Describing the early operational test experience with TMA, Davis recalled, “We put TMA into operation at the Ft. Worth en route air traffic control center and began to test in live traffic. Our engineers would go down there for two weeks at a time and test the system; not for 24 hours a day but for specific busy time periods, maybe five to seven times a day. And of course there were all kinds of safety protocols in place, such as if something started to go wrong they had a way to shut it down. And there were other safety protocols as well.”
In spite of some challenges in early implementation attempts in the late 1990s and early 2000s, the FAA ultimately deployed TMA to all 20 en route centers and some terminal facilities as a traffic management tool.
“But it worked,” he said. “Maybe the early version didn’t work 100 percent of the time, but it worked a lot of the time and really well. And they were starting to gain some efficiency by using it.
“The FAA had had their own metering program in place that generated estimates of when aircraft should arrive at certain points and they presented that in a tabular list on their monochrome radar display,” he said, “Well, TMA was now presenting really accurate predictions and scheduling – like plus or minus half a minute – based on real aircraft models, like genuine models of 737s and 757s and MD-80s. So it was not only a lot more accurate, but it was presenting it in a graphical format with user-interface features to manage the system that turned out to be easier for the traffic managers to use.”
“Over the course of that testing period, which lasted about a year, the controllers reported really liking it. TMA was adding efficiency to the system, so the airlines were, in general, liking it too. They were realizing that metering traffic by time, rather than just separating it by distance, allowed you to land more aircraft and reduce the arrival flight time by a couple minutes per aircraft. So more airplanes were getting on the ground in a shorter period of time and individual flights were saving a minute or two off their flight times. If you say one or two minutes, as a passenger you probably don’t notice it. But as an airline, especially big airlines, you definitely notice it. The accumulation of those savings adds up quickly.”
In spite of some challenges in early implementation attempts in the late 1990s and early 2000s, the FAA ultimately deployed TMA to all 20 en route centers and some terminal facilities as a traffic management tool.
Taking TMA Further
Building on the success of TMA, NASA began researching its next capability developments in programs like Efficient Descent Advisor (EDA); Terminal Sequencing and Spacing (TSS); and Precision Departure Release Capability (PDRC).
Controllers use Efficient Descent Advisor (EDA) in a simulation. Transferred to the FAA in January 2012, EDA works in conjunction with TMA and enables controllers to synchronize the descents of all arriving aircraft so that each can maintain a continuous descent approach, thereby maximizing runway efficiency. NASA image
EDA was transferred to the FAA in January 2012. EDA is a tool for air traffic controllers that synchronizes the descents of all arriving aircraft so that each can maintain a continuous descent approach that minimizes noise and emissions while avoiding other traffic and maximizing runway throughput, rather than the former system that works almost like a series of stair steps at descending flight levels and often included maneuvering on different courses to avoid other air traffic. EDA advises aircraft and controllers of where and when to initiate the descent as well as the speed to maintain in the descent. The tool works in synergy with the TMA tool, which creates a time-based metering arrival schedule that EDA aims to meet with its continuous descent approach solutions for maximum runway efficiency.
TSS was transferred to the FAA in July 2014. It is designed to aid controllers working the airspace known as Terminal Radar Approach Control, or TRACON, helping to determine where each aircraft should be relative to others in order to maintain fuel-efficient, continuous-descent approaches. The TRACON airspace surrounds an airport, beginning five miles from the airport and extending outward about another 35 miles. TSS indicates to controllers at what speed each aircraft should fly in order to maintain spacing with other aircraft and smoothly merge together with other air traffic before being handed off to airport controllers for final approach and clearance to land.
PDRC was transferred to the FAA in 2013. Heavy aircraft traffic at an airport or bad weather can cause fluctuations in departure times, and therefore missed opportunities for the delayed flights to smoothly merge into the flow of high altitude airline traffic. PDRC has two components: a surface model and an en route model. The surface model predicts both departure times and runways, and sends the information to en route centers. PDRC’s en route model then provides climb trajectories from takeoff to the point where the aircraft merges into the high altitude air traffic stream. The tool helps fill slots in the high altitude traffic flow that would otherwise be empty due to delays on the ground at individual airports.
A feature shared by the three most recent transfers – EDA, TSS, and PDRC – is that they were all built on the base TMA technology.