The advent of remotely piloted unmanned aerial vehicles up to and including a modified Robinson R44 promises to usher in a new era of crop dusting and other key agricultural tasks. Gideon Ewers reports on the drive towards certification.
This article was published in the February/March issue of RotorHub International. To receive more articles like this, apply for your complimentary subscription.
The advent of remotely piloted unmanned aerial vehicles up to and including a modified Robinson R44 promises to usher in a new era of crop dusting and other key agricultural tasks. Gideon Ewers reports on the drive towards certification.
When I was a boy, which to me seems quite recent but was in the harsh light of reality half a century ago, nearly all my spare time was spent hanging out down at the airfield, which in those days was quite a ways out from the city but today has almost been swallowed up by the Borg-like expansion of Houston. (There remains the one paved runway bravely hanging on, but the pattern of grass runways is long gone.)
We had a sort of unspoken agreement, my father and I, that for the completion of tasks like cleaning out the hangar, washing the plane or some other task, I would earn the price of a cold glass of root beer at the airfield greasy spoon café. Let me tell you, the taste of cold root beer on a hot day is truly nectar of the gods.
At Clover Field, because that is what it was called back then (nowadays it has a far less sylvan handle), there was an aerial applications company – or as we called them in those less sophisticated times, crop dusters.
Crop-dusting was seen very much as the last bastion of the silk-scarved devil may care barnstorming sepia-tinted pilots of an even more bygone age. They flew open cockpit biplanes for god’s sake!
Don’t forget that while fixed-wing arrivistes like the Ag Cat, Pawnee and Cessna 188 were beginning to make an appearance, at that time and in our corner of Texas the venerable Boeing-Stearman was still the industry standard.
This had a chemicals or seed hopper in place of the forward cockpit and the original 225 horsepower Lycoming or Wright engine replaced with a Wasp Junior putting out 450 hp to haul a full load out of a dirt road repurposed as an air strip on a summer Gulf coast day.
(I did hear that someone had put in a 500 hp engine, but maybe that was the stuff of legend.)
On the rotary side of the house, they had a brace of Bell 47s. (“Hey, M*A*S*H helicopters!” As I say, this was the 1970s.)
As I recall, the Boeing-Stearmans did the bulk of the taskings, with the Bell 47s used for more specialist tasks such as, say it quietly, applying DDT to orchards and the like. It was hard work for tough men who, like medieval peasants, seemed to have a life that was demanding, brutish and all too often short.
Most of the time the aircraft would return in the gloaming of the evening, having as the vernacular had it “worked a spread”.
But sometimes that return might be the arrival of the crumpled remains of a Stearman arriving on a flatbed truck for salvage and disposal.
Most often, the guy who had been flying the now wreckage would reappear on crutches or sporting a sling, but for others it would be “a shame about Pete”.
With its pilot remaining on the ground, Rotor Technologies’ Sprayhawk has the advantage of an extra 150 to 200 pounds of payload.
Rise of the rotorcraft – How helicopters changed agricultural aviation
Even at that tender age, since the Bell 47s always seemed to be in one piece, it occurred to me that helicopters might in fact be a better option for agricultural work than fixed-wing aircraft.
It turns out I was not alone in thinking that, as helicopters have since progressively made inroads into the “ag” flying space.
Today a variety of light helicopters are used in a broad spectrum of agricultural work, from aerial applications of fertilisers, seeds or pesticides – though the latter has been banned in the European Union since 2009.
H125s, B206s, MD 500s, Schweizer 300s, R44s and yes, even the legendary Bell 47s are the weapons of choice for agricultural contractors.
Unquestionably, the R22 has become the go to aircraft for Australian cattle and sheep farmers, with the Robbo supplanting horses as the jackaroo’s mount of choice for mustering, fence-checking and an array of other tasks.
It makes complete sense. You don’t need to fashion a landing strip, which may be some distance from the fields to be worked, and consequently more flight time is taken with spraying versus transiting.
