There are also aerodynamic realities. There are limits on the performance of quadcopters. To get heavylift performance, say over 10000lbs, a quad will need to be huge, requiring lots of heavy arms. A single big rotor, with variable pitch, is much easier and more efficient at such scales.

I havent seen a quad that can autorotate, a necessary emergency trick if you want to carry people. When the power fails on a quad it just falls. Traditional helos can actually glide to a controlled landing.

the lack of ability to fly with one engine out, in a quad, is why most of the human-carrying systems proposed such as the eHang unit are what's known as an X8 configuration. Four arms, eight motors in a coaxial configuration on each arm. Can fly and land with a dead motor.

This one can fly with just one rotor running:

https://youtu.be/gfkRCzgHGq8

Admittedly it would be a pretty terrifying ride to the ground, but preferable to plummeting. There’s a lot of rotational energy in the aircraft though.

I think there’s probably significant scope for improvement in redundancy of these systems.

But can they fly with all the motors dead? What if they loose the supply of power from the battery system? A standard config can deal with that senario.

I am not aware of any multicopter design that can autorotate. Something like this with a tilt wing approach probably has some ability to glide:

https://youtu.be/gJrKmMM7vW0

They could. They just need variable pitch (aka collective) on all the blades. And this needs to be actuated by a different power system so that it remains operational when the main power stops. Helicopters use hydraulics, or even manual power.

Autorotation is where helicopters get their speed/altitude restrictions when carrying passengers. They generally are not allowed to hover at low altitude because from there they cannot safely autorotate onto the ground. If drones want to carry people, or carry heavy things over people, then they will need to develop some sort of plan. Total engine failure should never result in the total loss of the aircraft.

Over a sufficiently long and thorough testing period, I think x8 design multirotors with eight or more motors/props will prove to have a statistical rate of motor failure much lower than the incidence of single engine failure in small to mid size internal combustion engine and turbine helicopters.

It would have to monumentally better before I'd get into one that didn't have a backup plan. The motors could be 100% reliable, but the possibility of loosing power due to maintenance or control issues remains. A perfectly good motor is useless if the cable feeding it electricity shorts out.

> I'd imagine the reason a DJI drone's capabilities are so much greater than those of a helicopter carrying passengers is that the former can fall out of the sky every now and then and it's no big deal. The latter has to pass a whole lot of rigorous FAA (or equivalent) testing.

This reminded me of another comment I read recently, and I was actually able to remember where I read it! https://news.ycombinator.com/item?id=17723107

> Hi- I used to work in regulated pharma and I want to be clear: " The core problem is that the FDA-approved devices are optimized not for getting the best result, but for ensuring the manufacturer can't be blamed if something goes wrong" is a misleading statement. The reason everything is regulated is that sometimes things do go wrong, and it's necessary to have root cause attribution so the problem can be remedied and a fix deployed, and, if somebody did something illegal or dumb, they can be sanctioned.

(The quoted part of this comment, itself from a previous comment, is the part I found relevant, but I quoted the whole thing (reply and all) because I found the whole thing interesting.)

I think I can naively say with confidence that aviation and medical certification are very similarly rigorous.

So, it sounds to me that the autohover functionality you describe was perhaps the equivalent of Tesla "Autopilot" (which really amounts to auto-steer). The context of doing rescue lifesaving over sea is indeed very stringent, but at the same time, it's not going to be the end of the world if the helicopter moves around a bit, because it's in the open air. And if the situation is dire - strong crosswinds, or someone in critical condition - the pilot's training probably instructs them not to use it.

In this situation, letting the controls go for 2-3 seconds (as per the other comments here) is going to mean an unrecoverable crash, and perhaps a rotor blade might cut one of the cables and then you have 220kV waving everywhere, hitting other power lines, touching the ground..... no. You just find the best pilots that can hover Really Well™, and pay them metric stupid amounts of money so they don't go anywhere else.

Now I'm wondering if the pilots hold hovering competitions, in the same way people in the military frequently do target practice.

> Now I'm wondering if the pilots hold hovering competitions, in the same way people in the military frequently do target practice.

Yes. Have a read of "Rescue Pilot" by Jerry Grayson. It's a great read. He describes how they used to practise hovering with a single front wheel resting on the top of a particular coastal rock formation. It was a competition in the sense that one crew upped the ante by managing to balance their tail wheel on the rock, so the rest of the crews followed.

[1] https://www.bloomsbury.com/au/rescue-pilot-9781472918840/

Edit: Another link: http://rescuepilot.net/

They also open beer bottles with the skids to demonstrate precision control: https://www.youtube.com/results?search_query=helicopter+beer...

Similarly, some fire departments will do dexterity exercises like playing Jenga with rescue tools ("jaws of life" - https://www.jawsoflife.com/), and similar with ladder trucks and building blocks.

Wow, I just read the first chapter via https://issuu.com/bloomsburypublishing/docs/rescue_pilot.

Yet another book to add to the wishlist... I'm gonna need a job that gives me a bit of spare time, the pile is getting pretty big, haha.

The Vulcan bit leapt out at me; I've also read Vulcan 607! That book was purely technical; I would have appreciated an explanation about the political upheaval going on with the RAF at the time as well, I had absolutely no idea.

I had no idea hovering over sea is as complex as it is - of course everything underneath the helicopter is going up and down. So the helicopter needs to match that if it doesn't want to whomp onto the deck as it lands. Hah.

And so, in the same vein, hovering over a ship doing rescue operations is clearly going to preclude the use of the kind of autopilot described in the GGP comment.

I've been interested in the idea of flying since I was about 15, but I've been dragging my feet on getting involved for years (I'm 27 now) - if I love it, I'll be depressed I can't afford to dive right in, but if I hate it or can't get my head around the flight controls (I have poor hand-eye coordination, a lot of visual things don't "click" for me, and I can't keep an RC helicopter in the air), I'm not sure if I'd handle the let-down. Because of the expense involved I'm a bit on the fence about it.

Various health issues are why I didn't go the RAAF route a long time ago. (I'm not even sure what to name my condition - I've briefly described it at https://news.ycombinator.com/item?id=15005811 and https://news.ycombinator.com/item?id=17780498.)

I wonder why they don't instead suspend the line worker something like 50 feet below the helicopter to give themselves more margin for error. I guess the current method must be reliable enough that they don't bother.

Then you’d have two problems. There’s more wind up there than on the ground. The lineman would get blown around. Imagine a yo-yo tied to a drone hovering above the top of a tall tree. Now try to hold the yo-yo perfectly on a leaf.

That would mean a rope or similar, so the helicopter can actually take off.. that's not going to be stable!

At the end of the day, any mistake at 5 foot or 50 foot away is likely to be fatal!

Maybe to give the pilot a better view?