A few U.S. companies are developing optionally piloted aircraft in the realization that it could be many years before unmanned planes are smart enough to replicate the ability of a human pilot to sense other air traffic and avoid it, a capability the U.S. Federal Aviation Administration is insisting upon before treating unmanned aircraft like traditional planes.
Aurora Flight Sciences of Manassas, Va., has converted general aviation Diamond DA42 planes into optionally piloted aircraft in hopes of selling them as ISR planes. Mav6, a company founded in 2007 by retired military and intelligence officials, has designed the Air Force’s football-field-length Blue Devil 2 airship to accommodate a pilot when necessary. Northrop Grumman and its Scaled Composites unit in Mojave, Calif., flew their optionally piloted Firebird at the 2011 Empire Challenge intelligence-sharing demonstration in Arizona, albeit in the piloted mode.
Having a pilot aboard would give customers more flexibility to move an aircraft from one site to another to train operators, patrol borders and aid police.
But while experts see niches for these planes, they suggest the aircraft are more a symptom of the problem than a solution to a more fundamental issue facing the U.S. military: what to do about the hundreds of Predator-class unmanned aircraft and the handful of high-flying Global Hawks planes that might be returning to the U.S. as the country pulls forces out of Afghanistan.
The Air Force will need to fly sorties out of U.S. bases to keep those aircraft and their operators sharp.
“We’re going to bring aircraft back from Iraq and Afghanistan, and we’re going to train in the CONUS [continental U.S],” said Steve Pennington, who is the Air Force’s director of ranges, bases and airspace, and executive director of the Defense Department’s FAA policy board. “So the challenge is how to fly in nonsegregated airspace.”
As it stands, the Air Force and FAA agree there should be no restrictions on unmanned aircraft flying at altitudes between 18,000 feet and 60,000 feet, known as Class A airspace. At those altitudes, all aircraft — manned and unmanned — operate under instrument flight rules (IFR), which means the pilot relies primarily on instruments to control the plane within a flight plan filed with FAA. Those instruments can be in the cockpit or, in the case of unmanned aircraft, in a ground control station. Either way, air traffic controllers are responsible for maintaining safe distances between aircraft operating under IFR.
Below 18,000 feet, pilots are permitted to use visual flight rules (VFR), which allow them to look out of the cockpit to navigate and avoid other aircraft. Under VFR, safe separation is the responsibility of the pilot, who has more freedom of movement and does not have to communicate with air traffic controllers, except near controlled airports and some busy areas. There is also controlled IFR traffic below 18,000 feet, but pilots of those aircraft still must look out for uncontrolled VFR traffic. But the military’s unmanned aircraft do not have the ability to “sense and avoid” nearby aircraft, so below 18,000 feet the FAA allows drones to fly only in narrow, segregated flight corridors or in areas for which special permission has been granted.
The Air Force can’t simply install sense-and-avoid equipment on the Predators because the technologies, which include radars, infrared cameras and transponders, are too big or consume too much power. A Predator equipped with sense-and-avoid equipment “can’t carry anything else,” said Dave Bither, Mav6’s vice president for strategic development. “Right now, the technology is a generation away.”
With that in mind, the Air Force is trying to convince FAA that, in the short term, readings from ground radars can be sent to pilots in ground control stations. These radar readings would serve as the core for a ground-based sense-and-avoid system.
FAA has agreed to work with the Defense Department on the ground-based proposal, but it expects the radars to have limited impact on the problem.
“From a practical standpoint, the ground-based sense-avoid is likely to be much more of a localized solution,” said one FAA official who was permitted to speak only on condition of anonymity. “Radar can only reach out so far.”
So, the agency remains largely focused on airborne sense-and-avoid, although “we welcome anything [the Air Force] comes up with,” said Les Smith, flight technologies and procedures division manager for FAA. “At the moment, the biggest technological challenge is sense and avoid,” he said. The Air Force is pushing the radar concept because it wants to avoid creating columns of restricted airspace around UAV bases. Restricting more airspace would disrupt civilian air traffic, and it would amount to a defeat in the service’s effort to normalize operations of unmanned planes.
“The fundamental challenge is either we can segregate more airspace to enable UASs [unmanned aircraft systems] to operate in that segregated airspace with potentially less risk to other users of the airspace,” Pennington said, “or we can integrate and not have more segregated airspace.”
For the next five to 10 years, the Air Force wants to use existing ground-based air traffic control radars and other long-range search radars already in the Air Force inventory, Pennington said.
“We’d repurpose current existing ATC and long-range radars and provide a picture to the crew in the GCS [ground control station] that shows both the cooperative and noncooperative” aircraft, Pennington said, referring to radar icons that display the identity information broadcast by aircraft, and those that are unidentified. “What the ground-based sense and avoid is designed to do is to provide you coverage until you get into Class A airspace or if we’re going to continue transiting below 18,000 feet.”
Around the service’s RQ-4 Global Hawk base in Grand Forks, N.D., for example, the Air Force has created a transition airspace zone, but it would return that airspace to civil users once the ground-based sense-and-avoid system is in place, Pennington said.
The reliance on radars would not require a large leap of faith, Pennington said. It would be relatively easy, he said, to monitor air traffic in narrowly focused corridors in which unmanned aircraft flew predetermined courses.
But that would be a short-term solution. If unmanned planes are to operate with few restrictions, the Air Force will either have to come up with a way to more closely monitor all of the airspace inside the U.S. or find an airborne solution, Pennington said.
“Airborne sense and avoid is the follow-on,” he said.
“The airborne sense-and-avoid solution is certainly going to be much more attractive and preferred,” Smith said. But an airborne solution will be much more difficult to develop and build.
