Despite growing demand for unmanned aircraft, technological and regulatory obstacles may keep them from routinely sharing US skies with piloted aircraft before 2020, a government watchdog said Friday.
In a new report, the Government Accountability Office said the US military's experience in Iraq and Afghanistan is generating both trained operators and an industrial base to support the expanded domestic use of unmanned aircraft.
Local authorities want to use them to spot fires or keep watch over crime scenes, and commercial interest has grown as well, according to the report.
But significant technological and regulatory challenges still stand in the way of safely mixing unmanned aircraft with piloted aircraft, it said.
"No technology has been identified as a suitable substitute for a person on board the aircraft in seeing and avoiding other aircraft," the report said.
Their communications and control links are vulnerable to intentional or unintentional interference that could cause a crash, and ground control stations may need to be protected against hostile takeovers.
Reliability of components in unmanned aircraft systems (UAS) is another problem, according to the report.
"Our analysis of four and a half years of DOD's (Department of Defense) data indicates that UAS component failures caused about 65 percent of the accidents and human factors issues -- a common challenge in new technology -- caused about 17 percent of the accidents," it said.
Unmanned aircraft are currently limited in the United States to border patrol operations and scientific data gathering with special case-by-case approval by the Federal Aviation Administration.
The report said various federal agencies are taking steps to deal with the barriers to wider use of unmanned aircraft for domestic missions.
The FAA, for instance, is sponsoring research on technologies that deal with the "detect, sense and avoid" issues, and is trying to obtain dedicated radio frequency spectrum for unmanned aircraft operations, the report said.
A federal advisory board is developing technical standards of unmanned aircraft.
But the report said: "Fully addressing regulatory challenges to allowing all UASs to have routine access to national airspace may not occur until 2020."
The impact of unmanned aircraft on the national airspace system remains speculative, but studies have warned they could be disruptive, the report said.
UASs pose unique challenges because, unlike manned aircraft, they often hover or circle in one location and have speed, maneuverability and climb rates that may differ from manned aircraft.
"These differences could affect air traffic flow, air traffic controller workload, and departure and arrival procedures," the report said.
They also would likely add to the volume of air traffic, it said.
On the other hand, they might be quieter and produce less emissions than manned aircraft performing the same tasks, the report said.