Civilian Drones Have Yet to Pass Weather Test
Researchers at the Army’s White Sands Missile Range in Arizona are developing weather forecasting software to help unmanned aerial vehicles fly in a variety of climates.
Their research would provide important data to government and industry developers of UAVs intended to be flown in U.S. national airspace.
While the use of UAVs as surveillance tools has grown significantly in the military, the domestic market has been slow to take off, mostly as a result of safety concerns and technological shortcomings. Among those concerns is whether UAVs are capable of operating in all weather conditions, researchers said.
Sudden wind changes, icing of camera lenses and restricted flight corridors can interfere with the operation of smaller UAVs, said team leader Terry Jameson.
“If the optical instrument gets condensation on the lens [and] freezes, you can’t see,” he said.
The Federal Aviation Administration so far has severely restricted the use of commercial unmanned aircraft in domestic airspace. But there is a growing list of government programs that are seeking increased use of the technology.
Adm. Thad Allen, commandant of the Coast Guard, recently announced that the service will team with Customs and Border Protection to fly mid-altitude Predator UAVs over the Caribbean and Pacific Ocean. In addition, CBP has begun flying the drones along the northern border.
The National Oceanic and Atmospheric Administration has invested $3 million in a pilot program to use UAVs to monitor hurricanes in the Gulf of Mexico and Atlantic Ocean. Flights to the Arctic and Pacific Oceans are also scheduled for spring 2009, according to NOAA.
NASA has also received a prototype Predator and a Global Hawk — a high-altitude military UAV — to survey forest fires.
Predators and smaller sized UAVs have mostly been used in drier, desert-like conditions in Iraq and along the southern U.S. border. These new applications will test their ability to fly in more volatile atmospheric conditions, White Sands researchers said.
These researchers work primarily with smaller UAVs. Global Hawk is an unlikely candidate for domestic missions. Smaller, lighter planes such as the Aerostar and Predator would fly between 15,000 and 30,000 feet and survey hurricane formations in the Gulf and Atlantic or patrol borders and fisheries.
The smaller the UAVs, the more they are affected by local wind patterns and other weather-related factors, said David Knapp, chief of the atmospheric modeling applications branch at the range.
Navigation systems are also a concern, said David Rockwell, co-author of a Teal Group industry forecast. UAVs generally have only electro-optical sensors — cameras that detect movement on the ground such as illegal immigrants or drug smugglers entering the United States.
“Electro-optical doesn’t see through weather any better than human eyeballs,” he said.
UAVs built for military use often are equipped with synthetic aperture radar (SAR), which can see through cloud formations and weather. Doppler radar is one type of SAR, which civilian UAVs do not have, Rockwell said. The FAA also requires that all commercial airplanes have sense-and-avoid technology to prevent collisions. If UAVs share the airspace with passenger planes, they too will need mechanisms to avoid crashes, said Jameson.
“Sense-and-avoid is critical, but it’s a real struggle to find the technology to do so,” he said.
Testing sense-and-avoid software is also difficult since researchers need to simulate a collision safely, he explained.
Mission duration exacerbates safety concerns. During extended periods, weather conditions may change drastically while the vehicle is on autopilot, said Robert Brown, research meteorologist at White Sands. Previously, aircraft in Iraq were given 24 hours of rest between flights, but because of the increased demand for UAVs, many have remained airborne for 24 hours with only four hours of rest.
Civilian UAVs are subject to restrictions on where they can fly. Even if the FAA loosens the limitations on domestic airspace, Jameson said UAVs will operate on a predetermined flight path. In the event of an emergency, a CBP drone will not be able to land at any airstrip or maneuver too far around threatening thunderstorms.
Also, if a UAV has to deviate too far off course, it may run out of fuel. The Helios — a NASA long-duration flight prototype UAV — crashed in 2003 because of in-flight refueling problems.
“They are flying in a pretty narrow flight corridor,” Jameson said. “They don’t have a choice. They have to get back to the airfield they took off from, even if there is a weather change.”
The smaller UAVs tested by the White Sands group do not have onboard weather sensors. As a result, the team said more effective weather prediction flight mapping technologies are crucial to the expansion of civilian UAV use.
The team is currently developing algorithms that will help them assess fuel requirements by taking into account tailwinds and headwinds, which alter fuel economy.
“When a commercial plane flies it can change altitude freely to make the passengers more comfortable and avoid turbulence,” Knapp said. Small aircraft don’t have as much flexibility.
Currently, Japan is the only country to allow widespread use of national airspace for civilian UAVs, which frequently are employed to spray rice crops, said Steve Zaloga, co-author of the Teal Group study. Legal and financial issues have stalled testing and acquisition of civilian UAVs in the United States, he said.
The FAA “has been saying there will be civilian UAV applications in the next five years,” Zaloga said, “But they’ve been saying that for the last five years. The number of civilian UAVs is only really a handful.”
Tom Cassidy, president of aircraft systems group for General Atomics Aeronautical Systems, which manufactures the Predator and Predator B, said UAV technology is safe enough to be used domestically.
“We feel (UAVs) are ready to be used in civilian airspace, but the FAA is just a little slow,” he said.
Predators, like many commercial airliners, fly at altitudes between 20,000 and 30,000 feet. Electromagnetic currents and special products are used to break ice from UAV wings, Cassidy said. Weather poses no significant threat to civilian UAV use, he added.
Zaloga agreed that weather is not a major obstacle to UAV operations.
“Bottom line, there are some bureaucratic and financial issues that have to be addressed before any civilian UAV programs get off the ground,” Zaloga said.
Rockwell predicted that civilian UAVs will gain a larger presence in U.S. skies as more sophisticated radar systems are installed on smaller unmanned aircraft.
“I’m more optimistic that technological changes will [help] get laws passed,” he said.