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The NASA demonstration last year in which a Bell Autonomous Pod Transport (APT) 70 cargo drone flew autonomously through the Dallas-Fort Worth metropolitan area identified gaps in command-and-control (C2) and detect-and-avoid (DAA) capabilities that warrant further study.
That’s according to the final report that Bell submitted to NASA for the two-year Systems Integration and Operationalization (SIO) activity, which aimed to help establish standards for commercial operations of unmanned aircraft in the national airspace. Bell was one of three companies that partnered with NASA on the project, along with General Atomics and American Aerospace Technologies.
In its concluding flight demonstration on Sept. 28, 2020, Bell’s APT 70 drone — which can carry payloads of 70 pounds (30 kilograms) or more — simulated a critical medical transport mission by flying a pre-programmed route along the Trinity River, including transitions into and out of Class B airspace. According to Bell’s report, of several scenarios considered for the demonstration, the medical transport mission was deemed the most challenging from a beyond-visual-line-of-sight (BVLOS) perspective due to the noisy radio frequency (RF) environment, the challenges of radio line-of-sight due to infrastructure obstacles, and the DAA complications of a low-altitude urban environment.
Numerous safety precautions were taken for the demo, beginning with careful route selection and including a visual observer in a chase helicopter to see and avoid other traffic.
Bell’s C2 package included two independent (Persistent Systems and Silvus StreamCaster) radios operating on different frequencies, a Troll Systems MT-300 auto-tracker antenna, and two Ubiquiti EdgeRouter arbitrators: one on the aircraft and one on the ground control station (GCS).
The airborne DAA system, developed by Xwing and integrated by Bell, consisted of two Echodyne EchoFlight radars, three FLIR HD ethernet cameras, and a uAvionix ADS-B receiver. Data was processed onboard the aircraft using two commercial off-the-shelf computers, with tracks, alerts, and maneuver recommendations sent to the GCS through the C2 datalink.
The demo revealed C2 technology gaps for remote BVLOS landings. According to the report, “direct line-of-sight RF links will lose link as an aircraft descends to its remote landing location unless some additional technology is implemented,” which could include a remote radio link to the GCS, satellite communications, or LTE technology. “Additional research is needed for low-SWaP [size, weight and power] technology to accomplish this task,” the report states.