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Editor’s Note: UAVs and RNP

By David Jensen | October 1, 2005
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How urgent is the need to find ways to incorporate unmanned air vehicles (UAVs) into the national airspace system (NAS)? Read Holman Jenkins' column in the Aug. 24 issue of the Wall Street Journal, titled dramatically "When Robots Blacken the Skies," and you might think that solutions should have been implemented yesterday.

"A Homeland Security official estimated that his agency would, in a few years, be operating 10,000 unmanned birds to patrol the borders, pipelines, electric grid, etc.," Jenkins writes, adding that once UAV operators enter the civil aviation mix, "the skies could fill with 25,000 UAVs." Jenkins also refers to French and Japanese projects "investigating pilotless cargo and passenger planes."

Don't look for airliner flight decks turning into windowless computer rooms soon. But an onslaught of UAVs in the NAS appears likely. The U.S. military already operates at least 1,500 UAVs, and that number is expected to quadruple by the end of this decade, according to the U.S. Navy League.

The skies truly could become "blackened."

Can all this UAV traffic mingle safely with the manned aircraft traffic, which also is expected to grow? Many at Boeing believe it can. The solution advanced by them and others in the aviation commuinity, including rival Airbus, is a familiar one: required navigation performance (RNP).

"RNP is the only available way to separate aircraft laterally, vertically and longitudinally, even in convective weather...and it can separate vehicles ranging from a UAV with a 3-foot wingspan to the Space Shuttle," says Capt. Thomas Imrich, Boeing Commercial Airplane's chief pilot-research. He gave a presentation of the topic of RNP at a recent Air Line Pilots Association (ALPA) conference in Washington, D.C. "We see RNP as the way airspace will be managed for decades," he adds.

Imrich explains that so long as someone--whether a pilot or a UAV operator--knows an aircraft's trajectory and can assure the aircraft can perform to remain in that trajectory, then air traffic service, which becomes aware of the trajectory via data link, can safely keep traffic separate. "The key factor that air traffic service needs to know is the track," he contends. "It may not even need to know whether the vehicle is manned or unmanned.

"We've just scratched the surface in ways that RNP can be used to solve airspace issues," says Imrich. And while the technology for RNP exists and both Boeing and Airbus have been delivering RNP-capable aircraft for about a decade, the Boeing chief pilot acknowledges that widespread use of the concept remains in the future.

However, the RNP concept did pass a milestone when FAA recently announced it will issue the first RNP approach procedure that the agency has developed and published using public criteria. The approved approach is to runway 19 at Washington's Reagan National airport. Scheduled for publication in September, the new approach brings the decision altitude (DA) for RNP-capable aircraft flying to runway 19 down from 700 feet to, currently, about 450 feet. And once the procedure for a final turn is ironed out, the DA will be reduced to about 260 feet, according to Jeffrey Williams, FAA's program manager for RNAV and RNP.

What makes the approved approach significant is the fact that it used public criteria, which can be applied to the approval of RNP approaches to any runway worldwide. To allow maximum availability to users, it did not use the more capable and stringent criteria for special application such as, for example, Alaska Airlines' RNP approach to Juneau, Alaska.

True, the public criteria for RNP approaches has been too long coming. And, according to one industry source, it represents no more than "baseline" criteria. Nevertheless, the RNP approach into Reagan National--combined with FAA's prediction that a majority of all civil aircraft, commercial and general aviation, will be RNP-capable--indicates the concept's key role in future air navigation. The next steps, therefore, should be to accelerate the approved use of RNP in the NAS while, at the same time, communicate the benefits of required navigation performance to a UAV community that most likely has little knowledge of the concept. Such steps are critical before we witness the anticipated "blackened skies."

Victim of Katrina

Avionics Magazine had planned to feature micro electromechanical systems (MEMS) in our Product Focus section this month. Unfortunately, nature decided differently. Our author, Kathy Kocks, had to evacuate her home in New Orleans in the face of Hurricane Katrina. We plan to reschedule the article for early next year.

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