Fuel and emissions savings from Sea-Tac Greener Skies precision approach initiative exceed expectations
RNP flight display (photo: Alaska Airlines)
Mon 17 Aug 2015 – Reductions in fuel burn and emissions from new navigation procedures used by Alaska Airlines on approaches into Seattle-Tacoma International Airport are about 28% greater than was initially projected, finds a Boeing report. Launched in 2010, the ‘Greener Skies Over Seattle’ initiative is a collaboration under the FAA’s NextGen airspace modernisation programme that involves Performance Based Navigation (PBN) procedures and greater use of Optimised Profile Descents to enhance operational efficiency. By comparing a Boeing 737-800 aircraft descent to the airport using Required Navigation Performance (RNP) procedures with a standard approach turn procedure, each arrival can save 589 gallons of fuel and 1,858 pounds (843kg) in emissions, says Boeing. Meanwhile, Alaska has been recognised for its noise reduction and abatement efforts at Sea-Tac with the airport’s Fly Quiet Bravo Award for 2014.
To design RNP procedures for Sea-Tac, Boeing used specific methodology for modelling environmental performance of aircraft and then model efficient flight trajectories to enhance analysis of flight performance. As well as fuel and emissions savings, the same RNP approach was shown to reduce flight times by 8.8 minutes compared to the typical approach turn and reduce distance travelled by 19 nautical miles. Even greater savings can be made compared to the traditional bad weather vector turn approach procedure, says Boeing. Alaska estimates the new procedure is saving around $200 in fuel per flight.
With Greener Skies, instead of the traditional stair-step descents and a lengthy approach pattern, airlines use satellite technology and a continuous descent to go from cruising altitude to the airport runway along a shorter flight path, at low power and less travel time.
Planes landing on parallel runways at larger airports such as Sea-Tac are normally required to maintain either a 3-mile lateral or 1,000-foot vertical separation on approach until they are lined up with the runway. RNP provides computer-plotted landing paths by using onboard navigation technology and the GPS satellite network, so reducing reliance on ground-based navigational aids. Airlines equipped with the technology are therefore able to land with pinpoint precision in both high and low visibility conditions with just half the lateral separation and thus enabling increased airspace efficiency.
“About 80% of the aircraft landing at Sea-Tac are equipped with avionics to use the Greener Skies approaches and can take advantage of the cost and environmental benefits of flying more efficiently,” said Gary Beck, Alaska’s VP Flight Operations. “What we’ve done here in Seattle is a blueprint for how our industry can help modernise the national airspace for future generations.”
The airline first started equipping its aircraft with RNP technology and using the procedures in the mid-1990s to help land planes in remote and geographically challenging airports in the state of Alaska, and now employs them at 30 US airports. With sister airline Horizon, Alaska is working with the FAA to increase use of similar procedures at Portland International Airport, where typical savings of 45 gallons per flight are being achieved.
As the airline phases out older Boeing 737-400s and other models, Alaska’s entire fleet is expected to be suitably equipped with the onboard technology within two to three years. If all equipped airlines used RNP procedures on all flights approaching from Sea-Tac’s south, it would cut fuel consumption by 2.7 million gallons a year and reduce carbon emissions by 25,600 tonnes, estimates Alaska.
Looking ahead, said Boeing, the Greener Skies initiative will further enhance the efficiency of RNP approaches through the development of refined guidelines and procedures for airlines to follow.
“The NextGen procedures that we’re implementing nationwide and here in the Seattle area are helping to create a better environment while improving safety and efficiency,” said FAA Northwest Mountain Regional Administrator Kathryn Vernon. “By reducing fuel burn, they’re helping to reduce greenhouse gases while providing benefits to everyone who uses the airspace.”
For the fourth year running, Alaska has been presented with a Fly Quiet Bravo Award by the Port of Seattle for its efforts in noise reduction and abatement programmes and for being the quietest airline among the top five carriers at Sea-Tac. Fly Quiet awards were also made to Virgin America and Jazz Aviation (operating as Air Canada Express).
“We applaud our award-winning airline partners for being responsible community members and working to reduce the impacts of noise in and around the airport,” said Mark Reis, Sea-Tac’s Managing Director. “By implementing quieter aircraft, and adhering to flight paths that reduce the impacts of noise, these airlines continue to lead by example and should be applauded for their commitment to being good neighbours.”
