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Comment by JudasGoat | Hacker News Reader

It would seem as though electric power could create a much safer helicopter. An electric motor powering the rotor with the engine acting as a generator much like a diesel locomotive. A smallish battery would give enough power to descend safely in case of engine failure.

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You can descend safely with engine failure; it’s called autorotation. Sounds like they probably did so, but the floats were not properly inflated. Also a harness catching a fuel shutoff switch; bad. So many small things that can go wrong, compounding to fatalities.

You can even see, in captured footage, that it descends fine, and then starts to turn to its side due to the floats not being properly inflated.

https://twitter.com/JJmagers/status/972974463175286784 for the video.

Helicopters already descend safely during power loss with autorotation, which every pilot trains. The landing site, failure of a float, and doors off operation were bigger problems here, as well as the passengers not knowing how to rapidly get out of their harness.

From the look of it, the pilot actually did alright, and successfully autorotated to a landing he expected to work. The aircraft had other ideas.

The landing went fine. The helicopter was even fully intact following the landing, which is often not the case for helicopter crash landings.

It's just that there was no good plan for what would happen after a water landing. The pilot, with his greater familiarity with the restraints, was able to improvise, but no one else could.

I would quite happily have myself bodily transported by a small fleet of drones, of the average Maxi- variety, appropriately tethered into a space suit, with perhaps one or two Over-drones there, just in case something happens with the swarm and I splash into the ocean .. on the other hand, maybe the Over-drones would be carrying supplies and setting up the BBQ on the base island, who knows .

Point I wanna make is, hell yeah there have to be better flying things on the horizon. Gimme my drone-fleet and proper space-suits, yo!

You can fly a bit without power by simply doing autorotation.

Autorotation in a helicopter is just falling less quickly. The speed at which you fall is highly dependent on the weight of the aircraft in flight.

Which sounds weird to me since objects normally fall at the same speed (9.8 m/s^2) and I would have assumed that more weight results in more potential energy which gives you more kinetic energy in the wings to stop the plane smoothly, but you also have to stop more mass. So I would have thought the weight cancels out of the equation, but wikipedia confirmed it depends on weight (not stating whether the effect was positive or negative on fall speed).

I don't get whats the effect of weight and why, could someone with helicopter/physics background explain?

"objects normally fall at the same speed (9.8 m/s^2)"

That's ignoring air resistance, which in the case of flying machines is substantial!

In vacuum!

g (9.8 m/s^2) is an acceleration, not a speed. It's right there in the units. The actual terminal velocity of an object is meet when its wind resistance -- which is a force (acceleration with mass) with negative magnitude -- matches g. Until then, it will accelerate.

So, generally, the larger the surface-area-to-mass ratio of an object, the lower its terminal velocity. Aerodynamics also plays a part, of course. So, a lead feather will have a much higher terminal velocity than a real feather, due to the extra mass that the wind resistance is fighting against. Meanwhile, g is an acceleration so it affects all mass equally.

Here's a really cool video of a feather and bowling ball falling in vacuum together:

https://youtu.be/frZ9dN_ATew

Since aircraft rely on lift, which is also a force, to overcome gravity, minimizing weight is ideal. Gravity will affect all the mass equally. But the same lift force with double the mass will only be half as effective.

The helicopter people on this forum seem to conclude that the fall speed of heavier helicopters is slower:

https://www.pprune.org/rotorheads/484972-weight-vs-rod-autor...

Ah, I see where you were going now. That is interesting; never heard of it before. I agree with you, that at first glance it seems like the gain in potential energy would be countered by the increase in the lift force necessary.

Maybe there's some sort of flat efficiency loss going on, that is overcome by the higher energies present in the heavier scenarios? It does seem that everyone is in agreement that the heavier helicoptor would require more applied pitch. Which may not actually be desirable, given my impression that a pilot would attempt to burn the kinetic energy in the rotors to lift via pitching the blades right before landing.

Let me correct myself: "[...] fall at the same speed because they have the same acceleration (9.8 m/s^2)"

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