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UAVs Are Likely to Affect Our National Airspace System

February 2005

illustration of uavs being used in various civil situations

As use of unmanned aerial vehicles (UAVs) continues to grow, they will become a significant component of military, civil, and commercial aviation. What is not clear yet is how UAVs in U.S. skies will affect the evolution of our National Airspace System (NAS), which is a web of communication, navigation, and surveillance systems that ensure safe flight. MITRE's Matthew DeGarmo and Gregory Nelson describe how UAV operations could impact the NAS in an article entitled, "Prospective Unmanned Aerial Vehicle Operations in the Future National Airspace System," published by the American Institute of Aeronautics and Astronautics. DeGarmo is a senior systems engineer and Nelson is a lead economic business analyst at MITRE's Center for Advanced Aviation Development (CAASD) in McLean, Virginia.

Military investment in UAVs is currently increasing, say DeGarmo and Nelson. Potential uses in civil operations, particularly for homeland security, are also being investigated by federal, state, and local governments. The vehicles offer a unique range of features, most notably ultra long-endurance and the capability to take on high-risk missions that cannot reasonably be performed by manned aircraft. (For example, scientists used a government UAV to gather data over Mount St. Helens recently when it was dangerous for people to get too close.) "Advances in automation and sensor technologies, plus the potential for costs savings, are fueling the demand for UAVs," says Nelson.

How might UAVs be used in 2020? DeGarmo and Nelson give seven scenarios that represent a broad cross-section of proposed UAV applications:

Stratospheric Telecommunications Airship
High-Altitude Imagery
Border Patrol
Maritime Surveillance
Environmental Sensing
Media and Traffic Reporting
Tactical Law Enforcement

Going into Civil Airspace

Current trends indicate that a viable civil and commercial market for UAVs will likely emerge within the next 15 years, if not sooner. Already, a NASA-sponsored industry and government effort known as Access 5 plans to transition high-altitude UAVs into civil airspace within the next five years. In anticipation of increased use, the Federal Aviation Administration and other organizations will be working to develop and codify standards, procedures, and regulations specific to UAVs.

High-Altitude
Imagery

Here's a scenario (created by DeGarmo and Nelson) for how a UAV might be used to take aerial images for a land-use survey in the year 2020. The operation begins with the filing of a 4-D flight plan with the air traffic control system for a 36-hour mission. The planned flight indicates a large sweeping pattern at 50,000 feet. The route covers rural, urban, and coastal areas and the UAV will average 150 knots airspeed (optimal speed for the sensors). The vehicle is based at a tower-controlled airport but is being operated and monitored from a secured office located remotely from the airport.

The airport tower gives the UAV operator permission to taxi. Taxi operations are normally performed autonomously but due to traffic and construction at the airport, the vehicle is manually taxied using a forward-looking video camera. After takeoff, the UAV ascends autonomously in accordance with a 4-D departure procedure. The ground pilot monitors flight progress and conducts system safety checks during ascent. At 30,000 feet, the air traffic control system detects a potential traffic separation conflict and automatically sends instructions to the ground pilot for the UAV to level off for traffic separation. These instructions are electronically acknowledged by the ground pilot and transmitted to the UAV. A short time later the vehicle resumes climbing to its cruise altitude of 50,000 feet. Because weather and traffic are not significant at that altitude, the flight is conducted in accordance with the originally filed 4-D flight plan. After completing its mission, the aircraft returns uneventfully to the originating airport.

What's the impact on the NAS? Due to the high altitude of the operation, the predictable 4-D nature of the flight, and the full suite of navigation and communication equipment onboard the UAV, in this scenario there is very little impact on the system. The slow climb rate and speed of the vehicle does create some air traffic control challenges, but these are manageable.

"We expect future UAV operations to pose a unique set of issues for air traffic management," says DeGarmo. "First, because UAV designs and capabilities will vary widely, their performance characteristics will differ significantly from those of manned aircraft. UAVs will range in size from several ounces to thousands of pounds. Many will fly slowly and lack maneuverability relative to their manned counterparts."

UAVs will be launched and recovered from a wide variety of locations, including ships, tops of buildings, and runways. UAV communication systems, too, will show great variety, from those capable of global reach to those limited to line of sight. Sophistication will vary among vehicles: some will have fully autonomous flight control, some will require more direct pilot inputs.

"The types of future missions being planned for UAVs won't be point-to-point but will typically involve some form of patterned flight or tracking activity that may include intermittent short- or long-term orbits," says DeGarmo. And UAV endurance will last from hours to months, depending on the vehicle and mission.

All these variations have the potential to significantly affect air traffic operations. However, through research and planning, the air traffic management system of the future will be well equipped to manage the additional complexity related to the rise of UAVs.

National Airspace System Will Change

The NAS, say DeGarmo and Nelson, is expected to change significantly over the next 16 years, with the introduction of new technologies and procedures to address such issues as capacity constraints and inefficiencies in the existing system. The addition of UAVs, with their wide range of physical and performance characteristics—unlike any current aircraft—will place additional challenges on the air traffic management system.

However, many of the new paradigms already being considered for the future NAS will likely facilitate the routine and safe entry of UAV operations into civil airspace. "For example," says Nelson, "a next-generation information management system will allow all users of the NAS to know the location and intent of all other aircraft (both manned and unmanned) in their area."

The NAS will also enable the functioning of autonomous systems embedded in UAVs and other advanced, data-dependent aircraft of the future. This 4-D (3-D plus time) navigation and control will allow properly equipped UAVs to file 4-D flight plans through the air traffic system and integrate seamlessly into the NAS.

In comparing prospective UAV applications with assumptions of a future NAS, DeGarmo and Nelson believe that the NAS can accommodate UAV growth. This will, however, require an effective strategy—a national roadmap—that accounts for the interactive complexities and unique properties of UAVs. "More research is needed to assess the potential influence of UAVs on future traffic flows, airspace capacity, infrastructure, and air traffic control procedures," says DeGarmo. This research will assist policy makers, manufacturers, air traffic control service providers, and regulators in building a future environment that supports all users of the NAS and facilitates the advancement of aviation.

Next Steps

DeGarmo has recently started working on a MITRE-sponsored research initiative that involves evaluating and visualizing UAV operational concepts and also examining potential impacts of various UAV operations on local, regional, and NAS-wide operations. Using MITRE's and CAASD's unique lab resources, DeGarmo will be able to provide both quantitative and qualitative measures. In addition, DeGarmo's research team is exploring collaborative opportunities with NASA and others to coordinate analyses, validate findings, and share lab resources.

—by David Van Cleave

Related Information

Technical Papers and Presentations

Prospective Unmanned Aerial Vehicle Operations in the Future National Airspace System [PDF, 27KB]

Page last updated: February 23, 2005 | Top of page

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