I'm very skeptical of their claims of "unparalleled safety". Thanks to "autorotation"[1] regular helicopters can safely land in most situations even with complete power failure. The claims of safety of this craft seems to derive from N+1 battery redundancy which isn't that impressive. They say they have 8 independent motors, but don't say how many are needed to stay aloft.
SureFly – a personal helicopter designed for safe and easy flight
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Re: SureFly – a personal helicopter designed for safe and easy flight
#12Wait: - Curb Weight: 1100lbs - Max Takeoff Weight: 1500lbs So... you, your passenger, and any cargo combined can't weigh more than 400 pounds? That's a pretty serious limit for people hoping to transport multiple adults. And "precision agriculture" or the sorts of practical uses they discuss all go right out the window.
The BMI chart maxes out healthy weights at 192. So unless you have two NBA players or something, it should work well for most but perhaps not all healthy people.
Average weights (no median, sorry) from the CDC (https://www.cdc.gov/nchs/fastats/body-measurements.htm):
>Men: 195.7 pounds
>Women: 168.5 pounds
So this could carry an average man, average woman, and under 36 pounds. At that point, the weight of your clothing or a bottle of wine becomes very important.
Re: SureFly – a personal helicopter designed for safe and easy flight
#13I'm very skeptical of their claims of "unparalleled safety". Thanks to "autorotation"[1] regular helicopters can safely land in most situations even with complete power failure. The claims of safety of this craft seems to derive from N+1 battery redundancy which isn't that impressive. They say they have 8 independent motors, but don't say how many are needed to stay aloft. [1] https://en.wikipedia.org/wiki/Autorotati…
There’s also a parachute.
Re: SureFly – a personal helicopter designed for safe and easy flight
#14Video "tour" here (still doesn't show it flying): https://www.youtube.com/watch?v=elhiaxMiRuY&t=19s
Also, the inaugural flight at CES was scrapped due to a "light sprinkling" of rain: http://www.bbc.com/news/technology-42616034
Re: SureFly – a personal helicopter designed for safe and easy flight
#15I thought gasoline turbine generators are sort of here (used in hybrid buses), womder why they stuck with piston generator. Also, any ideas what battery pack you’d need to do the same 70miles?
My best guess is fuel efficiency at small size scales and is probably the same reason that make them economical in large buses, but not small cars. The usual intuition is explained using the Reynolds number, a dimensionless quantity that can help to predict the possibility of maintaining laminar flow or wether the flow breaks down into turbulence in the generator, drastically reducing efficiency in the compression-combustion-expansion cycle. As a side note, when I did a type rating on the Eurocopter AS350, I learned that the gas turbine could also run on normal automobile gasoline instead of Jet-A 1 for a limited amount of time in emergencies with drastically reduced limits on altitude, torque etc...
Re: SureFly – a personal helicopter designed for safe and easy flight
#16What is the benefit of more, smaller rotor blades over fewer, larger ones? I thought that the area of air that the blades worked on scaled with pi-r-squared, which favours fewer larger rotor blades, as seen on most helicopters?
I can't think of any benefits of this layout other than reducing the size of the landing field you'll need. And I guess less complexity on the part of the rotors, no tail rotor with associated dangers etc. I can think of some significant downsides though. 1. This is fixed pitch, not collective pitch. That means any change in the attitude of the aircraft requires one or more sets of rotors to change their speed of rot…
Expanding on your point #1: The inertia of large props means they can't change speed quickly, so there will be lag in the control inputs. (In toy quadcopters, electric motor torque is so high vs prop inertia that lag is a non-issue.) Collective pitch controls don't exhibit this lag. Electronic controls can compensate for inertia lag to some extent, but they have to be carefully designed using control theory, and if they fail the copter will likely be uncontrollable.
Re: SureFly – a personal helicopter designed for safe and easy flight
#17Wait: - Curb Weight: 1100lbs - Max Takeoff Weight: 1500lbs So... you, your passenger, and any cargo combined can't weigh more than 400 pounds? That's a pretty serious limit for people hoping to transport multiple adults. And "precision agriculture" or the sorts of practical uses they discuss all go right out the window.
You should look at the usable payload of a Cessna 150 or Piper Cub, and keep in mind that figure includes fuel, if you think that's low. Weight and balance is something you have to pay close attention to in aviation in general, and what your passengers are carrying does matter.
Re: SureFly – a personal helicopter designed for safe and easy flight
#18Neat!
Although I think it only goes about half the speed, half the flight ceiling and a third the range of an average helicopter. Maybe if these guys get some market traction a ton of other entrants will come and the dream of personal flight will finally “take off”.
I wonder what maintenance requirements will be like.
Re: SureFly – a personal helicopter designed for safe and easy flight
#19A part of me thinks this is really cool tech and it would be amazing for anyone to be able to just hop aboard their personal helicopter and fly wherever they want, but then another part of me thinks of the future this would create, skies no longer clear, filled with objects buzzing around and what hell that would be, on top of the already stressful and crazy life we have now.
It's the kind of situation where I think I'd actually rather the tech never exist.
Re: SureFly – a personal helicopter designed for safe and easy flight
#20A part of me thinks this is really cool tech and it would be amazing for anyone to be able to just hop aboard their personal helicopter and fly wherever they want, but then another part of me thinks of the future this would create, skies no longer clear, filled with objects buzzing around and what hell that would be, on top of the already stressful and crazy life we have now. It's the kind of situation where I think…
I empathize but I think that attitude is an artifact of the age we grew up in. I'm sure equestrians felt the same way when those rackety automobile contraptions started zooming around.