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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I'll just leave this here. :)

@ Rob, +1!

Gary McCray said:

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.

The current rules have been working fine.  The new rules that go into effect in August for commercial operators of UAV's are a fiasco.  The only reason the FAA implemented them is due to pressure from industry people that want to sell turn-key UAV's.  So the FAA dreamed it up.

Traditionally, anything that a human can fly required a Part 61 certificate to fly it commercially.  Under the new rules all you have to do is pass the equivalent of a ground school written for a Part 61 student pilot and you are suddenly a certificated Part 107 commercial UAV pilot.  To which I say "hogwash".  There is no flight proficiency test, or skills test, nothing.  So now what do we have?  A bunch of commercial drone operators that don't have a single clue how to fly an aircraft.

So we have people flying them in cities with high amounts of RFI/EMI, we have flyaways and crashes.  Sooner or later one smashes thru the windshield of a car going down the freeway at 70 mph, or conks somebody over the head.  Keep in mind, these commercial UAV pilots that passed nothing more than a basic written test can fly aircraft up to 55 lbs.  If one that size comes down it's gonna hurt.

So then there's going to be minimum liability insurance requirements, with a bond, just like there is now with Part 135 and 121 operators, et al.

Further, it will be found in one of these crashes that it was caused by failure of a component on the aircraft that should've been replaced.  BUT - we have pilots flying them that are also their own A&P.  So some of them don't know the difference between a cracked motor mount or a loose screw.  After somebody gets killed by one and the lawsuit goes into the millions, including the manufacturer being named as a party, we're going to end up with required 50 or 100 hour inspections, annual inspections, and TBO on certain parts.  And every part put in the aircraft has to have a FAA Type Acceptance Certificate (or STC) that says it's ok to use that part in that aircraft.

In the end, the commercial manufacturers who pressured to get this stuff passed, end up shooting themselves in the foot.  They should've left it as it is now, with only professional pilots flying them commercially, instead of putting up the illusion that anybody can grab a radio transmitter and fly an aircraft - all you have to do is pass a written test.  There hasn't been any problems with the ~1,500 licensed commercial operators of UAV's in the US under the current rules, and I think the aircraft being flown could be used to much higher levels of capability with professional pilots in command of the aircraft.  But there will be once you put them into the hands of the masses.

Hi Chris,

I completely disagree that "The current rules have been working fine".

If by this you mean nobody has yet been killed under these rules, you are right, however, there is a level of practicality and fairness that is completely unmet by the current rules.

Requiring all UAV pilots to also be manned aircraft pilots is complete nonsense.

Not only is the cost totally prohibitive for those seeking to just become UAV pilots but at least one half to three quarters of what you learn is completely not germane to being a UAV pilot.

I am a non-current private aircraft pilot and I am completely sure of this.

It works great for private pilots who would like to dabble in UAV and becomes an impenetrable and unaffordable barrier for everybody else.

The very large majority of current commercial uses are going to be for Phantom sized aircraft taking photos and videos of real estate and other stuff.

While they do represent a threat, it is small, and the main thing you need to learn is what is expected of you by the FAA and the public.

Just like in a real plane, you can always choose to ignore it and wreak havoc and suffer the consequences, no amount of experience or capability is ever going to prevent that.

But presumably, in the training, the FAA is going to make sure you at least know what is allowed and what is not along with the assurance that they will come down on your head like a ton of bricks should you choose to behave otherwise.

Clearly it places the onus of being able to actually fly on the prospective pilot, but we already have exactly that situation with hundreds of thousands if not millions of hobbyist flyers.

This will very definitely be a significant improvement on that situation.

Will there be million dollar lawsuits, sure, mostly because it is new.

An automobile accident rates hardly a yawn by comparison.

But in the end the reward to risk ratio easily justifies the risk and actual damages.

If you rigorously follow the FAA's rules you are very unlikely to get into trouble.

That said, I think that the current emphasis by manufacturers (including 3DR) and DJI on the UAV's automatic qualities to the extent that they are actually trying to convince you that you really don't even need to know how to fly is unconscionable.

And I only hope that the first few of those multi million dollar lawsuits catch them as co-defendants for promoting this incredibly unrealistic expectancy in the first place.

