In 2021, he founded the autonomous helicopter company Rotor Technologies, Inc.

It turns out Xu’s near-misses weren’t all that unique. Although large, commercial passenger planes are extremely safe, people die every year in small, private aircraft in the U.S. Many of those fatalities occur during helicopter flights for activities like crop dusting, fighting fires, and medical evacuations.

Rotor is retrofitting existing helicopters with a suite of sensors and software to remove the pilot from some of the most dangerous flights and expand use cases for aviation more broadly.

“People don’t realize pilots are risking their lives every day in the U.S.,” Xu explains. “Pilots fly into wires, get disoriented in inclement weather, or otherwise lose control, and almost all of these accidents can be prevented with automation. We’re starting by targeting the most dangerous missions.”

Rotor’s autonomous machines are able to fly faster and longer and carry heavier payloads than battery powered drones, and by working with a reliable helicopter model that has been around for decades, the company has been able to commercialize quickly. Rotor’s autonomous aircraft are already taking to the skies around its Nashua, New Hampshire, headquarters for demo flights, and customers will be able to purchase them later this year.

“A lot of other companies are trying to build new vehicles with lots of new technologies around things like materials and power trains,” says Ben Frank ’14, Rotor’s chief commercial officer. “They’re trying to do everything. We’re really focused on autonomy. That’s what we specialize in and what we think will bring the biggest step-change to make vertical flight much safer and more accessible.”

Building a team at MIT

As an undergraduate at Cambridge University, Xu participated in the Cambridge-MIT Exchange Program (CME). His year at MIT apparently went well — after graduating Cambridge, he spent the next eight years at the Institute, first as a PhD student, then a postdoc, and finally as a research affiliate in MIT’s Department of Aeronautics and Astronautics (AeroAstro), a position he still holds today. During the CME program and his postdoc, Xu was advised by Professor Steven Barrett, who is now the head of AeroAstro. Xu says Barrett has played an important role in guiding him throughout his career.

“Rotor’s technology didn’t spin out of MIT’s labs, but MIT really shaped my vision for technology and the future of aviation,” Xu says.

Xu’s first hire was Rotor Chief Technology Officer Yiou He SM ’14, PhD ’20, whom Xu worked with during his PhD. The decision was a sign of things to come: The number of MIT affiliates at the 50-person company is now in the double digits.

“The core tech team early on was a bunch of MIT PhDs, and they’re some of the best engineers I’ve ever worked with,” Xu says. “They’re just really smart and during grad school they had built some really fantastic things at MIT. That’s probably the most critical factor to our success.”

To help get Rotor off the ground, Xu worked with the MIT Venture Mentoring Service (VMS), MIT's Industrial Liaison Program (ILP), and the National Science Foundation’s New England Innovation Corps (I-Corps) program on campus.

A key early decision was to work with a well-known aircraft from the Robinson Helicopter Company rather than building an aircraft from scratch. Robinson already requires its helicopters to be overhauled after about 2,000 hours of flight time, and that’s when Rotor jumps in.

The core of Rotor’s solution is what’s known as a “fly by wire” system — a set of computers and motors that interact with the helicopter’s flight control features. Rotor also equips the helicopters with a suite of advanced communication tools and sensors, many of which were adapted from the autonomous vehicle industry.

“We believe in a long-term future where there are no longer pilots in the cockpit, so we’re building for this remote pilot paradigm,” Xu says. “It means we have to build robust autonomous systems on board, but it also means that we need to build communication systems between the aircraft and the ground.”

Rotor is able to leverage Robinson’s existing supply chain, and potential customers are comfortable with an aircraft they’ve worked with before — even if no one is sitting in the pilot seat. Once Rotor’s helicopters are in the air, the startup offers 24/7 monitoring of flights with a cloud-based human supervision system the company calls Cloudpilot. The company is starting with flights in remote areas to avoid risk of human injury.

“We have a very careful approach to automation, but we also retain a highly skilled human expert in the loop,” Xu says. “We get the best of the autonomous systems, which are very reliable, and the best of humans, who are really great at decision-making and dealing with unexpected scenarios.”

Autonomous helicopters take off

Using small aircraft to do things like fight fires and deliver cargo to offshore sites is not only dangerous, it’s also inefficient. There are restrictions on how long pilots can fly, and they can’t fly during adverse weather or at night.

Most autonomous options today are limited by small batteries and limited payload capacities. Rotor’s aircraft, named the R550X, can carry loads up to 1,212 pounds, travel more than 120 miles per hour, and be equipped with auxiliary fuel tanks to stay in the air for hours at a time.

Some potential customers are interested in using the aircraft to extend flying times and increase safety, but others want to use the machines for entirely new kinds of applications.

“It is a new aircraft that can do things that other aircraft couldn’t — or maybe even if technically they could, they wouldn’t do with a pilot,” Xu says. “You could also think of new scientific missions enabled by this. I hope to leave it to people's imagination to figure out what they can do with this new tool.”

Rotor plans to sell a small handful of aircraft this year and scale production to produce 50 to 100 aircraft a year from there.

Meanwhile, in the much longer term, Xu hopes Rotor will play a role in getting him back into helicopters and, eventually, transporting humans.

“Today, our impact has a lot to do with safety, and we’re fixing some of the challenges that have stumped helicopter operators for decades,” Xu says. “But I think our biggest future impact will be changing our daily lives. I’m excited to be flying in safer, more autonomous, and more affordable vertical take-off and-landing aircraft, and I hope Rotor will be an important part of enabling that.”