Guided entirely by autopilot, an Air China Boeing 757 jet last month snaked along a narrow river valley between towering Himalayan peaks.

Pilots and passengers looked out to mountains left and right as the airplane automatically followed the twists of the valley, descending on a precisely plotted highway in the sky toward a runway still out of sight.

It was the first commercial flight into Linzhi, Tibet, one of the world's most difficult-to-reach airports.

Capt. Chen Dong Cheng, an Air China pilot who rode as an observer on the inaugural flight, said the commercial service into the 9,700-foot-elevation airport wouldn't be feasible without the precise, automated navigation system custom-designed for that particular plane and airfield by Kent-based Naverus.

"We are making impossible things possible," Chen said.

Using global-positioning satellites and on-board instruments, Naverus' navigation technology pinpoints the location of a fast-moving jet to within yards. Chen, in a phone interview, described it as "the future of the aviation navigation industry."

Similar systems could someday be used to dramatically increase traffic flow at run-of-the-mill airports like Seattle-Tacoma International Airport, easing capacity issues that routinely cause passenger delays.

On a conventional approach, a 757 jetliner 6 miles out from the airport needs a path 4 miles wide free of other aircraft and obstacles.

By contrast, the twisting valley into Linzhi is at its narrowest only three-quarters of a mile wide.

On the Sept. 1 flight to Linzhi, known in Tibetan as Nyintri, another observer was Buzz Nelson, retired Boeing test pilot and now technical pilot at Naverus.

As the company's navigation system took control of the 757's descent from 38,000 feet, Nelson said, he could see only clouds below, pierced by the 20,000-foot mountaintops. About 140 miles ahead, nestled in a river valley, the runway wasn't visible.

 

Automatic turn

The plane dropped down on a gentle gradient, and for the last 45 miles to the airport it flew between the peaks, following the turns of the valley.

"You're watching the whole thing unfold. The airplane is turning, going where it's supposed to go. You're looking at the valley; it's all automatic," said Naverus Chief Executive Dan Gerrity.

As the airfield appeared in view ahead, tightly bounded by the meandering river, the autopilot aligned the plane with the center of the runway.

Less than 500 feet from the ground, the pilot took control and landed.

Two months previously, Naverus co-founder and chief technical officer Steve Fulton, a former Alaska Airlines pilot, had flown with Chen on the first test flight into Linzhi, laying the first black rubber tire tracks on the pristine runway.

"I'd never done that before," said Fulton. "Watching the autopilot and flight controls work this airplane in these complex maneuvers was just fantastic. There was nobody in that airplane who wasn't visibly impressed."

In January, Naverus debuted its first system for Air China, at Lhasa, the Tibetan capital. The company has so far invested about $2 million in China, and the two Air China contracts it's completed so far are each worth "six figures, not seven," said Stew Chapin, vice president of marketing.

Though higher than Linzhi, Lhasa airport is at the end of a straight, wide valley that makes landings relatively straightforward. Commercial jets have landed there for 40 years.

The brand-new $92 million airport at Linzhi was a much more severe test.

 

Data collection

Naverus designed the approaches into Linzhi after months of gathering data about the airport, the surrounding terrain, weather conditions, the 757's performance, its flight-deck systems, the airline's training procedures and Chinese aviation regulations.

It charted several approach scenarios, including the track to follow when a jet aborts a landing — and assuming one engine fails in the climb out.

Still, even after exhaustive analysis, simulation and testing, the moment-of-truth first flight is tense, said Nelson.

"Everyone's convinced themselves this is right," he said. "We've gone through all the risk assessments and convinced ourselves things are going to work.

"Then you get in the airplane and take off and you're really happy that they do," Nelson said. "There's a huge relief, that, yeah, it did work."

The Chinese aviation authorities are deploying the Naverus system — a sophisticated version of technology that's broadly known as Required Navigation Performance (RNP) — initially in the west, where the nation's aviation infrastructure is undeveloped and where the terrain limits the usefulness of traditional radio-transmitter ground stations that require line-of-sight contact.

But China is considering applying the same technology to ease congestion in its large coastal cities.

RNP allows controllers to safely reduce separation distances between planes and put them on much more narrowly defined flight paths accommodating many more planes in the same airspace.

"In the old days, you needed airways that were many miles wide, because the airplanes couldn't navigate with accuracy," said test pilot Nelson. "Now, these airways can be very narrow. That's the revolution in technology."

In the U.S., the Federal Aviation Administration (FAA) in July published a "road map" of the planned evolution of RNP "for improving flight efficiency and airport access."

The plan envisages implementing a basic form of RNP approach procedures at 25 of the busiest U.S. airports each year through 2010 and mandating the technology in crowded airspace after 2016.

The FAA is considering a policy change to allow nongovernmental operators like Naverus to provide more sophisticated versions of the technology to airlines.

Packing more planes into airspace could alleviate the circling overhead and long lines of jets queuing to take off that are common at U.S. airports.

"Think of Sea-Tac right now," said Hal Andersen, Naverus co-founder and vice president of flight operations and another former Alaska Airlines pilot. "There's not that many airplanes in the sky."

But would more crowded skies be safe as well as efficient?

Safer than now, asserted Andersen, because the fixing of the aircraft's position is so much more precise and it's equipped with multiple redundant systems.

Airlines are sold on the technology by its efficiency, he said, but pilots want it because it's safer.

"This has an order-of-magnitude better level of safety ... than the traditional approaches," Andersen said. "That is ... the way a lot of pilots are attracted to it."

 

Dominic Gates: 206-464-2963 or dgates@seattletimes.com