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There seem to be lots of plans (and even some working prototypes) for various autonomous flying cars and flying taxis.

Most of these seem to be based on vertical take-off using some variety of an electric quad-copter (or something very similar).

Conventional planes can glide in the event of engine failure, and traditional single rotor helicopters can auto-rotate. Both techniques should get the aircraft safely (more or less) down assuming the controls remain effective.

What is supposed to happen with a quad-copter based flying car/taxi if the power fails? I don't think the fixed props on a quad copter can auto-rotate, so how are they supposed to land? Ballistic parachutes? or something I've missed?

UPDATE for clarity (I hope). The media seem to use phrases like flying cars/flying taxis and autonomous aircraft or drones almost interchangeably. I'm talking about aircraft that have no (or minimal) wings (and therefore can't glide) and no capacity for auto-rotation. Here are a few examples...

enter image description here

enter image description here

enter image description here

Now have a look at this final photo, it shows an electric aircraft (a glider) with a battery fire. Being a glider the survival options were relatively simple, the pilot landed ASAP and got out of the aircraft. This doesn't seem to be an option for any of the designs I've pictured above. enter image description here

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    $\begingroup$ Does "economic" count as a failure mode for flying car projects as a whole? $\endgroup$
    – AEhere supports Monica
    Jan 7, 2019 at 14:09
  • $\begingroup$ Are you asking what the failure modes are, or about how to fail-safe in the case of power loss? $\endgroup$
    – bogl
    Jan 7, 2019 at 14:51
  • $\begingroup$ Failure modes are specific to a particular design. "Flying cars" are (at best) a vaguely defined concept, and each individual design will have its unique failure modes... no wings = no glide option; tiny rotors = no autorotate option; low altitude flight = ineffective ballistic parachute, and etc. $\endgroup$
    – Ralph J ♦
    Jan 7, 2019 at 15:10
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    $\begingroup$ Flying cars as vehicles generally suck because they make crappy aircraft and crappy cars at the same time, almost always combining the worst of the two not the best. $\endgroup$
    – John K
    Jan 7, 2019 at 17:11
  • $\begingroup$ @JohnK Your comment seems to be channeling the original F-111 or the JSF/F-35. evil grin $\endgroup$
    – KorvinStarmast
    Jan 7, 2019 at 20:36

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As I am closely working on some of these projects, I think I can answer.

Let me start from:

if the power fails

this is a rather extreme situation, since everyone is including emergency functionality in case the batteries get below a charge guard level, triggering an emergency landing (still powered).

So to have the "power fails" scenario that your phrasing suggests, you would need a sudden fire or failure of all the battery packs installed on the craft.

What's more likely is that one of the engines will fail, but that's less critical, since all these crafts will have 8 engines as a minimum exactly for this scenario. And once again, this will trigger a powered emergency landing.

Nevertheless, you are right in assuming that these crafts can't autorotate, and some projects are evaluating/have evaluated the inclusion of emergency parachutes similar to the ones seen on some general aviation fixed wing aircraft.

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  • $\begingroup$ So you are saying a power failure = crash. $\endgroup$
    – GdD
    Jan 7, 2019 at 14:31
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    $\begingroup$ @GdD "Emergency landing" != "crash" -- any more than dead sticking a Piper Cub is a "crash". The landing referred to here is powered and in control (which is the main reason for doubling up the motors). $\endgroup$
    – Zeiss Ikon
    Jan 7, 2019 at 14:33
  • $\begingroup$ @ZeissIkon I think that GdD is referring to the case suggested in the question, that I describe as unlikely, where all batteries fail at the same time, making all engines shutoff. $\endgroup$
    – Federico
    Jan 7, 2019 at 14:36
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    $\begingroup$ It's a very different scenario @ZeissIkon. A piper cub with total power loss is still controllable, you put it in a field and it isn't a crash, just an incident. An octocopter doesn't typically have control surfaces or a wing, so a power loss (assuming complete loss of electrical power) means loss of all lift and control. It may be unlikely, but it's going to happen at some point. $\endgroup$
    – GdD
    Jan 7, 2019 at 14:37
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    $\begingroup$ It's unlikely that you'll ever be able to build a machine so utterly reliable that failure is impossible, especially while keeping it affordable. In any case the question is what would happen if a power failure did happen, not how it's being made unlikely, and the answer is: "crunch". It's a fair answer, I was simply distilling it down. $\endgroup$
    – GdD
    Jan 7, 2019 at 14:45
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Note: This answer was for a previous version of the question

What you are asking about seems to be quad-copters, hex-copters, oct-copters. Flying cars are cars with wings designed for flying and will use airports for takeoff/landing (and gliding down in case of power loss) and driving on roads. See Terrafugia for example.

https://terrafugia.com/
enter image description here

Or this one, with VTOL capability; engine pods rotate forward for aircraft flying mode. enter image description here

Yes, pilots license is required. No, the average driver can't afford one - expect something like $250K price tag.

If the flying car loses power, it becomes a poor glider with unknown characteristics at this time.

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