Getting the required navigation performance out of your aircraft

  • 03-Mar-2011 05:19 EST

The magenta lines in this illustration from GE/Naverus show RNP instrument approach paths for Runway 02 at Lijiang, China. The RNP paths provide efficient access from multiple approach corridors to the terrain-challenged Lijiang airport (shown left side of the graphic).

The ability to fly unmanned aircraft in national airspace is a long-term goal of NextGen. In the area of a NextGen benefit that is in effect today, many point to the ability for commercial aircraft to fly precision approaches into airports that are terrain challenged because they are in mountain valleys in places such as Alaska and Peru, for example, or restricted airspace, such as at Reagan National Airport in Washington, D.C.

Performance-based navigation (PBN) lets aircraft fly precisely defined paths without relying on ground-based radio-navigation signals. Required Navigation Performance (RNP) is an advanced form of PBN that can eliminate an average of 10 nmi from the distance an airplane flies on its approach to landing and create significant reductions in annual fuel consumption and CO2 emissions.

Four companies are authorized by the FAA to develop RNP procedures and work with commercial airlines and business operators to implement performance-based navigation: Jeppesen (now owned by Boeing), Naverus (now part of GE Aviation), Honeywell, and Boeing (specifically its Navigation Services group). In many instances, aircraft require special technology such as a head-up display to fly down to the minimums designed in the procedure.

GE Aviation recently introduced a pair of the newest RNP procedures to the world. The RNP paths, designed by Naverus, provide precise lateral and vertical guidance to the runway at Lijiang airport in southern China near the border with Burma.

Sichuan Airlines and Air China first flew the routes late last year when the airport’s instrument landing system (ILS) was out of commission. The ability to fly into the airport without ILS helped maintain commercial air service at the airport during that time.

“Chinese airlines are proving that performance-based navigation solutions, like these RNP flight paths, solve many of today’s most challenging air-traffic-management problems,” said Steve Forte, General Manager of GE’s PBN Services.

The precise lateral and vertical aircraft guidance afforded by RNP and GPS satellite navigation makes it possible for aircraft to land at Lijiang during periods of low visibility or when cloud ceilings are below 1200 ft and there is no ILS.

In addition to the Lijiang RNP flight paths, GE worked recently with Sichuan Airlines to validate RNP paths for its fleet of A319s at Lhasa airport, located in China’s Tibet Autonomous Region. The RNP paths, now in revenue service there, allow Sichuan aircraft to fly in and out of the mountainous terrain in all weather and 24 hours a day. Without RNP, the airport is accessible only during daylight hours and in good weather conditions.

In addition to Lijiang and Lhasa, GE’s PBN Services business has implemented RNP paths at four other Chinese airports—Bangda, Yushu, Linzhi, and Jiuzhaigou—and has designed and deployed RNP paths for two other Chinese airlines: China Southern and China Eastern.

NextGen is a mosaic of technologies that when meshed together will yield significant benefits in myriad areas. While some of these technologies are working as advertised, others are having costly teething problems.

One of those is the $2.1 billion En Route Automation Modernization (ERAM) system, which will replace the 30-year-old technology of the current system. More than 800 computer display workstations at FAA’s Air Route Traffic Control Centers will also be updated under the program. ERAM processes flight radar data, provides communications, and generates display data to air-traffic controllers.

Just before Christmas, Inspector General of the DOT Calvin Scovel issued a report stating that software problems and delays at key sites in the Lockheed Martin-managed ERAM program “will have a cascading effect on other fundamental NextGen programs now and well into the future” and that mitigating those problems are “fundamental to achieving midterm benefits envisioned for NextGen.”

Software-related problems at the initial operating site in Salt Lake City have pushed schedules out almost a year and increased cost estimates by more than $65 million, according to the inspector general. As a result, FAA placed a moratorium on further operational ERAM testing at the key sites to fix the more than 200 problems identified and to develop a new course of action.

“FAA does not believe that ERAM is fundamentally flawed and is working with Lockheed Martin to address the identified problems,” according to the report. “FAA has resumed testing, and senior FAA officials state that system stability is improving, testing is under way at additional sites, and progress is being made in achieving continuous operations without the need to fall back to the legacy system.”

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