Why aren't there more single rotor drones out there?

Hello all,

I have just recently joined this forum and find it fantastic what you guys are doing, very nice job.

There is one question going around in my mind for quite a while now: Why aren't there more single rotor drones out there? Though some posts here touch on that topic, I could not find any post discussing this matter in more detail. There is probably no better place to get some informed opinions on this than this forum here, so I would love to hear your take from any possible perspective you might offer.

In my mind there are many points speaking for a single rotor design. Though its implementation might be more difficult. A single rotor drone could be designed to be a lot more energy efficient than a multi-rotor design, resulting in longer battery life. It could also be designed for higher payload and high-altitude capabilities (e.g. high-payload in mountains etc.). In addition to that they could offer higher flight stability, increasing their application potential in strong winds (e.g. inspection of wind turbines). So, what do you think is the reason why there aren't more single rotors out there?

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3d helis aren't the only dangerous ones around, the Yamaha RMAX has already killed someone...

The RMAX has been operating commercially since 1997, and there are currently more then 2500 of them in operation around the world. And in all that time there has been a single fatal accident. The alternative is manned crop dusting where pilots die every year.

John Arne: Interesting. I had no idea there were so many. Where did you get that data?

John Arne: Interesting. I had no idea there were so many. Where did you get that data?



John Arne Birkeland said:

The RMAX has been operating commercially since 1997, and there are currently more then 2500 of them in operation around the world. And in all that time there has been a single fatal accident. The alternative is manned crop dusting where pilots die every year.

The little RMax came from Japan for spraying rice paddies.  Here in the US we make 2 mile passes at 140 kts and cover 5,000 acres in a day, with ferry time, with one aircraft.  And have application precision of +/- 6 inches.  Due to the scale of the job, there's not going to be any UAV's doing aerial application in the US except in experimental, or very small scale situations.  There's a few R-Max's doing application on vineyards in the US, but that's about it.  You get out on the Great Plains where the state of Montana is bigger than the entire country of Japan, and you'd need 10's of thousands of them to do what the current fleet of aerial application aircraft does.

I've been an aerial applicator for 28 years. In our business helicopters are considered to be a basket of spare parts flying in formation. The business has moved to turbine-powered fixed-wing aircraft, which are a huge step forward from the old Cessna AgWagons and Grumman Ag Cats that we used to fly. Helicopters in the aerial application business are pretty much a no-go since the only pilots that will fly one are desperate to get a flying job, and helicopters spend more time in the hanger with an A&P bolting on parts than they do flying.  They're simply too expensive to operate.  Two companies - Air Tractor and Raven Industries - pretty much revolutionized aerial application.

Hi Chris,

I agree with you - sort of.

It's certainly true that the bulk of existing spray applications and methods are well served by Air Tractor's turbine fixed wing.

And that in Japan and the rest of the world it is small rice "farms" and other small scale farms that are served by the RMax.

But here in the US Ag needs also seem to be shifting from one blanket overall spray system to a lot more spot remediation and special needs even on the big crops.

I don't think Air Tractor is going away any time soon, but I do think there will be a steady growth of applications for RMax like systems as well.

As you said, the Vineyards were an early adopter (led by 3DR for that matter).

And they are a excellent candidate, because, they can really make use of vine by vine, row by row and section by section analysis and treatment.

A fully automated system that could perform that kind of operation could very substantially increase yields and quality and in grapes, that is big money.

Not to mention tobacco or these days more politically correct cannabis.

Still miles to go, but the first steps are already taken.

Best Regards,

Gary



Gary McCray said:

Hi Chris,

I agree with you - sort of.

It's certainly true that the bulk of existing spray applications and methods are well served by Air Tractor's turbine fixed wing.

And that in Japan and the rest of the world it is small rice "farms" and other small scale farms that are served by the RMax.

Well, actually the AT-series does about 95% of the application in New Zealand, Europe, South America, Saudi Arabia, South Korea and China too, About 15-20 years ago we tried helicopters and they were a disaster.  The choppers can't lift the payload, at least not anything you can afford to insert the key in the switch, when you compare it to the 800 gallon hopper on a AT-802.  So with the fixed wing being able to hit 160 acres in one flight, the choppers spend over twice the time in ferry to go reload.

The second problem was that the choppers can't produce enough airspeed to drive the ram-air turbine on the pump.  So that means an electrically driven pump, and the associated generating equipment on the engine, on a chopper.

