West-side approach to Sea-Tac, showing typical flight path (blue) and RNP flight path (green). Source: Alaska Airlines. Click to enlarge.

Alaska Airlines demonstrated next-generation flight procedures this week during a test flight over Puget Sound that burned less fuel and reduced emissions by 35% compared to a conventional landing. The flight was part of Alaska Air Group’s “Greener Skies” project at Seattle-Tacoma International Airport (Sea-Tac) focused on using satellite-based guidance technology pioneered by Alaska Airlines to fly more efficient landing procedures that will reduce environmental impacts in the Puget Sound region.

The test flight used satellite guidance technology called Required Navigation Performance (RNP) to fly more direct, continuous descent approaches. Alaska Airlines estimates the new procedures at Sea-Tac will cut fuel consumption by 2.1 million gallons annually and reduce carbon emissions by 22,000 metric tons. They will also reduce overflight noise for an estimated 750,000 people living below the affected flight corridor.

Performance-Based Navigation
Performance-based Navigation (PBN) is the specification by aviation authorities of the capabilities and requirements necessary to operate in a given airspace, or the use of a given procedure, instead of specifying required technologies or specific avionics.
RNAV (Area Navigation) is achieved through a combined use of aircraft navigation accuracy, route separation and/or air traffic control intervention.
RNP is RNAV operations with on-board navigation containment, monitoring and alerting.
—FAA RNAV and RNP Group

The airline, in cooperation with the Port of Seattle, Boeing and other airlines serving Sea-Tac, is seeking Federal Aviation Administration (FAA) approval for the procedures, which could ultimately be used by all properly equipped carriers at Sea-Tac.

Testing for the project began last summer and, since then, Alaska Airlines has flown two other demonstration flights and submitted more than half of the proposed procedures for FAA review. Representatives from Alaska, Boeing, the FAA and the Port of Seattle participated in the most recent demonstration to observe the level of flight path precision and fuel consumption on eight landing approaches in a Boeing 737-700.

With a landing weight similar to a typical passenger flight, the shorter and more efficient approaches reduced carbon emissions and saved 400 pounds of fuel per approach.

Sea-Tac is the ideal location to pursue this cutting-edge project. Seattle has the highest percentage of advanced RNP-equipped planes in the nation, and—working with the FAA—Alaska Airlines, Boeing and the Port of Seattle are committed to making ‘Greener Skies’ a reality as soon as possible. Ultimately this project could serve as a blueprint for next-generation aviation technology throughout the country.

—Ben Minicucci, Alaska’s chief operating officer

Typically, commercial aircraft follow a lengthy approach pattern and series of stair-step descents before landing. Using RNP technology and a continuous descent, also called an optimized profile descent (OPD), aircraft can descend from cruise altitude to an airport runway along a shorter, more direct flight path at low power.



Conventional approach.   Optimized Profile Descent. Click to enlarge.

Planning and testing of the procedures will continue through the remainder of the year and will be integrated into Alaska Airlines and sister carrier Horizon Air’s commercial operations at Sea-Tac pending FAA approval.


Alaska Airlines RNP display. Source: Alaska Airlines. Click to enlarge.

Alaska Airlines pioneered RNP precision flight-guidance technology during the mid-1990s to help its planes land at remote and geographically challenging airports in the state of Alaska. RNP provides computer-plotted landing paths by using a combination of onboard navigation technology and the global positioning system (GPS) satellite network. It improves safety and reliability in all weather, and reduces reliance on ground-based navigation aids. Alaska Airlines currently uses FAA-approved RNP procedures at 23 US airports.

Alaska Airlines is the only major US air carrier with a completely RNP-equipped fleet and fully trained crews. Alaska is also the first airline approved by the FAA to conduct its own RNP flight validation. Horizon Air’s fleet will be fully RNP-equipped by the end of 2011.

RNP and OPD are part of the Next Generation Air Transportation System, the FAA’s plan to modernize the National Airspace System through 2025. This initiative will increase airspace capacity and efficiency while improving safety and reducing environmental impacts through the replacement of legacy ground-based equipment with new satellite-based technology and aircraft navigation capabilities.

As part of the initial Alaska Airlines RNP operational approval team, Boeing began installing RNP guidance technology on its aircraft in 1994. Currently, all Boeing production airplanes are RNP-capable, and solutions are available to upgrade the in-service fleet.

Boeing RNP functionality includes flight crew interface through a flight management control display unit (CDU) and the airplane crew alerting system. Navigation, flight planning, and alerting algorithms are contained in the airplane flight management function.