To many, the notion that unmanned aerial vehicles (UAVs) will one day fly alongside passenger airliners and other aircraft, in fair weather and foul, still seems like science fiction. Yet civil aviation authorities in Europe, North America, Japan, Australia and elsewhere are now finalizing rules under which these operations will take place, possibly as soon as 2010.
In the U.S., the Access 5 consortium, which includes NASA, the Federal Aviation Administration (FAA) and six UAV manufacturers–Aerovironment, Aurora Flight Sciences, Boeing, General Atomics, Lockheed Martin and Northrop Grumman (collectively called the UAV National Industry Team, or UNITE)–aims to achieve approval within five years for routine high-altitude, long-endurance (HALE) flights high above airliners, and anticipates flying alongside them some years beyond that.
Separately but in parallel, the Paris-based UVS-International (UVS-I) has linked a number of non-U.S. national civil and military government and industry UAV interests with similar aims. UVS-I worked last year with a Joint Aviation Authorities/Eurocontrol UAV task force to establish standards for access to civil airspace. The FAA’s Joint Planning and Development Office has also recognized the need to accommodate civil unmanned operations in its next-generation air transportation system plan.
Key requirements identified by both the U.S. and European groups include collision avoidance, fail-safe communication systems, airworthiness, pilot qualifications and training, and emergency procedures. Collision avoidance is the major concern.
While experiments have shown that, with the use of prototype sense-and-avoid equipment, UAVs controlled by ground observers can evade small aircraft at low altitudes, little work appears to have been performed in avoiding medium or large airline aircraft carrying the internationally standardized traffic alert and collision avoidance system (TCAS). TCAS is totally autonomous and impossible to “second guess” by a ground controller, as the tragedy of the DHL/Aeroflot midair collision over Uberlingen demonstrated in April 2002. Fail-safe communications between the UAV and its ground-based pilot are clearly essential, as will that between the pilot and air traffic controllers.
In turn, the JAA/Eurocontrol task force stressed that controllers will not provide special handling for UAVs, which must operate in civil airspace in the same way as manned machines. Similarly, the task force ruled that UAVs must comply with all civil airworthiness requirements, as must those parts of its ground control infrastructure that link the UAV with its pilot.
The qualifications of the UAV’s ground-based pilot remain controversial. Some propose that a civilian private pilot’s license could be adequate for the task. However, others question whether such a minimal standard would be appropriate for operations alongside commercial airliners flown by highly qualified professionals, particularly in bad weather or other demanding circumstances where experienced judgment would be vital.
The U.S. Air Force, with probably more experience in remotely controlled aircraft than any other organization, allows only fully qualified and experienced military pilots to “fly” its UAVs. And emergency procedures are clearly essential, with the need for automatic onboard programming to take the vehicle safely out of the civil air lanes and away from inhabited areas in the event of communications loss, system failures or other control problems.
While regulators have yet to fully resolve these issues, the defining goal centers on achieving a level of safety equivalent to that of manned aircraft throughout the UAV’s flight regime, with particular emphasis on operations in high-density civil traffic zones and around civil airports. For example, a UAV encountering severe wake turbulence or suffering engine failure during a landing approach over a built-up area would have to take corrective action almost immediately.
Consequently, all parties involved agree that safety procedures must be developed and proven for all eventualities before the first unmanned vehicle can enter civil airspace. But the sight of a UAV flying beside our passenger jet does seem to be drawing inexorably closer.