Given the propensity of fields to have unhealthy things like trees or power lines at their edges, the advantages of the greater the manoeuvrability of helicopters are obvious.
Of even more benefit to the end customer farmer is the fact that the speeds at which the application can be laid down are far more variable.
Going unmanned – The Rise of UAVs in modern agriculture
In recent years, small Unmanned Aerial Vehicles (UAVs) have arrived on the scene, and they have proved invaluable for a variety of tasks.
As a result, the take-up has been impressive. In fact some estimates put the number of UAVs in agriculture at over 200,000.
While the bulk of these are quite small drones, there are a significant number of larger drones tasked with jobs that might have been thought the preserve of manned VTOLs.
Even so, the payload limits for those UAVs have necessarily limited the size of field that can effectively be worked.
Having been stripped of its flight controls and hydraulics, the R550 is a pure fly by wire aircraft with a net empty weight loss of 100 pounds.
Until now, that is.
In 2021, post-pandemic, the New Hampshire-based start-up Rotor Technologies began working on the development of a large helicopter UAV.
But their goal, at least at first, was not the ag market, as company founder and CEO Hector Xu explains.
“We built this fairly general-purpose thing, an unmanned helicopter. But the number of inquiries we had from the agricultural world saying ‘Oh, I’d like to use this for crop-dusting, can I use this for crop-dusting, can I use this for spraying?’ was just overwhelming. And I think earlier this year we decided we should respond to that.”
As a result of that interest the company announced the Sprayhawk variant of their R550 UAV, itself based on an R44 airframe.
Essentially the R550 becomes a Sprayhawk in exactly the same way that a stock R44 is modified for applications work with the addition of tanks, booms and pumps.
The advantage the Sprayhawk has over an R44 is that with the pilot remaining firmly on the ground remotely operating the aircraft, another 150 to 200 pounds of payload becomes available.
On top of that, with the removal of the flight controls and hydraulics, the R550 becomes a pure fly by wire aircraft with electromechanical actuators, resulting in a net empty weight loss of 100 pounds.
The mission, says Xu, is making a good product better.
“Robinsons are really gaining popularity in the aerial applications market and that’s because of their cost-effectiveness. They’ve built a reliable low-cost platform that they are able to deliver at scale, which was very attractive to us. They were receptive to working with us and we do work very closely with them.”
Another part of the mix is Rotor Technologies’ recent partnership with agricultural navigation system providers AG-NAV. This will be vital to the effectiveness of the Sprayhawk system, as Xu explains.
“They make what we believe is the best system that exists. You have a mission management system that is cloud-based and links in with the flow control hardware which is cloud-based and ultimately allows us to build a system that is ready to spray out of the box.”
Xu says this is what potential customers are after, a system that is ready to go.
Making the case – The value of unmanned helicopters in agricultural operations
Another benefit compared with crewed aircraft is that the operator need not hold a CPL(H) – something that in the current climate of pilot shortage may resonate with operators.
“Because we have a level of autonomy, and the protections of fly by wire, it means that less skilled operators will be able to fly the aircraft. Not unskilled – they will need to have skills, this is still an aircraft – but not the kind of skill and experience you need for a CPL(H) who typically flies agricultural missions.”
Xu is quick to point out that this is an ambition for the future, once more operational experience has been gained with the aircraft.
“As it stands, we are talking about a certified CPL(H) as the operator, but that’s certainly the trend we have seen with smaller drones and larger UAVs – and that is the case that we are making to the FAA.”
Ultimately, Xu argues that being a remotely operated uncrewed aircraft is the thing that is going to deliver the safety and operational flexibility, but from a lower pilot training requirement.
He stresses that for now a lot of unknowns remain thanks to the FAA’s slow progress in the development of regulations and standards for larger uncrewed aircraft.
“We’re looking closely at the proposed Part 108 rules as well as the agricultural exemptions. There are a lot of precedent-setting approvals for the use of large UAVs in agriculture. In fact, agriculture is probably the single place where there are the most large UAVs operating.
