Developing uncrewed R44s for crop-spraying

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Rotor

Separating the wheat from the chaff is how we harvest over 750m tonnes of the stuff every year. Primarily done by combine harvester, the machine reaps, threshes and winnows the wheat; at its heart is a series of rotors that do most of the work.

Hoping to separate themselves from rest of the field in the agricultural aviation sector is the perhaps aptly named startup Rotor Technologies. The New Hampshire-based company, through a partnership with Robinson Helicopter Company, is retrofitting helicopters to fly visual line of sight (VLOS) drone operations such as crop spraying.

Officially termed the Sprayhawk, Rotor’s craft, based on a Robinson R44 helicopter, is the largest agricultural drone available globally. It features a 120-gallon spray tank with 33ft spray booms, camera and LIDAR (light detection and ranging) sensors for detecting wires and avoiding obstacles, plus autonomous spray path and terrain following algorithms. The aircraft is currently on offer for $990,000 until mid-December – a standard 2021 Robinson R66 costs about $940,000.

Operable by two people on the ground, the Sprayhawk can spray at over 80mph for up to 50 minutes of flight time. Comparable to the capabilities of manned crop-dusting aircraft, reductions in operating costs and increased safety for operators are where Rotor hopes to capture the market.

Revolution.Aero sat down with CEO and founder Hector Xu to discuss vision, certification and commercialising their “big drones”.

Why retrofit an existing airframe?

An MIT and Cambridge University graduate, Xu got the idea for Rotor whilst training to be a helicopter pilot. “These machines have been around for 50 years, I saw an opportunity to make them much more capable using today’s technology. Sitting in the pilot’s seat I understood the critical safety component of flying helicopters and how much safe operation relies upon the skill of the pilot,” he says.

But on the other hand, Xu says there is little competition when assessing the capability of a helicopter versus, for example, an electric alternative. Having worked on a number of eVTOL concepts during his MIT years, Xu firmly believes that electrification doesn’t yet provide a solution for today.

“I think the overall trajectory is correct, but it [electrification] is obviously a multi-decade investment, for the industry and humanity. Rotor’s mission was always to make a big impact as quickly as possible. That is why we chose the retrofit approach to enhance the existing fleet,” he says.

Xu is not wrong. Since founding in March 2021, the startup has set up three R&D and production facilities at former aviation college Daniel Webster College and Nashua Airport, completed multiple flight demos with FAA authorisation, as well as announcing the collaboration with Robinson and putting its R550 platform into production this summer.

Rotor forecasts delivery of up to three aircraft based on the R550 platform to customers in 2024, with 20 deliveries targeted in 2025. Although customer demand is currently weighted toward the Sprayhawk, Rotor also offers a retrofitted R44 solution, which it calls the Airtruck, for the construction industry. Additionally, the company is developing other UAV models based on new platforms with first deliveries slated for 2026. Xu revealed the company is nearing completion of a production facility capable of turning out tens of aircraft per year.

“In our three-and-a-half-years since founding the company, I think our ability to make fast progress comes down to us not reinventing the wheel. Instead we are leveraging resources, designs and companies that already exist,” says Xu. “We work with Robinson who know how to build light aircraft. We work with helicopter operators who know how to operate. We are a sliver of technology in the middle that in some senses supercharges existing technology to make it safer, more capable and a lot more cost effective.”

The technology sliver

Put simply, Rotor makes the stuff that keeps the helicopter in the air. “The brains” Xu calls it. The engineering team rips out all of the avionics and controls from a helicopter, before replacing it with a fly-by-wire system, and communications and sensing systems it developed in-house. The firm also builds the communication and ground control systems for flight operations.

“Our big focus is on software, we build 100% of it. We leverage a lot of the great sensors that have been built for automotive autonomy. Then we build a series of critical flight components ourselves because they require a high level of reliability and design assurance. We see this as the greatest value add. Our technology provides the basis of flight elements like stability augmentation or envelope protection that keeps your aircraft safe. This means someone with a minimal amount of training can fly it,” says Xu.

Rotor has consciously kept its developmental surface area as narrow as it can. Versus a clean sheet aircraft OEM, that has to focus on myriad elements which spread resources thin, Rotor builds three blocks: a fly-by-wire system, a sensing suite and a ground control station.

Remote operations 

Operation of Rotor’s drone requires two people, a pilot and a visual observer. Restricted in commercial and civilian operations to VLOS flying and radio transmission range (about three to five miles), the platform operates in much the same way as a DJI drone except it is several orders of magnitude bigger – and therefore more effective, says Xu.

“We’ve had a huge response from the agricultural community which has seen significant adoption of drones for aerial applications like crop-dusting. But there is nothing on the market that can really meet the size of US fields. Our technology therefore has resonated with that community without needing to fly beyond visual line of sight. We don’t need to enter the national airspace, we’re able to conduct operations at low altitudes and at a very low risk level.

“Agriculture is just an example too. Our platforms are also equally suited to construction in remote areas, logistics and even search and rescue,” adds Xu.

With four aircraft constructed to date, two of which are built to production model standards, Rotor has recently had its production models approved by the FAA via special airworthiness certificate. Specifically for agriculture, Rotor’s platforms are then certified under the FAA’s 44807 Exemption. This grants operators exemption in Class G airspace at maximum altitude of 400ft in the National Airspace System (NAS).

“That exemption does not permit blanket operations, but it does allow us to fly in large parts of US farmland. By the time the next spraying season comes around – summer 2025 – we expect to have around five aircraft flying with farmers in commercial pilot programmes. The goal is then to produce 10 to 20 aircraft over winter 2025 for delivery to customers in the US and, likely, Brazil for summer 2026.”

What is next for Rotor?

Agriculture is a beachhead for Rotor, according to Xu. The firm sees crop-spraying as an ideal use case to gather data and build a safety case for other applications beyond.

“It is a no brainer, there is a large market that wants to use our aircraft. So we can cut our teeth in agriculture, accumulate hundreds of thousands of flight hours and build a safety case for the future. As we’ve seen elsewhere, getting to that hundreds of thousands of flight hours mark is a near impossible task if you’re targeting your end goal from day one. This is why this crawl, walk, run approach is existentially important if you hope to one day enter the national airspace and carry people, for example.”

Xu also says that in some senses “safety doesn’t sell”, rather it is expected. New technology needs to be safer than the one it is replacing. The real draw for customers is the cheaper operating cost even at low volumes. Versus its main competitors – the manned R44 helicopter and fixed-wing Air Tractor – Rotor’s Sprayhawk at $2.00 /acre is cheaper by about 30-40%. The R44 comes in at $3.27/acre and the Air Tractor costs $3.23/acre. Additionally, two DJI Agras drones amount to $4.87/acre.

“These reductions partly arise from the removal of the pilot, but also because we can almost double the capacity of the sprayer from 60 to 110 gallons. Then, once we receive blanket commercial approval these aircraft will be able to be operated by someone with a Part 107 drone licence, which will significantly reduce piloted related costs further for operators,” says Xu.

Currently funded by a sole undisclosed venture investor to the tune of tens of millions USD, the firm also runs a consultancy service on the side which advises helicopter operators on automation of their fleets. Xu describes the service as a “significant source” of revenue for the company as Rotor continues to grow through its pre-revenue phase for the drone platforms.

From a kernel of an idea in 2021 to delivering to its first customers later this year, Rotor has made impressive progress in setting itself up to disrupt the field of agricultural aviation. Xu is confident this trend is set to continue, positioning the company as one of two key rotors for a fruitful harvest.

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