[Avionics Today 08-11-2015] Research from a June 2015 Boeing
report on the Seattle "Greener Skies" initiative shows that Alaska Airlines' use of NextGen flight procedures at Seattle-Tacoma International Airport (Sea-Tac) can yield massive fuel and emissions savings per landing. The seven-year "Greener Skies Over Seattle" project was launched in 2010 as a collaborative project under the FAA
’s NextGen airspace modernization initiative to add 27 new Performance Based Navigation (PBN) procedures and expand the use of Optimized Profile Descents (OPD).
Alaska Airlines Boeing 737-800. Photo: Alaska Airlines.
The report from Boeing compared the aircraft descent arrival of a typical Alaska Airlines 737-800W using the Required Navigation Performance (RNP) procedure featured for Seattle-Tacoma's runway 16R to the standard earliest approach vector turn, the standard typical approach vector turn, and the standard bad weather approach turn procedure for runway 16R. Results from the comparison showed that the use of the RNP procedure reduces 87 gallons of fuel and 1,858 pounds of carbon emissions compared to the standard approach procedure.
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.
Using the RNP approach also reduces the overall flight time by nearly nine minutes, according to the report. An estimated 80 percent of Alaska's fleet of 137 aircraft are equipped with the avionics required to fly the Greener Skies procedures. Aircraft using large airports such as Sea-Tac are traditionally required to maintain vertical separation of 1,000 feet or three miles of lateral separation until they’re lined up with the runway. As of April of this year, most of Alaska’s fleet has been able to land at the airport with just 1.5 miles of lateral separation, because controllers know that they can rely on the aircraft to stay precisely within their assigned NextGen approach paths.
Oscar Zela, chief technical pilot at Alaska Airlines, told Avionics Magazine that the use of RNP at Seattle and other airports throughout the National Airspace System (NAS) yields “incredible” fuel savings.
"The profile has been built efficiently where — with very few interruptions — the pilot can start the descent at 35,000 feet and end up at around 6,000 feet without too many interim level-offs," said Zela. "Whereas if you were in the conventional profile, the pilot would descend to about 12,000 to 14,000 feet, and then the controller would give you instructions to constantly descend and level off. At Seattle, it would be 10,000, 7,000 5,000 and 3,200 feet and then you get turned in and you just leveled off five times. When you watch the fuel flow meter for an idle plane versus an airplane flying level at 5,000 feet, it is a tremendous difference."
Zela said the airline originally started equipping its aircraft with RNP technology and using the procedures to help with landing at remote and geographically challenging airports within Alaska, prior to the FAA
's official launch of the NextGen program. The FAA and European Aviation Safety Agency (EASA) onboard avionics requirements for RNP operations incorporate multi-mode receivers included in the basic aircraft configuration.
To fly RNP AR 0.30 nm Final and 1.0 nm missed approach, Boeing recommends a dual Flight Management Computer (FMC) configuration and speed and altitude intervention activation as a retrofit for its 737-300/-400/-500 models as well as for its Next-Generation 737s, 757s, 767s, 747-400s, 777s and Boeing MD family aircraft.
Within the next two to three years, Alaska's entire fleet should be equipped to fly RNP procedures at Sea-Tac and throughout the NAS. Alaska estimates that the use of RNP in Seattle is producing savings of $200 per flight.
"We’re going to phase out our Boeing 737-400s and go with all Next Generation (NG) and MAX configuration aircraft shortly," said Zela. "We currently have some regional jets, older Boeing 757s and MDs that aren't equipped, but those will be phased out soon enough. Every pilot at both Alaska and Horizon are trained to fly them, as we want to take advantage of those fuel savings on every flight that we possibly can."
To learn more about the benefits other NextGen procedures and initiatives are producing for airlines throughout the National Airspace System (NAS), check out our upcoming conference, "Avionics for NextGen," here.