On Wednesday, Nov. 20, a couple hundred people gathered in front of a hangar at Perot Field Fort Worth Alliance Airport in Texas. They were there to watch a test flight of Rotor Technologies’ Sprayhawk — an uncrewed agricultural helicopter based on the Robinson R44 — and many of them had come directly from the National Agricultural Aviation Association’s annual expo in downtown Fort Worth.
The Sprayhawk fired up its Lycoming IO-540 engine and its blades began turning — a normal start, with the notable exception that the pilot, Joao Magioni, was sitting in a trailer behind the aircraft. After warming up for a minute or two, the unoccupied helicopter picked up into a high hover, then made a few passes back and forth over the ramp. The flight area approved for it by the Federal Aviation Administration (FAA) was limited and marked with traffic cones, but it had just enough space to demonstrate the use of its 33-foot (10-meter) spray boom system, which emitted a shower of water that shimmered in the late afternoon sun.
The roughly five-minute flight was the first public showcase of the Sprayhawk, which can carry up to 110 gallons (around 415 liters) of liquid, making it one of the largest commercial uncrewed aerial vehicles (UAVs) in the world. Yet the development was arguably more evolutionary than revolutionary, because except for the absence of the onboard pilot, nothing about it was unfamiliar to the helicopter operators in the crowd.
“As a helicopter operator, I don’t look at this as a threat,” said Helicopter Institute president Randy Rowles, who co-hosted the event along with Hillwood, the real estate developer behind Alliance Airport. “I look at it as a dull and dangerous type of operation solution, and one that we can get to market. And as an operator, having the same helicopter that I’m operating every day and turning that into an uncrewed vehicle, that makes a lot of sense to me.”
Nashua, New Hampshire-based Rotor’s evolutionary approach to deploying autonomy in existing aircraft is not unique. On the fixed-wing side of the industry, startups Reliable Robotics and Merlin Labs are both working to develop autonomy solutions for the workhorse Cessna Caravan, initially for civil and military cargo missions. In the vertical-lift sector, however, eVTOL developers have captured most of the investment and attention with radically new aircraft designs that are primarily focused on passenger transport.
Many of these companies are using remotely piloted aircraft for flight testing and aim to certify autonomous versions of their aircraft eventually. But in the U.S. and Europe, the regulatory barriers to certifying uncrewed aircraft are steep, which is why most Western eVTOL developers plan to launch commercial operations with onboard pilots first.
Rotor founder Hector Xu also envisions a future world where autonomous aircraft are routinely used to carry passengers. In the meantime, though, he’s starting at the other end of the spectrum, with a focus on “dull and dangerous” missions like spraying that do not require aircraft certificated for passenger-carrying flight. This is similar to the approach of California-based Pyka, although that startup has developed an electric fixed-wing aircraft for spray and cargo missions.
In the U.S., Rotor expects the Sprayhawk to operate under a Section 44807 exemption from the FAA, which is provided on a case-by-case basis to drones that exceed the 55-pound (25-kilogram) weight limit specified in 14 Code of Federal Regulations Part 107. Like the R44 Raven II it is based on, the Sprayhawk will have a maximum gross weight of 2,500 lb. (around 1,135 kg).
“We’ve worked with Robinson Helicopter Company to do a lot of our development, and we’re working with them even more in the future as we move towards production,” Xu said at the Fort Worth event. “We’ve replaced all of the flight controls, all of the avionics . . . with flight computers and GPS and sensors. And we’ve also loaded up the aircraft with cameras and lidar sensors.”
The fly-by-wire Sprayhawk has an autopilot and stability augmentation system to make it easier to fly than a conventional R44. Its remote pilot station has standard helicopter flight controls — cyclic, collective and pedals — although the cyclic is a traditional floor-mounted design, rather than the T-bar cyclic in the R44.
Two screens display video feeds from the front and sides of the aircraft as well as a representation of all flight instruments, gauges and circuit breaker status. An audio feed provides the pilot with additional situational awareness, while the buttons and switches that are typically on the center instrument panel have been moved to a side panel.
Command and control is currently provided by four redundant links, including two ISM radio links and two LTE links. Because of the size of the crowd in Fort Worth, attendees were asked to turn off their cell phones as a precaution to reduce interference risk during the flight test, but Rotor said this will not be necessary for normal operations. The company has ongoing and planned upgrades to its communication systems including smarter bandwidth management across multiple links, flexible options of LTE carriers based on geolocations, and satcom options such as onboard Starlink.
The current recommended operating range for the Sprayhawk is five miles (eight kilometers) within line of sight, but Rotor believes this range will increase in the near future with technology upgrades and regulatory approval. Should all links to the ground station be lost, the Sprayhawk will hover in place while attempting to re-establish a connection; if unsuccessful, it will return to the take-off location and land autonomously. Rotor said it is working with partners to refine additional options depending on the mission phase and fuel state.
Earlier in November, Rotor announced a partnership with AG-NAV to incorporate the latter’s precision navigation and flow control technology on the Sprayhawk, which will enable automated aerial application using pre-defined spray patterns. Rotor plans to continue adding more autonomous functions to the aircraft, and over time will be “rolling out software updates as our autopilot gets more advanced and more intelligent,” Xu said. Yet, at least in the near term, he emphasized, “our goal isn’t to replace the pilot. Our goal is to make them more capable and safer and have an easier, happy life.”
Rotor initially planned to use only new R44 cores from Robinson Helicopter Company to create its Sprayhawk and a cargo-hauling variant called the Airtruck. However, Xu announced in Fort Worth that Rotor will also be offering a retrofit option due to demand from operators like Rowles, who plans to convert one of his existing R44s into a Rotor UAV. Xu told Vertical that retrofits will be available for the R44 Raven I as well as the Raven II.
New Sprayhawks (including the spray tank, boom and navigation package) will be priced at US$1.5 million, while the retrofit package will cost $700,000. Through Dec. 15, 2024, Rotor is offering special introductory prices of $990,000 and $525,000 for new and retrofit Sprayhawks, respectively. (List and introductory prices for the Airtruck, which does not include a spray package, are $1.35 million and $850,000 new, and $550,000 and $375,000 as a retrofit.)
“Agriculture is a really, really important focus area for us,” Xu said. “Of the first 10 or 20 aircraft that we hope to deliver, I think the majority of them will actually end up in the Midwest doing aerial application, perhaps in Brazil as well.”
Rotor now plans to embark on a joint development program with established aerial applicators, working closely with these early adopters to refine and stress-test the Sprayhawk before rolling it out more broadly. The company expects to achieve initial commercial operational approvals by early next year and aims to deliver its first retrofit aircraft in 2025, followed by new-build Sprayhawks by early 2026.
“It’s one thing to do a little five-minute hover on a nice calm day, on a sunny day in Texas,” Xu told the crowd in Fort Worth. “It’s another to operate from dawn to dusk in a harsh chemical environment, in all sorts of wind conditions, doing an extremely challenging mission where you’re taking off and landing from trailers. We are not there yet, and this is what the joint development program is about — that we’re able to work with the best people in the industry to help us make this product fit for your needs and fit for your operations.”
