As air taxis, drones and other innovative aircraft enter U.S. airspace, systems that communicate an aircraft’s location will be critical to ensuring air safety.
The Federal Aviation Administration (FAA) requires aircraft to communicate their locations to other aircraft and air traffic control in real time using a Automatic Broadcast Surveillance System (ADS-B). NASA is currently evaluating the ability of an ADS-B system to prevent collisions in a simulated urban environment. Using NASA Pilatus PC-12 Aircraft researchers are studying how these systems could handle the demands of low-flying air taxis through cities.
When operating in urban areas, a particular challenge for ADS-B systems is consistent signal coverage. Like cell phone signal loss, air taxis flying through densely populated areas may have difficulty maintaining ADS-B signals due to distance or interference. If this happens, these vehicles become less visible to air traffic control and other aircraft in the area, increasing the likelihood of collisions.
To simulate urban flight zone conditions and better understand signal loss patterns, NASA researchers established a test area at NASA’s Armstrong Flight Research Center in Edwards, TX. California, September 23 and 24, 2024.
Flying in the agency’s Pilatus PC-12 in a grid pattern over four ADS-B stations, researchers collected signal coverage data from multiple ground locations and equipment configurations. The researchers were able to determine where signal dropouts were occurring from strategically placed ground stations in relation to the aircraft’s altitude and distance from the stations. This data will inform future placement of additional ground stations to improve signal enhancement coverage.
“Like all antennas, those used for ADS-B signal reception do not have a consistent pattern,” said Brad Snelling, lead engineer of the vehicle test team for NASA. AIR MOBILITY FINDERS project. “There are certain areas where terrain will block ADS-B signals and depending on the type of antenna characteristics and location, there are also flight elevation angles where reception may cause signal dropouts “Snelling said. “This would mean we need to place additional ground stations in several locations to increase the signal for future test flights. We can use the test results to help us configure equipment to reduce signal loss when we conduct future flight tests. »
The September flights at NASA Armstrong built on previous tests of ADS-B in different environments. In June, researchers at NASA’s Glenn Research Center in Cleveland flew the Pilatus PC-12 and found a consistent ADS-B signal between aircraft and communications antennas mounted on the roof of the roof of the center Aerospace Communication Facility. Data from these flights helped researchers plan NASA’s recent Armstrong tests. In December 2020, test flights conducted under NASA’s Advanced Air Mobility National Campaign used a Kiowa OH-58C helicopter and ADS-B ground stations at NASA Armstrong to collect basic signal information.
NASA’s research into ADS-B signals and other communications, navigation and surveillance systems will help revolutionize American air transportation. Air mobility researchers will evaluate data from the three separate flight tests to understand the different transmission conditions and transmission equipment needed for air taxis and drones to operate safely in the national airspace. NASA will use the results of this research to design infrastructure to support future research, navigation, and surveillance research of airborne communications, new ADS-B-like concepts for unrealized aircraft systems.