- The more accurate navigation, along with other NextGen procedures, have reduced fuel burn by 1.8 million gallons — saving air carriers $5.3 million — and decreased carbon emissions by 15.7 thousand metric tons, according to FAA analysis.
- Arrivals are now three times more likely to execute continuous descents beginning at about 13 nautical miles (nm) and 2 minutes closer to IAH and HOU.
- Arrivals from San Antonio are the biggest beneficiaries of improvements with average distance and time savings of 3 nm and 41 seconds, a nearly fourfold increase in the proportion of flights executing OPDs, and a more than 1,000 foot increase in altitude of level segments.
Airports referenced in this story
- Performance Based Navigation (PBN)
- Addresses ways to leverage emerging technologies, such as satellite-based Area Navigation and Required Navigation Performance, to improve access and flexibility for point-to-point operations.
NextGen Priorities Focus Area
In May 2014, the FAA redesigned the airspace and added new satellite-based procedures to bring new efficiencies to the skies above southeast Texas. This includes George Bush Intercontinental Airport (IAH) and Houston Hobby (HOU) airports, as well as 16 satellite airports. They are all part of the Houston Metroplex, a major metropolitan area where several airports are located close to one another in congested airspace. One year later, the airspace improvements are delivering millions of dollars in estimated annual benefits to operators at the two largest airports in the Houston area — based on an analysis by the FAA's Houston Metroplex Post-Implementation team.
Among the changes, the FAA introduced additional Performance Based Navigation (PBN) procedures, which offer pilots the ability to navigate with greater precision and accuracy through the use of satellite navigation technology and onboard equipment.
The more accurate navigation, along with other NextGen procedures, have reduced fuel burn by 1.8 million gallons — saving air carriers $5.3 million — and decreased carbon emissions by 15.7 thousand metric tons, according to FAA analysis.
Before the metroplex redesign, arrival pathways quickly became crowded as demand increased during the day, creating choke points. The FAA changed the entry points to enable increased use of dual arrival streams from the northeast and northwest. These PBN pathways provide additional access points into terminal airspace, and are arranged to keep arrivals for one airport clear of the arrivals to another, while also avoiding departure routes.
Another change lets aircraft stay in the high altitude overhead stream longer while giving them a specific time to land at an airport. Pilots are now reducing engine power to near idle at the beginning of their descent into the Houston area — from cruising altitude until established on the final approach to the runway — using an Optimized Profile Descent (OPD).
Satellite navigation makes it possible for pilots to begin their descents from a much higher altitude — 38,000 feet — as aircraft glide toward the runway. These procedures replace the less efficient stair-step approach where aircraft level out between drops in altitude, all the while increasing and decreasing the throttle. OPDs also enable continuous descents within a flow, resulting in a larger proportion of arrivals performing more efficient descents. As a result, overall flight efficiency is increased.
"Controllers can spend more time monitoring aircraft instead of constantly issuing different headings, altitudes and speeds to pilots," said Ron Renk, United Airlines chief technical pilot for navigation issues. In addition to the benefits to controllers and pilots, OPDs save airlines millions in fuel costs.
Trade-offs in airborne flight efficiency were observed for both arrivals and departures. Distance flown for IAH and HOU arrivals and departures increased by less than 1 percent, but these small lateral inefficiencies were offset by vertical improvements, particularly for arrivals. Arrivals are now three times more likely to execute continuous descents beginning at about 13 nautical miles (nm) and 2 minutes closer to IAH and HOU. Longer cruise and shorter descent phases of flight mean longer time and distance spent at higher, more fuel-efficient altitudes, and consequently more efficient flight profiles.
Arrivals from San Antonio are the biggest beneficiaries of improvements with average distance and time savings of 3 nm and 41 seconds, a nearly fourfold increase in the proportion of flights executing OPDs, and a more than 1,000 foot increase in altitude of level segments.
"This particular metroplex set the bar pretty high for the rest of the country," said Jim D'Ambrosio, air traffic manager at Houston Center. "The people in Houston were able to implement all four corner-posts at the same time. There were over 68 changes in fix postings and procedures. All this happened with the flip of a switch at midnight on May 29, 2014. Today, we see the use of OPDs, we are using Time Based Flow Management (TBFM) and shortly, adding in the extended metering Ground Based Interval Management System (GIM-S)."
Controllers use TBFM to manage aircraft speeds at higher altitudes prior to the start of descent to ensure appropriate spacing. This allows aircraft to remain on the efficient OPD procedures with minimal vectoring, while still ensuring an efficient feed. The goal is to establish the time at which the aircraft should arrive on the runway. The FAA is continuing to adjust TBFM settings to improve use and efficiency.
As TBFM capabilities are expanded in Houston, GIM-S automation will provide speed advisories to en route controllers to help deliver aircraft to meter points in accordance with the arrival flow schedule. GIM-S capabilities increase opportunities for aircraft to fly OPDs.
Metroplex programs are a top priority of the FAA and the aviation industry. They are among the commitments agreed upon in the NextGen Priorities October 2015 Joint Implementation Plan. Future modernization efforts will add departure points, expedite departures, add new high-altitude PBN routes, and realign airspace to support those changes.
"There are still improvements to make to fine tune the procedures" said D'Ambrosio.
As the Houston air traffic facilities gain experience with the new operation, minor adjustments are made to operations at IAH, HOU, and their satellite airports. These include published adjustments to the original procedures, TBFM use, and settings modifications.
"Since this metroplex was on the presidential dashboard being tracked by Congress, we are excited to say, NextGen delivers," said D'Ambrosio.