After completing a fourth series of test flights last month, a NASA-led team that is designing a “detect-and-avoid” (DAA) avionics and radar suite is expected to report back soon. DAA is meant to prevent an unmanned aircraft system (UAS) from colliding with other aircraft. The flights of NASA’s Ikhana UAS and other testing and simulations have contributed to the development of minimum standards for a working DAA system.
Scheduled from late April through June, the twice-per-week test flights at NASA Armstrong Flight Research Center in Edwards, California, pitted the Ikhana against manned “intruder” aircraft. Data sent from sensors on the Ikhana, a General Atomics Predator B derivative, was used to assess conflict detection and alerting algorithms in software that provide maneuver guidance to a ground operator. The Ikhana was fitted with a representative DAA system consisting of a General Atomics “Due Regard” air-to-air radar, Honeywell advanced TCAS II processor and BAE Systems ADS-B transponder.
The manned-unmanned encounters have been flown under the umbrella of NASA’s UAS Integration in the NAS (National Airspace System) project, initially a five-year effort through September 2016 that has been approved for another three and a half years. NASA is sharing the findings of the research with RTCA Special Committee 228 (SC-228), which is developing minimum operational performance standards (MOPS) for both the DAA and command and control (C2) aspects of unmanned aircraft on behalf of the Federal Aviation Administration. The MOPS will inform technical standard orders (TSOs) the FAA issues, which specify requirements for manufacturers to build equipment.
NASA engineers summarized other research activities of the project during the Xponential conference hosted by the Association of Unmanned Vehicle Systems International (Auvsi) in New Orleans in May. In addition to the Ikhana flights, NASA and Rockwell Collins (Chalet B14, Hall 4/A70) have developed prototype line-of-sight data link radios operating in the L- and C-bands, providing CNPC, or control and non-payload communications, between a UAS and its ground station.
The space agency performed “channel characterization” flights for the data link radio with its S-3B Viking twin-engine jet. It installed two CNPC ground stations in Cleveland and Albany, Ohio, and flew more than 60 mission flights with 200 hours of data collecting. “NASA had a lot of impact on the C2 MOPS. We were the only prototype system for that,” said Jim Griner, NASA Glenn project engineer for communications.
A modeling and simulation environment called the Airspace Concept Evaluation System hosted a NAS-wide simulation, incorporating three months of historical radar data provided by the U.S. Air Force’s 84th Radar Evaluation Squadron. The simulation included 19 UAS mission profiles and 17 UAS types, said Confesor Santiago, a NASA Ames project engineer.
“In doing all of these activities, this foundational research, we’ve been able to significantly contribute to those two [MOPS] documents,” said Debra Randall, NASA Armstrong chief systems engineer. “Right now, I think both of those documents are 750 pages. They’re full of requirements. There have been numerous simulations, flight tests, data analysis—just a whole lot of work that has contributed to that.”
RTCA may formally release the C2 MOPS document by this fall; minimum standards for DAA were on track for completion this year, said General Atomics project engineer Brandon Suarez, who serves as co-chairman of the DAA working group of SC-228.
The DAA research has involved testing three different software algorithms to warn UAS pilots of midair threats: the General Atomics’ Conflict Prediction and Display System; NASA Langley’s Daidalus (Detect and Avoid Alerting Logic for Unmanned Systems); and the NASA Ames Java Architecture for DAA Modeling and Extensibility, running on the Air Force Research Laboratory’s Vigilant Spirit Control Station.
During the Ikhana flight trials, testers were able to compare the three systems, which simultaneously received flight test data, Suarez said. NASA can also push live flight-test data to various centers and displays through its Live Virtual Constructive-Distributed Environment simulation architecture. The fourth flight series, which called for 15 flights and 270 encounters with NASA, Honeywell and Air Force intruder aircraft, “really focused on trying to provide the final verification and validation flight tests” for the DAA MOPS being developed by SC-228, he said.
General Atomics is participating in the NASA-led research through a formal Space Act agreement. The manufacturer is also advancing its Due Regard radar as a product and capability to enable UAS to fly in unrestricted, civilian airspace.
This spring, General Atomics tested a DAA system including the Due Regard radar aboard a U.S. Customs and Border Protection Guardian UAS—the first such integration and evaluation of the radar on an operational UAS. The tests demonstrated the radar’s “functionality in the national and international airspace operational environment.” Overland testing with the Guardian, a Predator B maritime variant, began at the General Atomics Gray Butte flight operations facility near Palmdale, California, on March 10 and concluded on April 25 over the eastern Pacific Ocean.
“We think it’s a mature subsystem, and we’ve been working with several customers to figure out how to get it on operational platforms,” Suarez said.
The radar also figures in General Atomics’ development of the “Certifiable Predator B,” a new version of the MQ-9 Reaper built to NATO airworthiness standards and equipped to detect and avoid other aircraft. This version will serve as the basis of the UK Royal Air Force’s new Protector platform.
“The Certifiable Predator B has been designed with size, weight and power provisions to install an air-to-air radar, specifically the Due Regard radar,” Suarez said. “It’s also being designed with TCAS II. We’re certainly provisioning for the future detect-and-avoid capabilities that are out there.”
Meanwhile, the next phase of NASA’s UAS Integration in the NAS project will explore new capabilities for unmanned aircraft, including a TCAS II evolution the FAA is advancing called the Airborne Collision Avoidance System X, incorporating new threat logic to prevent midair collisions. An ACAS Xu version is designed specifically for unmanned aircraft. NASA will also look at using alternative sensors, different mid-size UAS and ground-based sense and avoid capability, engineers said.