5 ms·

I'm very skeptical of their claims of "unparalleled safety". Thanks to "autorotation"[1] regular helicopters can safely land in most situations even with comple

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. [1] https://en.wikipedia.org/wiki/Autorotation https://en.wikipedia.org/wiki/Autorotation

trevyn 9y ago
There’s also a parachute.
JasonFruit 9y ago
Could it be because autorotation requires a skillful, vigilant pilot, and the redundant systems of this machine help avoid urgent need for it?
- asterius 9y ago
  Autorotation is often taught after only 8 hours of training. It is very feasible to have an AFCS that will do an autorotation, but it is harder to find a place to land.
mrfusion 9y ago
Should be four or less considering each arm has two props. (Unless the motors aren’t powerful enough)
- zellyn 9y ago
  If all four on one side went out, I assume you'd be in big trouble.
  - CarVac 9y ago
    And if one on one side went out, you'd immediately descend.
  - FabHK 9y ago
    I'd imagine if two stacked ones go out, you'd be in trouble (as the centre of gravity will not be exactly in the intersection of the two diagonals).
    - SolarNet 9y ago
      Actually that's a benefit of the quad-copter design. It can sacrifice an axis of control in that situation (a "minor" one, like rotation about the gravity vector). In this case it would likely make the passengers sick, but it would still be able to fly in a controllable fashion. See this video: https://www.youtube.com/watch?v=ek0FrCaogcs https://www.youtube.com/watch?v=ek0FrCaogcs
      - anotheryou 9y ago
        with the counter-set props probably less spin even
        FabHK 9y ago
        Yes, you go from 8 df in the control to 7 df (instead of from 4 to 3). So, you could basically "hang" the weight off the remaining diagonal, and then use the working off-diagonal rotors to keep roll/yaw/pitch in line. But then the rotors on the diagonal have to generate twice the force. I'd rather not be a pax in this when two rotors fail.
- mannykannot 9y ago
  A lift/weight ratio of 2:1 would be quite remarkable, and the ceiling of a mere 4000' suggests that it does not have that sort of reserve, even at sea level and when being powered by the gasoline motor. Being anywhere somewhat hot or high would quickly erode that margin. On the other hand, the chances of four motors failing in the time it takes to set down is probably not high. Back to the first hand, if you do have multiple failures, it is not likely to be an optimal grouping.
neurotech1 9y ago
Small "personal" helicopters like the Robinson R22 are quite difficult to autorotate safely in a real emergency, due to low rotor inertia. [0] For the SureFly, Hypothetically if loss of several motors caused the aircraft to be unable to maintain altitude, the aircraft would not suddenly drop like a brick, but drift down to a controlled landing. [0] http://philip.greenspun.com/flying/robinson-r22 http://philip.greenspun.com/flying/robinson-r22
- pdelbarba 9y ago
  No, worse. That thing would turn into the tumble dryer from hell with partial power. It has no blade pitch control (like a helicopter does), requiring power on the motors in all four corners to maintain stability. The real emergency situation to worry about would be a total power failure. Failure of the individual electric motors will likely be extremely rare but a battery fire or controller failure could send this thing falling like a rock due to the lack of auto-rotation. It has a BRS chute but that won't do anything in the critical ~500ft band above ground level, too low to deploy normally. Additionally, I hope they've figured out how to guarantee safe chute deployment while inverted because of the tendency to tumble with no/partial power.
  - pc86 9y ago
    BRS parachutes have been tested as low as 260' AGL at 187 knots (several times faster than this craft would ever go) and individuals have reported successful deployments below 100' AGL[0] The question of course is how quickly it can be deployed in this craft as the vertical speed will likely be much faster than a Cessna or Cirrus in the event of total power failure. [0] https://www.flyingmag.com/g00/how-it-works-brs-aircraft-parachute https://www.flyingmag.com/g00/how-it-works-brs-aircraft-para...
    - pdelbarba 9y ago
      I can't imagine an inverted deployment at 100' would end well...
    - mannykannot 9y ago
downandout 9y ago
Yet even with autorotation, helicopters are somewhere between 27 and 85 times more dangerous than cars (depending on your methodology) [1]. [1] http://www.slate.com/articles/news_and_politics/explainer/2011/06/are_helicopters_safer_than_cars.html http://www.slate.com/articles/news_and_politics/explainer/20...
FabHK 9y ago
Electric motors are less complicated and more reliable than piston engines (as in small helicopters), I'd say (not sure about turbines). And then there's the ballistic parachute rescue system, though of course there's a minimum altitude you need for that. The Volocopter (a competing concept that actually exists and has had manned flights since 2016) has 18 rotors (six arms with 3 rotors each in a single plane), opposite rotors driven by the same battery/drivetrain ensemble, from what I gather, and remains controllable with up to 3 rotors (at least) faulty. I'd hope well engineered aircraft of this sort will surpass safety of traditional helicopters, but let's see.
nine_k 9y ago
They got a parachute, and with a rotor layout like this, attaching a parachute safely is pretty simple. Going down on a parachute is not exactly comfortable, but at least you're not going to crash at the earth like a falling rock. It turns a catastrophic crash into an unpleasant but likely quite safe collision.

trevyn 9y ago

There’s also a parachute.

