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Comment by jacquesm | Hacker News Reader

> do you have any idea what part(s) are failing so quickly? The rotors, the motors, the battery?

It doesn't really matter what fails, what matters is that there is no way to do a controlled descent once anything goes wrong on a loaded drone because there is no margin for error. A drone this heavy relies on the whole chain of components functioning perfectly.

I'm surprised it is as good as it is given the number of parts. If it were a winged drone you'd at least have a chance to glide it to a safe spot, but a drone that is kept up by spinning props can only crash uncontrolled. There was a video of downing one in a more controlled way but the only fault it could cover was single rotor failure and even then the amount of control was very limited.

These things have absolutely no business over areas occupied by people.

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> what matters is that there is no way to do a controlled descent once anything goes wrong on a loaded drone because there is no margin for error.

Not entirely true. The drone had a parachute system to allow a controlled descent in situations like this and an alarm to alert nearby people to its descent. The problem here was that the parachute's single tether was severed shortly after deployment.

> The drone had a parachute system to allow a controlled descent

The parachute would allow the drone to avoid a rapid descent. Most parachute systems are not steerable/flyable so they won't make it a controlled descent.

Parachutes won't control the descent. Might slow it down a little, but that is of arguable value if all 10 kg landed on top of those kids mentioned in the article.

They don't control the descent, but they do control the descent. That is the descent (rate thereof) is controlled to a safe speed while the alarm alerts those below of its approach.

They have parachutes installed. In the 2nd crash it deployed but the line hit a sharp part of the craft and was severed. Upgrades are being made (redundant cords and metal braiding) and the whole fleet was grounded in the meantime.

  If it were a winged drone you'd at
  least have a chance to glide it to
  a safe spot, but a drone

The last time I looked at the retail quadcopter/RC plane market, when faced with a communications failure most of the quadcopters would return to the launch point and safely land. None of the RC planes had such a function - most seemed to just turn off the propeller and glide in whatever direction they were facing at the time.

Seemed to me the quadcopter response to communication failures was a much safer one. Is this still the case? It was quite some time ago.

>The last time I looked at the retail quadcopter/RC plane market, when faced with a communications failure most of the quadcopters would return to the launch point and safely land. None of the RC planes had such a function - most seemed to just turn off the propeller and glide in whatever direction they were facing at the time.

Once you have a quadcopter you've got enough digital hardware and software that adding "return to base" is basically free since it's just an additional software routeine.

RC planes don't already have the required hardware/software to implement a return to base feature because they don't need it and of course nobody is going to greatly increase the cost and complexity of the product just to add that one feature.

A handful of the quad controllers also support planes. I have multiple RC planes with that functionality - it adds a little complexity but not a ton.

> The last time I looked at the retail quadcopter/RC plane market, when faced with a communications failure most of the quadcopters would return to the launch point and safely land.

That isn't really accurate at all.

> https://hobbyking.com/en_us/turnigy-t1000fc-auto-pilot-syste...

>https://www.amazon.com/Parrot-Disco-FPV-minutes-goggles/dp/B...

Very few micro and mini quads have this functionality.

Return To Home functionality is common any medium and larger RC aircraft intended for FPV flying.

Often fixed wing RC with RTH functionality won't attempt to land, it return to home and enter a circular holding pattern until contact is re-established or the battery fails.

I tested some quadcopters and all had the behavior to land immediately on connection loss, no matter what is below them. Better not have something like that happening above a pond. So no automatic navigating to a starting point. It has been a few years, maybe that changed.

3D Robotics Solo has that feature (return to launch), but that was 5 years ago now. You could also set it so when the battery started to get too low it would return home as well. But that was one of the most advanced hobby drones in terms of software that existed at the time. DJI now uses it as well. It's all built into ardupilot. http://ardupilot.org/

Is there any reason a drone couldn't autorotate like a helicopter does to slow its descent?

For autorotation you need to passively stay upright and a certain propeller area to weight ratio.

All of which are not present in a typical multirotor.

And you need pitch control ("collective").

Helo autorotation largely requires the momentum of the blades to keep going after engine failure (as well as the pitch and forward momentum). I don't think the blades on small drones are heaby enough to store enough momentum for autorotation.

More importantly, most drones cannot physically adjust the tilt of the rotor blades (which is called collective pitch control in helicopters). Helicopter autorotation requires rotors with a lot of angular momentum and usually an abrupt change in the collective pitch right before landing to turn that momentum into thrust and slow the helicopter down.

