, like the twin commander). This aircraft appears to have borrowed a couple of surfboards.
- Tuna-Fish 6y ago
  > I think occam's razor applies here. Either the aerodynamics of reasonably modern aircraft designs leave a huge amount on the table or this startup is telling fibs. Aerodynamics of reasonably modern aircraft designs do leave a huge amount on the table. Generally for good reasons, though. The 500L is clearly almost entirely a laminar-flow design, unlike conventional aircraft (including the one you linked). Experience from gliders have shown that a small laminar flow design like this can have less than a third of the drag of what a conventionally shaped design of roughly similar size. There are two major downsides to designing like this: Firstly, the shape is entirely determined by physics, leaving very little wiggle room for manufacturing or practical concerns. Without modern composites, cost-effectively manufacturing the frame is impractical. Secondly, the great drag properties are very dependent on the properties of the skin of the aircraft. Laminar-flow gliders can have their glide ratios halved after accumulating a few too many insects on the leading edge. If you want to fly very high, (as this plane seems to want to), better hope you have an amazing de-icing system, or even a very small amount of ice will trash your aerodynamics.
  - VBprogrammer 6y ago
    Don't forget low speed handling and stall characteristics. There are so many places where the practically of this aircraft would fall down. Good luck fitting deicing boots to a wing which needs to be kept so clean polishing it makes a difference. Also, good luck trying to get an clearence to climb to 60,000ft around any busy international airspace. Regardless of any aerodynamics miracles this aircraft pulls off I'm sure we agree that it's climb performance will be distinctly average. That means it's going to take well over an hour to get up there. 20 mins or more could be spent in the RVSM band (FL280+) where most of the airliners are, expect to be vectored all over the sky while this happens. This is already a problem in something like the CJ2 which like to cruise higher than the airliners but aren't quite as fast. It's climb performance is considerably better than you would expect from this aircraft.

jillesvangurp 6y ago

If they reduce drag, which is exactly what they are claiming to have achieved, that would reduce the amount of horse power needed to overcome that drag. Less HP translates into better fuel economy. Basically this plane has the engine mounted on the back, which means center of gravity and wing position are quite a bit different. The nose cone looks very streamlined and crucially the wings are in front of the vortex produced by the prop. I'm guessing that that adds up to a bit of reduction in drag. The reason many planes have the engines mounted on the other side probably have to do with things like cooling, engine size, and other practical concerns.

VBprogrammer 6y ago
They are claiming improvements across almost all areas. If it flew as fast and as far as the competition on 50% less fuel, that would be amazing. If it flew 60 knots faster in the same fuel and payload, awesome! However, they are claiming improvements across the board. 3x the range, significantly faster, flies higher, uses less fuel. It doesn't pass a sniff test. Compare it to the Grob Strato 2c. Notice how long the wings are by comparison? This is a feature of nearly all subsonic high altitude aircraft. Also notice the how long the props are on the Grob, another feature of high altitude aircraft conspicuously missing on this aircraft. Pusher aircraft are not new. In fact they are as old as powered aviation itself. They generally aren't significantly more efficient. https://en.m.wikipedia.org/wiki/Grob_Strato_2C https://en.m.wikipedia.org/wiki/Grob_Strato_2C