“We still need to have these things approved for agricultural usage, so this is an ongoing effort. But what’s great is that there’s a very, very strong safety case, which is that we’re operating at low altitudes over unpopulated areas without anyone in the cockpit.
“As I mentioned, there’s also a lot of precedent, plus what we think is particularly compelling is we have an airframe that has millions of hours of reliable operation. All we are doing is adding a remote piloting capability on top.”
“Our ambition is to work with the best operators here in the US and then around the world.”
Hector Xu, founder and CEO, Rotor Technologies
Gaining approval – Certification Challenges and FAA Regulation Updates
For now, the Rotor Technologies aircraft remains in the “Experimental” category, which places limits on the aircraft and the tasks it can perform.
Does the pace of the FAA concern Xu?
“In defence of the FAA, there is a lot at stake and they do have to be cautious, but the FAA is rational and because of the nature of agriculture, remote locations and low altitude operations, they will move faster than they would for an aircraft expected to operate in an urban environment. We’ve seen it already with the approvals they have given not just in test ranges but with some large area approvals for ag operations.”
Setting aside the approvals process, what does the customer base look like from Rotor Technologies’ perspective? After all, the price of a new Sprayhawk tops USD 1.5 million?
“I think you are talking about large farms,” says Xu. “Conglomerates and co-ops of a scale that makes owning an aircraft viable is where you see the direct customers come from, but the majority will come from operators providing contract services.”
Is there a temptation to cut out the middleman and like Joby in the eVTOL space have a builder/operator model?
“No,” Xu says firmly. “We are a developer and we want to be a manufacturer. We looked at it, of course, but the vertically integrated model makes sense for us right now. Our ambition is to work with the best operators here in the US and then around the world.”
According to Xu, the response for the Sprayhawk has been very positive. The company has been on the read with the aircraft and it made a flying debut at the Ag Aviation Convention in Dallas in November of last year, which it says resulted in a bubble of excitement from the farming community.
Does that not present the spectre of a difficulty in scaling production to meet demand, especially when the demand for the donor airframe is booming?
Xu is blunt. “Yes, I do have concerns. We have a pretty significant demand, and like you said there is a significant demand for both engines and airframes, actually. I’m working closely with Robinson to secure a supply of airframes. But that is where the retrofit programme has help too.”
In mid-2024, Rotor Technologies announced that it was launching a retrofit programme where owners of R44s could convert their aircraft to R550s, including Sprayhawks.
This offers the advantage of not only avoiding the wait for a new donor airframe but also represents a USD 700,000 saving versus an aircraft with a new airframe (which have a 2024 list price of USD 1,500,000).
According to Xu, that decision too has met with a positive response.
Real world development – The Future of Agricultural Operations for UAVs in 2025
So what then does 2025 look like for the programme? The answer is that Rotor Technologies expects to have up to five aircraft flying with their early customers, who will be operating them under the Experimental category.
Rotor Technologies has recently partnered with agricultural navigation system providers, AG-NAV
The important thing, says Xu, is that the company will be able to carry out development in the real world in real environments.
“We’ll be out there spraying stuff and that is very exciting – building that operational capability. We’ll also be working on the ramp-up of the production side too. There will be a lot going on.”
It’s given me pause, for sure, thinking about the crop duster in the second quarter of the 21st century.
The operator of a Sprayhawk spraying for boll weevils in the cotton fields on a delta day with temperatures approaching 100 Fahrenheit and humidity of 98 per cent, sitting in their air-conditioned van not wearing a helmet, not inadvertently ingesting chemicals, is going to have a rather more comfortable and less dangerous life than those Texas crop dusters of my childhood.
The farmers can look forward to a more efficient application too, but I do wonder if that glass of ice-cold root beer at the end of the day will taste anywhere near as good.
Thank you for reading our ‘Agricultural Operations’ article. You may find these news stories interesting:
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