Engineers at Honeywell Aerospace have developed a compact radar system intended to help urban air mobility (UAM) vehicles quickly advance toward autonomous flight.

The RDR-84K system, designed by a team at Honeywell’s Urban Air Mobility and Unmanned Aerial Systems unit in Phoenix, is currently being tested on a drone.

The project team spent most of 2021 building the algorithm and beginning to flight-test the unit in real-world conditions. The company’s goal is to build a system useful for air taxi and UAM operations.

“We are interested in how… the aircraft [is] going to de-conflict between a drone and manned vehicle,” Lawrence Surace, principal scientist for advanced technology strategy at Honeywell Aerospace, tells FlightGlobal on 12 April. “In December, we were successful at detecting an intruder drone and steering around it autonomously.”

RDR-84K radar system_2

Source: Honeywell Aerospace

Honeywell Aerospace last year successfully tested its new RDR-84K radar system on a drone

The unit, housed in a 3D-printed frame about the size of a large paperback book, can detect targets the size of a King Air aircraft from about 1.7nm (3km). It can detect a helicopter from about 3,300ft and identified a smaller drone from 1,000ft, engineers say.

Honeywell is a leader in building radars for larger commercial aircraft, so the project was not launched in a vacuum. What’s unique is the RDR-84K’s small size and powerful capabilities.

“We shrunk it”, so it can be used on a new generation of aircraft, says Surace. “This radar is specifically designed for detect-and-avoid, but it also has other features, like ground mapping, weather detection, obstacle detection on the ground [and] air-to-air and air-to-ground detection of multiple targets.

“Air-to-air [detection] is a very challenging environment because the radar needs to have a lot of information on its own position to be able to take over the drone and steer it in the right direction,” Surace says. “It’s a very complex algorithm that we are implementing.”

The unit weighs about 1.4kg (3lb). Engineers are working on a next iteration that will weigh half that. They expect to have it ready for testing this quarter.

Honeywell aims for the technology to be integrated onto delivery drones by 2025.

“We can network up to seven radars on a vehicle, for 360-degree coverage. A lot of our customers are asking for one that points straight out and one that’s cantered down 45 degrees so, when the aircraft is coming in for a landing, they can take advantage of our terrain-mapping capability.”

Radar, Surace says, is more reliable for detect-and-avoid than lidar-based systems. Lidar, which stands for light detection and ranging, uses a laser to make 3D measurements of objects.

“With a radar, you don’t have light issues. You can see at night. You don’t have smog, fog, any of those issues that you’d have with a lidar light-based system. Radar is sort of the all-weather, all-capability solution,” he adds.

With the system having proven its mettle in a basic head-on collision scenario, the next step of flight testing will involve more-complex flight scenarios.

“We’d like to do multiple drones in multiple different scenarios. [The unit] can detect up to 30 targets within its field of view and track 30 targets at the same time. So we’d like to throw a number of vehicles at it,” he says. “Now’s the time to really test it out, stretch its legs and see what it can do.”

There are numerous applications for this kind of radar, engineers say, including search-and-rescue at sea missions, or mapping dangerous weather fronts and microbursts.

For UAM vehicles, the system would be useful for critical phases of flight like take-off and landing.

Due to the physics of radar capabilities, it would be impractical and cost-prohibitive to outfit small UAM vehicles with large, heavy radar systems that can detect and avoid conflicts throughout entire flights. Therefore, Honeywell engineers envision the RDR-84K system as part of a larger ecosystem that also relies on ground-based systems.

“Strategic deconfliction will happen on the ground, from a control station, much like air traffic control does it today,” Surace says. “This radar would come in handy for applications from zero to 400ft, at take-off or landing, for example.” The system could detect a rogue drone or an obstacle as the vehicle climbs or descends.

The radar is not designed to distinguish whether other objects are, for instance, birds or aircraft. It can also detect ground objects like buildings and trees.

“The algorithm says, ‘Okay, there’s something out there, and I know it’s moving directly at me at this speed, and I know I’m moving at this speed.’ So it starts the calculation that says, ‘I have to turn this fast in this direction, by this time, in order to miss that target.’ And these calculations are going on continually,” says Surace. “If there is something out there that’s big enough to see, it’s going to avoid it.”

Honeywell has said it is working with air taxi developers Lilium and Vertical Aerospace on avionics and flight control systems for those companies’ UAM concepts. It is also developing flight control and satellite communication and sensor systems for a heavy-weight cargo drone being developed by Pipistrel, recently acquired by Textron Aviation.