My basic thesis is learn to fly really well manually before ever trying anything even remotely autonomous and I think that is the only rational approach.

For more advanced capabilities than are now permitted and in larger aircraft, additional requirements will also be necessary, but 107 is a really good start.

Best Regards,


Gary McCray said:

Hi Chris,

I completely disagree that "The current rules have been working fine".

Gary, I can see some of your points.

Traditionally, a new R/C pilot would join a club and take instruction from an experienced pilot before flying his/her own aircraft.  And this is where I agree 100% that the manufacturers pushing the autonomous capabilities of the aircraft, allowing anybody to fly one, borders on insanity.

What made the quad-rotors so popular is cost and simplicity, VTOL capability, and the use of onboard attitude adjustment and navigation making them easy to fly ( as long as everything works ).  But they are not that reliable.  Just go to the DJI forum and read all the "wildly takes off and crashes", "lost control - flyaway" threads.  LOL!

I don't know about a single rotor, but every multi I've flown goes into a mind of it's own if it loses the IMU and/or GPS.  A fixed-wing will continue to fly without either, properly trimmed, until it regains nav and attitude control, or the pilot takes control.  But any rotary wing is pretty much a disaster once they go "dumb" without a competent pilot on the sticks.  The most exciting one I had was my DJI Phantom FC40.  That thing would lose GPS and attitude control about every third flight.  And if I yawed it too much trying to figure out which was it was pointed in the recovery, the magnetic compass would go south too.  Bringing that thing in from a 1/4 mile away when it went "dumb" was about like herding cats.  And typically, just reboot the flight controller - unplug the battery and plug it back in again - and it was fine and got "smart" again.  DJI would release firmware with more bugs in it than a warm August night, then release more firmware that killed some of the previous bugs and let loose a whole batch of new ones.  What a piece of junk.

Seems we are back to one of my pet peeves.

The 'old-school' R/C pilots vs new generation of 'I just want to press a button and take pictures' users.

I am solidly in the pilot camp. The 'press a button' user scenario is still some ways into the future. And this causes problems since companies are already pushing hard today, selling tech that is nowhere near robust enough for inexperienced users.

Suddenly the newbie at the flying field with the cool and totally wrong EDF jet plane model that is guaranteed to crash, has become the norm. And not knowing any better mainly because companies are indirectly saying so, their are flying it wherever they feel like.

That was sort of my point on the FAA rules pertaining to commercial use of UAV's and the qualifications of the pilot.  There is no Part 61 pilot I know that would blindly accept that any aircraft can fly itself.  It's due to the training, flying real airplanes where it is grilled in that any instrument or component can fail and you still have to be able to fly the aircraft and safely land it.

Like I said, I can see Gary's points but don't necessarily agree with them when it comes to pilot qualification under the new rules.

So my prediction is that it is not going to work in the long term.  The current rules have been working fine and hold true to long-established requirements and qualifications in the aviation industry, which has a safety record second to none.  Once that is relaxed, then we have a compromise fueled only by one thing - money.  The desire of manufacturers to sell UAV's to the masses.  The consumer market is saturated.  So now they're looking to the commercial market.  But putting these things into the hands of unqualified commercial pilots is a recipe for disaster because commercial operation will typically have a higher exposure to the general public vs hobby/recreation.  If they had a program where a commercial UAV pilot would have to take a minimum number of hours of flight instruction, and be required to pass a flight competency test with an FAA examiner and qualify the pilot with ratings and limitations like the current Part 61 system, then I would see it differently.  Under Part 61, you can get a private with SEL rating.  But that doesn't mean you can hop into a AT-802 with a 1,300hp turbine and fly it unless you spend a certain number of hours of flight training in it and get a Type Rating in the aircraft.

Commercial manufacturers are going to shoot themselves in the foot when product liability lawsuits start to happen under commercial operations without scheduled maintenance requirements and proper pilot qualification.  Those two things have been the mainstay in commercial aviation safety since the 1940's.

