The US Air Force (USAF) is planning to award contracts in mid-September for research into automated ground-handling and approach and departure manoeuvre systems for UAVs operating from air bases that are simultaneously handling manned ircraft.

The research project – designated automatic terminal area operational (ATAO) control – is intended to explore all aspects of UAV ground movement, including taxi, obstacle avoidance, area movement command and control, communications, standard and non-standard departures, published approaches, and holding and overhead patterns.

The project will also look at the inter-relationship between UAV ATAO requirements and sense and avoid systems to prevent mid-air collisions.

A broad agency announcement for the project closed on 11 August, with initial funding award expected to total around $500,000 to cover work to the end of 2008.

Solicitation documents describe shared airfield terminal areas as “an especially congested are of operation for aircraft, an atmosphere that is time-critical, detail sensitive and conducive to task saturation”.

They add: “UAVs encounter unique problems in the terminal area. A UAV operator has difficulty maintaining the same situational awareness and tempo of activities as an airborne pilot.”

Current integration arrangements are largely based on UAVs flying in “sterile” or segregated airspace corridors. The ATAO solicitation says that while this provides more flexibility for UAV operators, it is an approach that is increasingly under pressure in real world operational conditions.

“Most long-term planning scenarios now involve heavy UAV participation in the battlespace. For UAVs to be fully incorporated into the air war, they must be able to be integrated seamlessly into operations with manned aircraft. To be able to reach this operational goal of the ‘same base, same time, same tempo’ as manned aircraft, development and application of autonomous control technology will be necessary.”

The AFRL project is based on the assumption that the UAV must “appear to act as a manned aircraft” at all times in the terminal area. “It is necessary to replace some pilot capabilities with new autonomous capabilities inherent in the UAV operating system. Path generation and deconfliction is required. The UAV must be capable of foreseeing a possible collision, airborne as well as on the ground, and generating a safe course to avoid it.”

Automated ground manoeuvring of UAVs will necessitate development of situational awareness systems that allow the aircraft to understand “where it is on the airfield at all times. Taxiing in the terminal area, following taxi lines, understanding hold short points, runway centreline, and knowing the layout of parking areas is essential for an autonomous system to navigate on an airfield. The ground sense and avoid problem in many cases can be simplified to sense and stop, taxi right of way and deconfliction. However, ground operations may complicate the sense and avoid problem with the introduction of obstacles [and] hazards other than aircraft such as people, animals, vehicles and equipment.”

Any ATAO system must also be able to understand the ground movements of other aircraft, and adapt to “changes in instructions or routes directed and quickly respond to those instructions. To accomplish this while operating at the same tempo as manned aircraft, UAVs must be able to communicate at the same tempo as manned aircraft and follow air traffic control directed commands autonomously. For this, voice recognition and synthesis may be necessary, especially where a UAV formation might be split up and on different frequencies.”

Existing ground manoeuvre systems for the bulk of production UAVs are based on a pilot-observer remotely operating the aircraft too and from runway areas and adjusting the aircraft movements in response to radio traffic from the control tower. A limited number of systems, including the Northrop Grumman RQ-4, use GPS-based navigation to support automated ground manoeuvre with ground control station crews providing system overrides in response to guidance from tower controllers.

Source: Flight International