[KSEA]: One Way FAA can Use NextGen to Optimize Noise Mitigation

Here’s a tip for how to very effectively expose FAA’s NextGen failure: study how ATC handles arriving flights during low-traffic time periods. For example, at the SeaTac Airport [KSEA], where Delta’s decision to start up a new hub in 2012 is causing substantial growth in annual airport operations, the arrivals stay busy through most of the day, but there are a few hours each night when you can find only one arrival being worked. So, the question is, what is the shortest arrival routing ATC will issue when working a single, all-alone arrival, and how does that arrival route change with the addition of more arrivals?

When you study the empirical flight data, you quickly find the answers, and they consistently show: FAA’s largest impediment to system efficiency is simply TOO MANY FLIGHTS. In other words, if FAA really cared to optimize safety and efficiency, they would focus on managing capacity, keeping operations per hour below thresholds that precipitate delays and congestion.

Consider a Recent Arrival: United 505 from Denver

One example of this was United 505, which arrived after 2AM on Tuesday, December 20th. First, notice the overall flight on the satellite view below: as has been the case for many decades, they flew a straight line from Denver, with no zig-zags. Notice, too, that the only significant distances were added at Denver and at Seattle, as needed to accomplish transition to and from the enroute portion of the flight.

How Can FAA Better Use the NextGen Technologies?


(VFR sectional with a red curve added, depicting an optimized noise mitigation approach over Puget Sound and Elliott Bay. Crossing altitudes at 8000ft and 3000ft are added, red text on green background.)

The residents of Seattle are lucky to have a large water body that aligns well with their main commercial airport. But, the basic design elements needed to optimize noise mitigation were not fully considered when FAA was selling NextGen. Key design elements should have included:

  1. keep the arrivals high as long as possible. (way back in the 1970s, FAA actually had a noise mitigation program called ‘Keep em High’!)
  2. for the final ten miles, set up each arrival for a continuous rate of descent, optimally at around 300-ft per mile flown. (thus, arrivals should be designed to cross a fix at roughly ten-miles from the runway end, and 3,000ft above airport elevation)
  3. for the distance from 20-miles to 10-miles from the runway end, design a higher rate of descent, perhaps 500-ft per mile flown. (thus, arrivals would descend from 8,000ft above airport elevation to 3,000ft above airport elevation, during this 10-mile portion of the arrival; with this design, commonly used flight automation systems would enable pilots to easily comply with the designed optimized descent profile and route)
  4. plan to have ATC accomplish sequencing, spacing and speed management to the point where the final 20-miles of the approach begins. (in this case, roughly mid-channel over the Vashon ferry route, at an altitude nominally 8,000 feet MSL)

Interestingly, this proposal is quite similar to one of the approaches that FAA designed and implemented, the RNAV (RNP) Z Runway 16R Approach:ksea-20161204cpy-rnav-rnp-z-rwy16r-ifr-plate
For years, in an extended and heavily-coordinated pitch to sell the NextGen program in Seattle, FAA and others pushed the idea that all arrivals from the west side (from California, Oregon, Hawaii, coastal BC & Alaska) would be routed inbound over Elliott Bay during the predominant south flow landings at SeaTac. This was a good idea, but FAA did not go far enough. I.e., when FAA designed this approach procedure, they focused solely on the portion from the middle of Elliott Bay to the runway; they should have also focused on how each flight would get to that point in Elliott Bay (look for ‘SEGAW’ in the plate above). A truly optimized approach would define fixes and precise altitudes, starting between the fix VASHN (on the approach plate above) and the Fauntleroy ferry dock; such an optimized approach would route each arrival over-water and eventually over the vicinity of the stadiums, and would include speed and altitude profiles easily achieved by today’s air carrier fleet. Note that the profile view for the current deficient approach procedure (above) starts at fix WOTIK, which is at a 6-mile final and well south of Spokane Street.