The third problem was that they don't hold up to the abuse. Operational cost was over triple that of a fixed-wing per hour.  And with application efficiency less than half of a fixed-wing, the cost per acre was astronomical to operate them.  So it was short-lived.  There's a few die-hards that got more dollars than sense that fly them.  But they are few and far between.

You'll find the same thing in agricultural aerial imagery, survey and scouting work.  I am flying a quad-rotor UAV, which is working but horribly inefficient. I've been looking at different options for quite awhile. But the commercial offerings in agricultural autonomous UAV's are primarily fixed-wing aircraft and not rotary wing.  The one and only reason I fly the quad-rotor is because of the FAA requirement that the aircraft remain in VLOS and there's not a lot of options for a fixed-wing for landing on most of the jobs I go to.  I have a problem with crash landing a fixed-wing airplane carrying a $3,000 NVDI camera.  If the FAA every grows some common sense so we can fly autonomous flights with the aircraft out of sight and out of control radio range so we can take off from a nice landing strip and fly out 20 or 30 miles, or cover 2,000-3,000 acres in a flight, then things will be different.  But at the present, that's not the case.  If that ever does come to pass in the US, I'm sure it will have all the same requirements as certificated aircraft flown commercially, including annual and 100hr inspections, etc..  I see it as being able to be done safely with flight plans filed with ATC or NOTAM's posted at local airports both on paper and UNICOM, and routing that takes the flight over only open areas that are uninhabited.  The FAA works more on knee-jerk reactions a lot of times.

At present, probably one of the more capable agricultural UAV's is the PrecisionHawk Lancaster.  I believe, but am not totally sure, that the Lancaster uses APM.   PrecisionHawk also offers a multi-rotor solution based on the DJI Matrice platform.  I'm currently flying a DJI, but on the current Section 333's you are limited to whatever aircraft you got approved.  In August I can fly my new one without jumping thru a bunch of hoops, which I am working on in my shop - and the new one is going to be APM powered.  The bottom line is that I will continue to fly a multi-rotor for now, but I am looking at different options for scouting and survey work.  And the UAV is DEFINITELY safer and cheaper to fly, per acre, than a Skylane.

Chris Anderson said:

John Arne: Interesting. I had no idea there were so many. Where did you get that data?

Found it in a random search so not confirmed of course.

http://www.helis.com/database/model/1468/

Chris Olsen:

I totally understand your point about RMAX not being practical for large areas.

My point was about safety. A drone can theoretically operate 24/7 (excluding refueling) and it does not matter if it falls down, unless by some freak chance there is a person just at the spot where it goes down. Unmanned will by definition always be safer then any manned vehicle. In the end practicality then becomes the decider when choosing between the two.

John Arne: I actually know the Yamaha guys and could check, but if that number is right I'll bet 2,000 of them never left Japan. I only know of a dozen in the US and they're all used by research universities and NASA.



Chris Anderson said:

John Arne: I actually know the Yamaha guys and could check, but if that number is right I'll bet 2,000 of them never left Japan. I only know of a dozen in the US and they're all used by research universities and NASA.
Well, maybe a little clarification on that.  They just got a Part 137 (for ag use) about the beginning of this year, which requires a certificated aircraft and a commercial certificate or ATP to fly it.  The UCANR extension is involved with the one Silverado is experimenting with in California in their vineyards.  But Yamaha owns the aircraft and right now it is being flown on a limited experimental basis as a feasibility study under scrutiny of USDA and state officials.  That is the only one I know about that has been flown commercially in the US.
Otherwise there are lots of UAV's being flown in the US for agricultural scouting and survey work, carrying cameras.  Not all are being flown legally (under the current rules).  AGCO was selling the Solo as an agricultural imagery platform but I don't know anybody in the US that is flying one.  DJI Phantom FC40's, 2's and 3's and Matrice aircraft are the ones I've primarily seen in multi's.  As of August 22, that market should open up a bit due to relaxed requirements on a Part 61 certificate to fly aircraft with a takeoff weight <55lbs for commercial purposes.

Hi Chris (both),

As for the US, probably right, flying one of those Yamaha's here right now is nearly impossible regulation wise, wrong weight and FAA not inclined to give simple go ahead for them.

But I have heard at least some of them are in use in South  America and some assorted smaller countries and island nations, not surprisingly in small crop, especially rice applications.

And I do understand they are fairly reliable and much, much lower cost than a useful manned helicopter, both purchase and upkeep.

Not so good for delivering large multi-hundred gallon loads though.

Still, that or something with similar capability and fully autonomous probably will end up being a very important Ag tool - eventually.

Best,

Gary

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