Chris, I don't think anybody here is suggesting that UAV helicopters are going to replace the Air Tractor anytime soon.  However, at some point, the _pilot_ in the Air Tractor is going to be replaced by an autopilot.  Your career is probably fine, but I wouldn't suggest any kids today, plan on being Ag pilots.  I actually have a friend who's about 50, who's father was a tug-boat captain on the Thames.  My friend initially trained to be a tug-boat captain as well.  But after 10 years, that career path was finished as they stopped bringing freight up the Thames. He's now running an IT company.

This will happen.

I also believe Gary is right, that large UAV helicopters will be used for spot-applications.  They will not replace Air Tractors completely.  But will start stealing at least some of the business, as problems will be treated before they are farm-wide.

I'm a huge proponent of manual pilot skills, and I also think that the UAV pilots license should include some training, and UAV systems should be forced to include manual pilot controls on a proper joystick system.  However I will say, that the rate of incidents of flyaways and other problems has been greatly reduced over the past year or so.  It's really pretty rate now.  Even with DJI.  It used to be that 50% of forum posts were about flyaways.  Not so anymore.

Rob_Lefebvre said:

Chris, I don't think anybody here is suggesting that UAV helicopters are going to replace the Air Tractor anytime soon. 

Oh, definitely not.  I tried to reply inline but it didn't work for some reason.

Anyway, this has been an interesting discussion.  I learned that some folks are flying R/C helicopters with the APM/PX4/Pixhawk system.  And I think that would make an excellent platform for flying precision GPS grids for aerial imagery work.  Which means I have to explore a different aspect of aviation in the future.  Unfortunately, I have to leave this afternoon for a 10 day tour of duty in Canada.  So wanted to thank all for the quite interesting and informative discussion.

On the flyaway issue, Rob, I think probably 99% of them are pilot error.  People are flying high RFI/EMI environments, the aircraft loses navigation, and in many of the cases the pilot stands there with (usually) his lower jaw scraping the dirt and does nothing.  DJI has pretty much completely removed manual control from their products and give the pilot a false sense of security with the "GPS - Safe To Fly" green light to take off.  When it should be more like, "You have GPS lock - take off manually and then engage the autopilot".  This all gets back to the manufacturers giving pilots a false sense that the aircraft is capable of flying itself and it's "unsafe" for the pilot to assume manual control.  Even today, they just aren't that reliable.

Don't get me wrong autonomous stuff will let you do some great things, but like Arne said, at this point in time and using the systems they are using these capabilities are subject to many forms of failure.

Dependency on a GPS at the level it is currently promoted is ludicrous.

At one time, we had lots of information on this site and the wiki about multipath and signal blocking, I know, I wrote it.

But the fact is, all the newbies who go out and buy a Phantom are clueless about it, what is amazing is that their aren't a whole lot more crashes than there are.

learn to fly manually, approach any form of autonomous flight / maneuver very carefully and spend a lot of time learning how to "manually" recover from failed autonomous modes.

Currently they promote exactly the opposite, like I said, I hope the companies that are doing that are the recipients of their own completely ill advised profit serving hyperbola in the form of getting successfully sued also.

As for pilot training, the current hobby explosion of Phantom-like sales has already pushed that requirement into oblivion.

That said, I do think that it needs to be greatly revisited.

But NOT by requiring that UAV pilots become manned aircraft pilots - that is nonsense.

a LOT of the requirements are actually counter to what a UAV pilot needs to know and much of what you learn does not translate into training to actually fly UAVs.

If you are going to require flight training for UAVs it truly needs to be in UAVs, not manned aircraft.

Even FPV flying would be much better served in a UAV simulation trainer than in a manned aircraft.

As it is all the manned aircraft piloting requirement did was to guarantee that only the privileged and rich <1% would ever be able to fly UAVs.

If in the end eventually the FAA does feel it incumbent to require pilot flight training for UAVs it will be in UAVs and appropriate to the cost - reward ratio that actually works, not just a silly and inappropriate stop gap because they only currently had manned aircraft training available.

And as for heli UAVs, I am really confidant, they will eventually reemerge as a high end UAV solution that is in many cases superior to either multis or fixed wing.

The sad part of that is that the number one open source developer in that field got sidelined by 3DR who abandoned helis when they took everything in house.

Probably a simple economic decision to concentrate on multis for them, but a devastating loss to DIYD

Really sorry Rob.

My thoughts anyway.

Best Regards,


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