There are two hurdles, Pennington said. With the possible exception of the Global Hawks, the Air Force’s unmanned planes don’t have enough electrical power and volume to accommodate sense-and-avoid equipment. The Navy is taking the lead on sense-and-avoid technology under its Broad Area Maritime Surveillance program, in which Northrop is developing a variant of the Global Hawk for ocean surveillance.
FAA is particularly concerned about the size, weight and power issues, Smith said. The vast majority of unmanned planes are fairly small and fly under 18,000 feet, he said.
The Defense Department has looked at airborne radars and airborne camera systems. But FAA’s Automatic Dependent Surveillance-Broadcast (ADS-B) apparatus — where every aircraft is equipped with a next-generation transponder that would transmit aircraft data such as altitude, velocity and separation — is gaining favor as the basis of a Defense Department airborne sense-and-avoid architecture. This technology is in development under FAA’s Next-Generation Air Transportation System.
“Probably the greater capability over time is going to be the ADS-B,” Pennington said.
FAA is not sold on the ADS-B for airborne sense and avoid for unmanned aircraft, Smith said.
“I would say from the FAA perspective, we’re open to industry to come up with a technical solution to sense and avoid,” he said. “We’re not limiting the technology, but we haven’t endorsed any particular technology.”
The second hurdle as Pennington sees it is that the Air Force and FAA also need to come to an agreement on lost command link procedures.
“Our concern with the command-and-control link is the reliability and integrity of that link itself,” Smith said. “The second part would be predictability of the aircraft when that occurs.”
From the Defense Department perspective, the challenges of a secure control link and lost control link are well understood.
Pennington said unmanned planes actually have an advantage over manned aircraft in some respects. There have been cases of civilian airliners missing their destinations and flying on to different areas, he said. Although pilots of manned aircraft are supposed to be in constant contact and obeying the directions of air traffic controllers, human error or equipment failure can cause an aircraft to lose contact. When that happens, air traffic controllers have no idea what to expect from the aircraft, he said.
But when a pilot in a ground control station loses the command link to an unmanned aircraft, he can contact air traffic controllers and tell them what the aircraft will do. A Predator, for example, is programmed to enter a predictable orbit if the command link is lost.
Moreover, if a pilot becomes incapacitated in a ground control station, another pilot is immediately available to take over, Pennington said.
The next step in development is autonomy, Pennington said. That would enable the aircraft to operate independently if the link is lost or if there is increased satellite communications lag, he said. There are also experiments ongoing with artificial intelligence that would be able to fly the aircraft in the complicated national airspace. In the overwhelming majority of current nongeneral aviation manned aircraft, the flight management system already flies the plane under most circumstances. Pilots have to intervene if something out of the ordinary happens, which is the same as it would be in an unmanned aircraft.
“The only challenge there is: How do I work with my controller friends so that they know what to expect,” Pennington said. The main disagreement is whether the aircraft should maintain a continuous data link with the ATC and give advance notice of its intentions, or if it would operate like a normal aircraft, he said. Additionally, the system would need to be integrated into the FAA’s system.
The companies working on optionally piloted planes have their own challenges with FAA.
“In the developed world, the FAA in the Unites States and similar organizations in Europe and other places, there are no certification specs for an unmanned airship,” said Bither of Mav6.
So Mav6 has made it so the craft can accommodate a pilot.
“Say you’re going from the continental United States to an island in the Caribbean or some place overseas and you want to self-deploy, you would put pilots onboard,” Bither said.
The company has been working with the Air Force and FAA, but Bither said it is apparent that the two agencies didn’t see the approaching demand for operating unmanned planes in civil airspace.
“If you put a pilot onboard, you mitigate that,” he said
Northrop Grumman sees a similar solution in Firebird.
“It offers tremendous flexibility because it is designed as both a manned platform, to fly just as any manned platform would fly in national airspace combined with the persistent multirole capability of an unmanned system when that time comes,” said Rick Crooks, Northrop’s Firebird program director.
Effectively, planes like the Firebird are two aircraft in one, he said. Because a pilot can be sitting in the cockpit monitoring the aircraft’s activities and can see outside and react to air traffic nearby, operators can train and fly in a training area or fly in civil airspace like any other plane, Crooks said.
“The pilot onboard will do the see-and-avoid job that’s required to access congested airspace without special clearance,” he said.
Phil Finnegan, an analyst at the Teal Group consulting firm in Fairfax, Va., said he does not see a large market for the optionally piloted planes. “They are addressing niche requirements, such as for a UAV that can be moved easily despite FAA and other flight restrictions,” he said.
He said he also sees niche applications for militaries or special forces operating in areas that can’t accommodate the launch and recovery equipment required for some unmanned planes. “Although the number of optionally manned aircraft being offered has grown, as yet there have been few buyers of optionally manned aircraft,” he said
Militaries around the world do not have requirements established for these types of aircraft, Finnegan said. “They are not thinking in terms of aircraft that can be used manned or unmanned,” he said. “Procurements are generally written for either manned or unmanned aircraft. Getting that to change requires a change in the way procurements are structured in different countries.”
Although there is little interest in the Defense Department for optionally piloted aircraft, there is one conspicuous exception. The Air Force’s new long-range strike bomber will be optionally manned, the service’s leadership from Chief of Staff Gen. Norton Schwartz and Secretary Michael Donley have oft repeated.
“When it comes to an Air Force bomber, optional manning might offer the advantage of avoiding putting personnel at risk in high-risk operations,” Finnegan said.
This story appeared in the January-February issue of C4ISR Journal.