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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,

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
    For a drogue-deployed parachute, horizontal speed helps, as the required travel through the air is accomplished faster, and therefore with less drop. BRS parachutes use a rocket to fully extend the lines, but there is still the matter of inflating the canopy.
FabHK 9y ago
> 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. Source? I'd think loss of two stacked rotors would lead to loss of control, tumble, and dropping like a brick (until BRS deployed), not controlled descent and landing.
- gr3yh47 9y ago
  there's a parachute
  - FabHK 9y ago
    that's what I mean by BRS deployment. https://en.wikipedia.org/wiki/Ballistic_Recovery_Systems https://en.wikipedia.org/wiki/Ballistic_Recovery_Systems
    - gr3yh47 9y ago
      my mistake. thanks for the link
659087 9y ago
Robinsons in general have this problem (among others, such as their tendency to disassemble their own rotor systems in flight, and their incredibly awkward t-bar cyclic controls), but I'd still rather take my chances with a Robinson autorotation than rely on a ballistic parachute system. That said, I would never willingly fly this thing or a Robinson, so I guess I'll never have to deal with either situation.

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
  For a drogue-deployed parachute, horizontal speed helps, as the required travel through the air is accomplished faster, and therefore with less drop. BRS parachutes use a rocket to fully extend the lines, but there is still the matter of inflating the canopy.

FabHK 9y ago

> 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. Source? I'd think loss of two stacked rotors would lead to loss of control, tumble, and dropping like a brick (until BRS deployed), not controlled descent and landing.

gr3yh47 9y ago
there's a parachute
- FabHK 9y ago
  that's what I mean by BRS deployment. https://en.wikipedia.org/wiki/Ballistic_Recovery_Systems https://en.wikipedia.org/wiki/Ballistic_Recovery_Systems
  - gr3yh47 9y ago
    my mistake. thanks for the link

659087 9y ago

Robinsons in general have this problem (among others, such as their tendency to disassemble their own rotor systems in flight, and their incredibly awkward t-bar cyclic controls), but I'd still rather take my chances with a Robinson autorotation than rely on a ballistic parachute system. That said, I would never willingly fly this thing or a Robinson, so I guess I'll never have to deal with either situation.