Have Multi Rotors Killed the Helicopter?

I think not and am expecting a resurgence of the good old heli.

This article puts forward a lot of good arguments for the helicopter (all be it in baby terms) but do you think there is truth in these claims?

A new Chinese unmanned helicopter might be the industry’s first critical step to a functional aerial logistic platform in the near future. This unmanned helicopter, produced by Ziyan UAVexcelled its counterparts by its outstanding performance in load-bearing, safety and speed...

Full story here.

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Comment by Rana on July 16, 2016 at 12:27am

Absolutely not, tanks & helis would be there for ever ! 

Comment by Gary McCray on July 16, 2016 at 12:43pm

Unmanned helicopters will in the end have a very significant role in a lot of UAV uses.

The large diameter rotor is intrisically more efficient than the multiple propellers of similar capability multirotors and there fore have higher carrying capacity and range.

They can also more easily incorporate fuel engines for greatly increased range.

Although the continuously variable pitch rotor hub is seriously complicated, at this point, 3D helicopter competition has produced extremely rugged and reliable hubs, certainly on a par with any multi rotors reliability.

The statement in the article about the US Military abandoning multirotors back in the 1960's is however completely irrelevant.

That was a manned quadcopter with 4 individual gas engines controlled manually - yeah right, what was amazing was that they ever got it off the ground at all.


Developer
Comment by John Arne Birkeland on July 16, 2016 at 3:45pm

Multi-copters are cheap and easy to make, making them perfect for consumer markets. But they have severe practical limitations when put to commercial usage. But for some reason, they trigger the imagination and has become a media darling. So everybody is making multi-something, fully knowing a helicopter would be the better solution.

The mechanical "complexity" in a helicopter is a solved problem. I have never heard talk about swash plate, linkage etc. failures even on dirt cheap hobbyking R/C helicopters. Electrical/servo failures seem to be the most common source of crashes. Excluding pilot mistakes of course. One could potentially argue that helicopters are more dangerous, but in my eyes the only real disadvantage is how fragile they are if you have a bad landing.

Comment by Gary McCray on July 16, 2016 at 8:41pm

Hi John,

I think Rob also agrees about the bad landings deficit.

I wonder if that problem could be reduced through some innovative design though.

Many copters already have free pivoting rotor blades which partially disconnects them from the mass of the power train.

But what if you made some sort of trigger-able clutch that could fully disconnect the motor and the other attached rotating mass.

Seems like that could both reduce the damage and increase safety as well.

Of course, you would only want it to trigger at the "right" time.

And I can see that might be a problem.

Just a thought for future concepts.

Really light rotor blades would help too, and with our modern nifty materials, that should be fairly easy.

It's the rotating mass that really chews up a heli (the bystanders too for that matter).

If you've ever seen a video of one of those giant Russian MI26 Helicopters crashing it illustrates this point very well.

Best Regards,

Gary 

Comment by Ravi on July 17, 2016 at 8:25am

for long endurances helis are still the winner. what about a 3 hrs flight. not possible with a multicopter. but yes with a gas heli. since they have a single rotor it's easy to make a drive train for the rotor.

Comment by Rob_Lefebvre on July 17, 2016 at 6:24pm

Ravi, though Quaternion in Spain are working in a qas powered hybrid-electric quadcopter that does fly for over 2 hours.

In my mind, however, you can't get past some basic math.  Let's say you have two aircraft that have the same engine, with the same specific fuel consumption.  The quadcopter has to carry around the DC generator stage, that the helicopter does not.  Plus 4 motors and ESC's.  All of that mass could be extra fuel on the helicopter. There's energy conversion losses in all of that too.  Then the heli can have much more disk area for a given frame weight.  I just don't see how a quadcopter could ever come out on top, at the end of the day.


Developer
Comment by Andy Little on July 18, 2016 at 1:30am

The killing point against RCHelicopters though is that they are scarey. When  a RC heli is flying at my local field I don't feel comfortable within 20 yards of it for whatever reason. I may be alone in that view but I don't think so . Translate that feeling into a helicopter landing in your back garden to deliver a parcel and you have a real PR problem

A quadcopter doesn't give rise to the same sort of fear since there is much less energy in the smaller blades and it is easier to provide a blade guard. 

Unfortunately it is the triumph of style over substance

Comment by Rob_Lefebvre on July 18, 2016 at 8:01am

Andy, have you ever been near a quadcopter with 28" props?

Until you have, you are comparing tangerines and grapefruit.

THAT is the number one reason for this misplaced fear of helicopters.  Because historically, the helicopters most people are familiary with, have been large, hugely overpowered super high performance sports machines.  And the quadcopters they see, are tiny little flimsy underpowered things. 

Comment by Rob_Lefebvre on July 18, 2016 at 10:40am

So I've had a chance to read the entire thing.

While I am a proponent of helicopters, I think this article gets a few things wrong.  It's a complicated topic, but I think they get a lot of the details wrong.  And I also question the claims for the ZYG800 system.  They seem to be outside what I find is plausible.  

I think the details are wrong, but the conclusion is right (just from different details).

Comment by Gary McCray on July 18, 2016 at 11:33am

@ Rob +1

The article is not well written and references a lot of irrelevant or marginally relevant information.

But as you said, the basic conclusion is correct.

The most significant danger with helis is to dissipate all that rotational energy stored in the rotors and drivetrain.

True both for damage to people and property and for damage to itself on sub-optimal landings.

It still seems to me that ultra light rotors (a lot more practical on UAV size copters than manned ones) and a dog clutched drive-train could go a long way to reducing this particular danger.

I also wonder about the possibility of being able to cause the rotors to go into a very high pitch (purposeful blade stall) or even vertical condition in the event of an imminent crash.

This would seem to ameliorate the greatest hazard relating to helis quite a bit.

Best Regards,

Gary

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