With an eye toward letting drones share the nation's common airspace, the Air Force has set out to find the technology that will let unmanned aircraft sense and avoid other airplanes in flight.
The ability to sense and avoid - common on all manned aircraft that fly the national airspace -- is one of the trickier issues for drones which do not support such technology. It will be a major hurdle to jump as drone vendors and others press for common drone access to national airspace.
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A Government Accountability Office report earlier this year outlined the issue: "To date, no suitable technology has been deployed that would provide UAS with the capability to sense and avoid other aircraft and airborne objects and to comply completely with FAA regulatory requirements of the national airspace. However, research and development efforts by FAA, DOD, NASA, and MITRE, among others, suggests that potential solutions to the sense and avoid obstacle may be available in the near term. The Department of the Army is working on a ground-based sense and avoid system that will detect other airborne objects and allow the pilot to direct the drone to maneuver to a safe location. The Army has successfully tested one such system, but it may not be useable on all types of drones."
Looking to address that particular issue, the Air Force has issued a Request for Information for what it calls "Common Airborne Sense and Avoid Sources" or technology vendors who could build a sense and avoid system for drones.
From the Air Force: "As military (and commercial) employment of Remotely Piloted Aircraft Systems continues to grow, alternatives to the Certificate of Authorization process are being sought in order to decrease coordination requirements and increase mission flexibility. Given the results of Research and Development efforts over the past few years, it is now possible to equip [a drone] with technology that will address some of the major requirements currently driving the FAA authorization process. The USAF is seeking to develop the Common-Airborne Sense and Avoid (C-ABSAA) capability to achieve integrated flight of [drones] in the National Airspace System. The C-ABSAA System must account for both cooperative and non-cooperative aircraft in all classes of air space to include the terminal area. Additionally, the C-ABSAA system must develop a display methodology that will accommodate a wide variety of ground stations. It is anticipated that extensive use of modeling and simulation will be necessary to meet the requirements for Airworthiness and FAA safety certification/operational approval."
Of course sense and avoidance are not the only issues facing drone access to the nation's airspace. The GAO report also noted a few other big items including:
- Ensuring uninterrupted command and control for both small and large unmanned aircraft remains a key obstacle for safe and routine integration into the national airspace. Since unmanned aircraft fly based on pre-programmed flight paths and by commands from a pilot-operated ground control station, the ability to maintain the integrity of command and control signals are critically important to ensure that the drone operates as expected and as intended, the GAO said
- In a "lost link" scenario, the command and control link between the drone and the ground control station is broken because of either environmental or technological issues, which could lead to loss of control of the drone. To address this type of situation, unmanned aircraft generally have pre-programmed maneuvers that may direct the machine to hover or circle in the airspace for a certain period of time to reestablish its radio link. If the link is not reestablished, then the drone will return to "home" or the location from which it was launched, or execute an intentional flight termination at its current location.
- Network security: The jamming of the GPS signal being transmitted to the UAS could also interrupt the command and control of drone operations. In a GPS jamming scenario, the aircraft could potentially lose its ability to determine its location, altitude, and the direction in which it is traveling. Low cost devices that jam GPS signals are prevalent. According to one industry expert, GPS jamming would become a larger problem if GPS is the only method for navigating a drone. This problem can be mitigated by having a second or redundant navigation system onboard the aircraft that is not reliant on GPS, which is the case with larger drones typically operated by DOD and DHS. Encrypting civil GPS signals could make it more difficult to "spoof" or counterfeit a GPS signal that could interfere with the drone navigation. Non-military GPS signals, unlike military GPS signals, are not encrypted and transparency and predictability make them vulnerable to being counterfeited, or spoofed., the GAO report stated.
- Progress has been made in obtaining additional dedicated radio-frequency spectrum for drone operations, but additional dedicated spectrum, including satellite spectrum, is still needed to ensure secure and continuous communications for both small and large drone operations. The lack of protected radio-frequency spectrum for unmanned operations heightens the possibility that a pilot could lose command and control of an aircraft. Unlike manned aircraft-which use dedicated, protected radio frequencies-unmanned aircraft currently use unprotected radio spectrum and, like any other wireless technology, remain vulnerable to unintentional or intentional interference. This remains a key security and safety vulnerability because, in contrast to a manned aircraft in which the pilot has direct physical control of the aircraft, interruption of radio transmissions can sever the drone's only means of control, the GAO said.
The GAO report noted that current domestic uses of drones are limited to activities such as law enforcement, forensic photography, border security, and scientific data collection. According to an industry forecast, the market for unmanned aircraft could be worth $89 billion with the associated research and development for production estimated to be $28.5 billion over the next 10 years.
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