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Comment by Roboprog | Hacker News Reader

Have you ever flown a (toy) helicopter? They are very non-intuitive. The torque of the main rotor causes every course change to have side effects that have to be compensated for.

Change the engine speed (lift), and the tail rotor needs to be adjusted so the copter does not yaw.

Change the tilt of the rotor blades to lean fore/after or drift to the side, and the engine needs to be sped up just a little to avoid slight loss of lift, and the tail rotor needs an ajustment to avoid yaw for the increased torque.

With multiple lifting, fixed, rotors, the electronics adjust the motor speeds for you to DWIM when you manipulate the sticks.

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My friend with a helicopter license felt cheated the first time he flew a plane and discovered how easy it was.

I once took a helicopter lesson, and I watched some videos about flying before hand.

One of the guys said: "A plane wants to fly. A helicopter wants to crash". This seems true to me: flying a helicopter is a continual act of not crashing.

It makes complete sense to me that a quadcopter is 100x easier to write software to autonomously fly vs a helicopter design.

There's a popular quote in the pilot community:

"The thing is, helicopters are different from planes. An airplane by it's nature wants to fly, and if not interfered with too strongly by unusual events or by a deliberately incompetent pilot, it will fly. A helicopter does not want to fly. It is maintained in the air by a variety of forces and controls working in opposition to each other, and if there is any disturbance in this delicate balance the helicopter stops flying; immediately and disastrously. There is no such thing as a gliding helicopter.

This is why being a helicopter pilot is so different from being an airplane pilot, and why in generality, airplane pilots are open, clear-eyed, buoyant extroverts and helicopter pilots are brooding introspective anticipators of trouble. They know if something bad has not happened it is about to."

Harry Reasoner, Approach magazine, November 1973

The pedant in me feels obligated to point out that helicopters can accomplish unpowered landings using autorotation.

If I had to make a choice about which unpowered craft to be in though-- I'll take the plane!

Autorotation requires action from a skilled pilot, it doesn't happen automatically. It's also one-shot maneuver - if you fail it, you're done, and you can't abort it like you could abort an unpowered plane landing.

How do you abort an unpowered plane landing?

You basically answered it yourself upthread - the plane has lots of forward velocity on approach, which gives the pilot a pretty big window to abort by gliding away, turning some of this forward velocity into lift.

Is there any data on this? Let's assume both an airplane and helicopter with highly trained and skilled pilots, with both aircraft high enough and going fast that there is time for the pilots to have time to fully prepare and react when they suddenly lose power.

It is certainly not obvious to a non-pilot like me that the plane is safer. If the plane can reach an airport, then sure. The plane pilot has less work to fly the plane then the auto rotating helicopter pilot has, so presumably can better concentrate on the landing. As long as he puts it down with enough room to stop, he should be fine.

But if they are not in range of an airport, so it is going to be a landing in a park or on a highway or something like that, would the plane still be safer? From the various videos I've seen of landings under such conditions, it seems that the big killer for planes is that they land with a lot of forward velocity. Essentially an unpowered plane landing outside an airport becomes a rough touchdown followed by effectively a high speed car crash in a car that was not really designed for that kind of crash.

The helicopter, on the other hand, wouldn't have much horizontal velocity, and so it would just be a rough landing.

I fly RC planes, or on a good day, gliders. Much more relaxing.

If I can get an indoor toy heli to hop from one kitchen counter to the other, I feel like I've accomplished something. They are slippery beasts. I don't even want to think about flying a heli outside in wind.

We watched a real heli rescue some hikers/climbers in the park outside Las Vegas on a windy day a few years ago on vacation. The wind was blowing against the cliff. Dicey stuff.

Robert Mason's book on being a Huey pilot in Vietnam, 'Chickenhawk'does a great job of explaining traditional helo dynamics. Great book.

http://en.wikipedia.org/wiki/Chickenhawk_%28book%29

Also, with a multicopter you have N identical motors. Turning, moving and tilting is still complicated, but easier enough for the electronics of today

But why there's no trend of multicopters replacing helicopters? Big ones, with humans inside.

Multiple small rotors is much less efficient than one big rotor, especially at bigger scale. So it's not economical.

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