There are RC aircraft with collective pitch controls, like most RC helicopters and even some multirotors. These RC aircraft generally can autorotate, as well as do things that are probably not practical for full-scale aircraft to do, like fly upside down. :)

A collective pitch quadcopter flying upside down: https://youtu.be/MVL_Hf4ilLg?t=162

An RC helicopter doing, well, all sorts of acrobatics that hardly make sense: https://youtu.be/KmPchrGW1TQ?t=48

An RC helicopter autorotating: https://youtu.be/bxQ5kwqiPN4?t=136 (this one has an internal combustion engine, although that shouldn't make much of a difference for autorotation)

>that hardly make sense

Just a guess: stronger strength to weight, and power to weight ratios, compared to the real thing. The tail rotor in particular appears to be quite a bit more powerful for the weight of the model than would be expected in a full size aircraft. And then also, these kinds of movements with a person inside? Haha! No!

Yeah, I've been pretty deep in the RC community, but what doesn't make sense to me is the physical skills of pilots like that! Handling orientation changes like that is insanely difficult. I practiced flying RC helis for a while in a simulator and even the basic orientation exercises are pretty challenging.

A helicopter's rotor has a complex control system that has you changing the pitch of the rotor blades and the angle of the rotor disk, with the rotor behaving similarly to the wing of an airplane. Quadcopters usually rely purely on thrust for control. For example to bank, the motors on one side spin faster (more thrust) and the motors on the other side spin slower (less thrust). If you lose a motor, or lose the ability to control a motor, you lose the ability to control the quad.

In comparison, a helicopter will have a clutch that can disengage the rotor from the engine and let it turn freely. The pilot still has the ability to control the rotor, so she has some control during the autorotation. At the end, just before landing/impact, she will perform a flare, using the rotational energy in the rotor to slow the helicopter's descent.

Why not autorotation? https://wikipedia.org/wiki/Autorotation

Is it less mass and therefore momentum in the rotor/drivechain?

That needs forward flight to work. A quad copter does not have a glide ratio high enough that it would be able to start up the rotors to spin fast enough to get some lift out of them. A quad copter is best modeled as a brick with a magic anti gravity device attached, if the anti gravity device fails it is a suspended brick and gravity will soon assert itself.

A real helicopter (or an auto-gyro) is best modeled as a rotating wing, as long as the blades rotate you can control the craft to greater or lesser extent. It still won't be pretty in a proper helicopter but at least you have a chance.

Additionally, you need "collective pitch" control, i.e. the ability to angle the rotor blades for windmilling and then for hover flight right before touchdown. Multicopters just have fixed-pitch rotors and rely on differential torque/thrust for attitude control and ascend.

>A quad copter is best modeled as a brick with a magic anti gravity device attached, if the anti gravity device fails it is a suspended brick and gravity will soon assert itself.

Very nice definition.

There isn't AFAIK such a neat distincion in English, in Italian the iron (the device you use for ironing, maybe flatiron?) has a specific name "ferro da stiro" so it is common to use it as a term of comparison for such a behaviour.

Is it possible to design a self-destruct sequence so powerful that the entire thing is fragmented to dust over a wide area?

I'm sorry, did you just suggest we pack explosives in commercial cargo drones as a safety measure? Explosives enough to vaporise 10kg drone plus its cargo. Are we looking at mini nukes here?

I don't know, as you can tell I don't know much about explosives. But you wouldn't need to literally vaporise it, I guess, and I doubt it'd need a miniature nuke.

In my defence, a quick search shows this story:

https://www.digitaltrends.com/cool-tech/amazon-delivery-dron...

So apparently it's not a stupid suggestion and Amazon are thinking along the same lines.

I only ask because it seems making drones land safely is hard. I mean, a paracute with a whistle is a great idea until it drifts in front of a car moving at high speed, or lands on a deaf person or shorts out a high-voltage cable. They all have problems. If there was a way to convert the failed drone into widely dispersed very small objects, the harm may be much lower.

Sure, but it might explode near people

I didn't say it had to be explosive, but at any rate, you know anyone can buy fireworks right?

I think the combination of being airborne, remotely controlled and high explosives might get you attention of a kind you would like to avoid.

maybe you could have started a new comment thread since your post doesn't remotely answer the question you quoted

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