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Comment by Torkel | Hacker News Reader

This is true, but also not true. Helicopters are stuck as a concept: large main rotor and tailrotor and also expensive parts and traditional aerospace practices. There are other physical paths, e.g. Osprey, Cheyenne.

But the big thing now is batteries and electronics and brushless motors. It allows flight at a whole new level of cost/safety.

Compare with toy-drones - your point here to me reads like ”there’s nothing new with these quad-rotor drones, we’ve had gas rc helicopters since forever”. And that is similarly wrong as saying these new vtol concepts are just helicopters. Fundamental tech enables the concept of flight to be reinvented using first principles. We know a bit of where this is going in small quads. For manned flight it is still unknown.

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Helicopters are "stuck" because they've largely settled into an optimal configuration over the 70 years if experience designing helicopters. Some of the first helicopters had multiple rotors [1], but those were abandoned for good reasons They have a large main rotor because larger rotors provider greater efficiency. The single large rotor also provides the ability to perform autorotation in the event of power failure. Batteries are also bad choices for aircraft since they have very low energy density by unit of mass [2] combined with the fact they don't get lighter as energy is expended like thermochemical fuel.

These are the main reasons why quadro copters largely remain in the realm of drones and toys. These are the use cases where mechanical simplicity of four fixed pitch electric motors shine, and the shortcomings of reduced safety and lifting power aren't big issues (cameras weigh less than people and their families don't sue when they get smashed in a crash). You point out helicopters aerospace practices as a drawback, but in reality those practices emerged to deal with the responsibility and demands of human air transport. What is it going to cost to insure one if these flying cars? How many people's life insurance policies is going to cover rides in these things?

Definitely quadrocopters have made their mark in consumer electronics and even some commercial applications. But I am very dubious that people will be flying in electric multirotor craft.

1. https://en.m.wikipedia.org/wiki/Focke-Wulf_Fw_61

2. https://upload.wikimedia.org/wikipedia/commons/thumb/c/c6/En...

> The single large rotor also provides the ability to perform autorotation in the event of power failure.

That's a nice fantasy but when the SHTF nobody ever seems to be able to pull off an autorotation landing without fatalities. You need enough forward speed and control authority to make it work. An incident when you're at or near hover is unrecoverable.

An incident at or near hover is close to the ground, and so has much better chances of survival.

The issue with multiple rotors is that if one rotor fails the craft immediately pitches over and crashes. The Chinook solves this because the two rotors have a linked shaft. Definitely a quadrocopter becomes unstable with only 3/4 rotors. Maybe the octocopter posted elsewhere in this thread can sustain one failure and still land.

The japanese one has dual props in each position, so it can loose one propeller/motor and still fly (unless they are idiots).

The military might be willing to risk flying people in electric multirotor craft for a few specialized missions such as casualty evacuation.

The military and other rescue service have been evacuating casualties since the 1950s on helicopters. What advantage does this provide over a helicopter? These electric craft have tiny lifting capacity, only 1 or 2 people, as well as much shorter ranges.

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