Having worked in other hardware startups though, I'm guessing what actually happened was a few years of reinventing the wheel and learning on the job. Safe systems don't look any different to non safe systems to an outsider, so unless there's a real buy in from management it's very hard to build them.
In what way do multirotors / drones differ?
Average multicopter designs would seem to be incapable of autorotation for aerodynamic and technical reasons. The technical reason being that the BLDC motors used are typically permanent magnet synchronous machines, which develop significant holding torque in most (driver) failure modes and there is no clutch to disconnect the motor from the propeller.
*There are some exceptions: https://www.droneguru.net/collective-pitch-drones/
A multirotor on the other had doesn't have the ability to glide, like a fixed wing or a helicopter. Any safety will have to be engineered in by making sure that a single rotor failure (or even multiple) can be coped with correctly and reliably.
Some helicopters with very heavy blades with lots of angular momentum have been built, but it makes the blades heavy which requires a more powerful engine which makes the whole craft heavier which means you need even more angular momentum...you get the idea. It's an engineering nightmare so it's atypical.
Can anyone with more knowledge chime in?
I’m off to bed, otherwise I’d try looking in to it.
Multirotors I believe require active control of every individual rotor instead of straightforward big angular momentum. Which I believe is part of why they are seen on drones.
Most motors on multirotors are BLDC motors that require active control to make them spin. Voltage gets applied to the motor phases sequentially to make it spin. However, when they're completely open-circuit, they actually spin quite freely! I've seen the ones I had (26" prop) windmill quite well in a mild breeze. The trick, though is that you're probably not going to get much descent-arrest out of open-circuit BLDCs. Another possibility is short-circuited BLDCs; in that condition, the rotos are quite tough to turn. My speculation is that the props wouldn't spin much at all in a short-circuit condition. Buuuuut... if ESCs were able to modulate the open/short-circuit condition (even without power to actively spin the motors), I suspect you might be able to get some kind of arrested descent situation.
I've been thinking of building an ESC from scratch this winter... this might be a useful feature to experiement with!
The FAA generally requires certified helicopters to have a 30 minute fuel reserve in order to allow a safe diversion to an alternate landing site. With lithium battery power, once you subtract out the reserve time there's hardly any range left. (It might be possible to obtain some exemptions to the reserve regulations in limited circumstances.)
Experimentals don’t get to waive fuel reserve requirements (which are Part 91 flight requirements [pilot responsibility to comply], not Part 23/25 type design requirements [designer responsibility]).
(Even if the range and safety issues can be resolved it's not clear that the target market even exists, but that's a separate problem.)
The absolute bottom line offering of any small aircraft has to be that its safe (or at least, the failure rate is acceptable - which means at least comparable to modern helicopters). That's the innovation that anyone entering the market needs to bring.
Making a new type of aircraft that is significantly more dangerous and requires significantly less training (so it is unrealistic to expect the consumer to understand the risk) is just valuing profits over human lives - full stop.
Are you still okay with unsafe flying machines when they start falling out of the sky and killing people on the ground? As mentioned previously, these aren't even supposed to require a pilot's license, so you can't expect the customer to be trained like a pilot.
The FAA rules are written in blood. If people want to experiment with new types of aircraft responsibly, that's fine! There is even a specific process for that, it's called an experimental certification.
But selling these things to untrained consumers is just completely, utterly, reprehensibly irresponsible. That's probably why Kitty Hawk returned deposits - they realized the machines just weren't safe enough to sell to people.
Safe + not working eventually leads to bankruptcy too, but people don't die in that case.
Not to say that advancing aerospace engineering should be totally without risk. But these folks are not building space vehicle or fighter planes, they're building commercial aircraft. In that sector, tolerance for risk is far lower, as it should be.
I'm sure they've started from zero several times with entirely new designs. There's no point worrying overly much about safety if you only plan to fly something once.
Sounds like a problem with management, which isn't surprising. Sebastian Thrun is a brilliant researcher, but he has yet to turn any of his ideas into sustainable technologies or companies. Self-driving cars aren't real yet, and Udacity is going through some rough times. To the best of my knowledge Udacity has never been profitable (please correct me if I am wrong).
Maybe he'll turn around Udacity (I doubt it, although I really hope so). My point is this man chases after shiny things, and then leaves as soon as there's another shiny thing for him to pursue. He does the fun stuff with early development, and then loses interest when you get to the hard slog of making everything sustainable.
Similar to self-driving cars, he was able to get his flying machines working well enough for some really awesome demos - but he can't commercialize the technology because it's still demoware.
I want to compare this to Icarus because superficially it's so appealing, but in the end Sebastian is going to be incredibly wealthy and never having really lost anything. He will even likely continue to be heralded as a genius by many (and sometimes rightfully so).
We are led to believe that safety is the most important aspect of any part of our work. At least that’s what we’re told at group meetings and company-wide meetings. But when push comes to shove and the (arbitrary) schedule demand a test, hacky code is produced, checks fall off the list, and errors do happen.
Progress seems to be more important than safety. We are instructed to show some sort of significant return on investment within 6-12 months for the funding we’ve received. It’s pretty sad.
Telling mangers that we need to take it low and slow at first makes them angry and ignore the engineers who do the good work in exchange for engineers who do it fast.
Also, you probably think you're anonymous and safe in setting this comment out here but you and your employer are trivially identifiable from this comment and a couple of others made on HN so you may want to petition the mods to kill this comment on the off chance that your employer gets wind of this, it might be a career limiting thing.
Some days I love hacker news.
I'm trying to think of reasons it would be good to have low rotors... maybe something about noise experienced by the passengers?
That’s a common fallacy, early rockets placed the nozzle’s on top based on this assumption but it’s not useful. Ex: https://en.m.wikipedia.org/wiki/Rocket#/media/File%3AGoddard... The issue is the thrust is in line with the angle of the craft so you get the same thrust vector from below or above the aircraft.
Take a modern twin engine aircraft and they can turn by changing the thrust from each engine, but when the engines are outputting identical thrust they don’t add stability. In both cases rotating the aircraft also rotates the net thrust in an identical fashion. Which means there is zero restoring force from the engines to return them to the original orientation.
PS: Fixed wing aircraft get stability from their airframes not their engines. https://en.m.wikipedia.org/wiki/Longitudinal_static_stabilit... Though in fighter jets this may be aided by active control.
At any rate, the Volocopter  has the rotors on top, and while it might not look as sporty as the Kitty Hawk, I don't find it annoyingly goofy.
Well that isn’t exactly difficult to achieve if no one was on it. I’d like to know the data if it was carrying a crash dummy.
Early on in a project you need vision and innovation, "fake it 'till you make it".
Get a demo working, even if it only works 20% of the time or covers one use case poorly.
But at some point, along comes actual reality.
The most defensible practice are at least inherently modular and could be stitched together - really the deception would be highly unnecessary
What. How is it appropriate fo HR to be involved in reports of safety issues. This reads like there was confidential channel to self selection layoffs.
And, in particular, it doesn't have the people-decapitating and knee-cap-smashing rotors below the passenger capsule, but above (like a conventional helicopter).
What if there is bird strike or the blades somehow dismantle from the fan and fly towards the pilot.
Also this being made for non professional pilots/passengers what if a passenger tries to board/de-board while the fans are still spinning?
At this point, I assume the aircraft keeps morphing into whatever the next iteration of managers/designers deem highest priority to keep the company afloat