It’s time for another post in my series talking about the benefits of NextGen air traffic control. Last time, we were in New York, but this time we’re heading across the country to Seattle where Alaska Airlines has been spearheading some major efforts to shorten flight times and reduce fuel burn thanks to new approaches in Seattle. I spoke with Sarah Dalton, Director of Airspace and Technology for Alaska along with Oscar Vela, a First Officer at Alaska who has been working on this project, to learn 
more.
The project is being called Greener Skies over Seattle, and I was first told about it when I visited the airline last September. The idea is to use RNP to enable a much quicker path into the airport. The picture on the right is a great one to show how this works for approaches from the South.
Today, aircraft coming from the south descend into Seattle using a traditional step-down descent. That means that airplanes are cleared to descend to certain altitudes. When they get there, they spool the engines up and level out until they are cleared to the next level below. Though this works well in practice, it is a waste of fuel since it requires constant increasing of thrust and then decreasing it again. There is now a new descent profile which will allow aircraft to come down smoothly and without interruption all the way down to 6,000 feet.
Once the aircraft gets to 6,000 feet, it is going to be about where the yellow and blue lines meet on the left side of the image (at least using this particular approach). It’s across the water from Sea-Tac Airport. Today, aircraft mostly have to continue on the blue line and then make a turn further up north before coming back around. The entire process is choreographed by the air traffic controllers with specific instructions on altitude and heading until the airplane is lined up with the runway. When the visibility is bad (which I assume is every single freakin’ day in Seattle), the aircraft will then use an ILS approach to come straight in for landing.
For those airlines that have RNP-equipped aircraft and trained crews, air traffic control now has the ability to give them an RNP approach. Instead of going further north, aircraft would engage at 6,000 feet and would automatically be guided around the curve and lined up for landing. This not only cuts off flight time and saves fuel, but it keeps a large swath of populated land north of the airport without airplane noise.
This sounds great, but why is NextGen necessary for this to work? Well, it’s the accuracy of the computer navigation that allows this to happen. Seattle has three parallel runways and often is landing on two runways at once. The FAA has a rule today in Seattle that if an airplane is coming into a turn on approach into the airport, there has to be at least 1,000 feet vertical or 3 miles horizontal separation. They can’t make that work so close to the airport so they have to send airplanes further north to get them lined up with cutting capacity at the airport.
The FAA and air traffic control are now trying out this new procedure, which began flight testing in June. It’s a big change for those who are used to controlling traffic, because they have to let go of some of that control. How are the tests going so far? Quite well. There have been 1,300 flights operated by Alaska under the test so far and there’s hope that this will be in place as a real procedure by spring of next year.
I asked if they had learned anything from the trials that required tweaking yet, and there was one thing. Since this is a much more precise approach, managing the speed on the airplane becomes much more important. So that’s something they need to make sure is hammered home with the pilots.
One of the criticisms brought up when I wrote about JetBlue at JFK in the last piece in this series was that some said it would rarely matter because runways weren’t usually in those configurations. That is not the case here.
The approach I mentioned is just one of the ones being tested. There are approaches that use this technology for landings to the north and to the south. It is used for traffic coming from the west, north, or south as well. The only traffic that can’t benefit from these approaches is that coming from the east. For Alaska, that means 75 percent of its traffic (and around 60 percent of Horizon’s traffic) can take advantage of this, and Alaska accounts for a huge chunk at the airport. All of the airplanes are equipped and the pilots are trained in those fleets, so there is significant benefit right off the bat.
But others with RNP capability can use this as well. It’s just one example of how landing procedures can be rethought with more accurate navigation. The result is less noise, less fuel burn, and shorter flight times.