JasonFruit 9y ago

Could it be because autorotation requires a skillful, vigilant pilot, and the redundant systems of this machine help avoid urgent need for it?

asterius 9y ago
Autorotation is often taught after only 8 hours of training. It is very feasible to have an AFCS that will do an autorotation, but it is harder to find a place to land.

mrfusion 9y ago

Should be four or less considering each arm has two props. (Unless the motors aren’t powerful enough)

zellyn 9y ago
If all four on one side went out, I assume you'd be in big trouble.
- CarVac 9y ago
  And if one on one side went out, you'd immediately descend.
- FabHK 9y ago
  I'd imagine if two stacked ones go out, you'd be in trouble (as the centre of gravity will not be exactly in the intersection of the two diagonals).
  - SolarNet 9y ago
    Actually that's a benefit of the quad-copter design. It can sacrifice an axis of control in that situation (a "minor" one, like rotation about the gravity vector). In this case it would likely make the passengers sick, but it would still be able to fly in a controllable fashion. See this video: https://www.youtube.com/watch?v=ek0FrCaogcs https://www.youtube.com/watch?v=ek0FrCaogcs
    - anotheryou 9y ago
      with the counter-set props probably less spin even
      - FabHK 9y ago
        Yes, you go from 8 df in the control to 7 df (instead of from 4 to 3). So, you could basically "hang" the weight off the remaining diagonal, and then use the working off-diagonal rotors to keep roll/yaw/pitch in line. But then the rotors on the diagonal have to generate twice the force. I'd rather not be a pax in this when two rotors fail.
mannykannot 9y ago
A lift/weight ratio of 2:1 would be quite remarkable, and the ceiling of a mere 4000' suggests that it does not have that sort of reserve, even at sea level and when being powered by the gasoline motor. Being anywhere somewhat hot or high would quickly erode that margin. On the other hand, the chances of four motors failing in the time it takes to set down is probably not high. Back to the first hand, if you do have multiple failures, it is not likely to be an optimal grouping.

neurotech1 9y ago

Small "personal" helicopters like the Robinson R22 are quite difficult to autorotate safely in a real emergency, due to low rotor inertia. [0] For the SureFly, Hypothetically if loss of several motors caused the aircraft to be unable to maintain altitude, the aircraft would not suddenly drop like a brick, but drift down to a controlled landing. [0] http://philip.greenspun.com/flying/robinson-r22 http://philip.greenspun.com/flying/robinson-r22

pdelbarba 9y ago
No, worse. That thing would turn into the tumble dryer from hell with partial power. It has no blade pitch control (like a helicopter does), requiring power on the motors in all four corners to maintain stability. The real emergency situation to worry about would be a total power failure. Failure of the individual electric motors will likely be extremely rare but a battery fire or controller failure could send this thing falling like a rock due to the lack of auto-rotation. It has a BRS chute but that won't do anything in the critical ~500ft band above ground level, too low to deploy normally. Additionally, I hope they've figured out how to guarantee safe chute deployment while inverted because of the tendency to tumble with no/partial power.
- pc86 9y ago
  BRS parachutes have been tested as low as 260' AGL at 187 knots (several times faster than this craft would ever go) and individuals have reported successful deployments below 100' AGL[0] The question of course is how quickly it can be deployed in this craft as the vertical speed will likely be much faster than a Cessna or Cirrus in the event of total power failure. [0] https://www.flyingmag.com/g00/how-it-works-brs-aircraft-parachute https://www.flyingmag.com/g00/how-it-works-brs-aircraft-para...
  - pdelbarba 9y ago
    I can't imagine an inverted deployment at 100' would end well...
  - mannykannot 9y ago

downandout 9y ago

Yet even with autorotation, helicopters are somewhere between 27 and 85 times more dangerous than cars (depending on your methodology) [1]. [1] http://www.slate.com/articles/news_and_politics/explainer/2011/06/are_helicopters_safer_than_cars.html http://www.slate.com/articles/news_and_politics/explainer/20...

FabHK 9y ago

Electric motors are less complicated and more reliable than piston engines (as in small helicopters), I'd say (not sure about turbines). And then there's the ballistic parachute rescue system, though of course there's a minimum altitude you need for that. The Volocopter (a competing concept that actually exists and has had manned flights since 2016) has 18 rotors (six arms with 3 rotors each in a single plane), opposite rotors driven by the same battery/drivetrain ensemble, from what I gather, and remains controllable with up to 3 rotors (at least) faulty. I'd hope well engineered aircraft of this sort will surpass safety of traditional helicopters, but let's see.

nine_k 9y ago

They got a parachute, and with a rotor layout like this, attaching a parachute safely is pretty simple. Going down on a parachute is not exactly comfortable, but at least you're not going to crash at the earth like a falling rock. It turns a catastrophic crash into an unpleasant but likely quite safe collision.