INCREASING NAS CAPACITY

Collaborative air traffic management

New concepts to control and distance aircraft are being implemented. Cockpit-managed separation trials may portend future development for autonomous airspace control.


Overview of the concept of interval management and spacing (IM-S). This would be both ground-based and cockpit-based managed spacing.

Another program to place the information where it is most effective is the Terminal Flight Data Manager. Lockheed Martin was awarded a contract in June 2016 to create the TFDM system. This includes an electronic flight data management system with improved advanced electronic flight strips (AEFS). The prototype AEFS system was created at the FAA's William J Hughes Technical Center to demonstrate how providing tower controllers with a single source of collective information increases efficiency while maintaining safety and situational awareness for each controller in the tower cab.

The 1st tier AEFS system will be replaced with a new flight information system delivered through the TFDM program. TFDM will replace AEFS and the current electronic flight strip transfer system (EFSTS) with a more complete system that will support the NAS long term.

At the PHX traffic control tower where AEFS is currently being used, the AEFS prototype is living up to expectations for the move beyond paper strips. Paper strips require the controller to walk around the tower cab to provide an update. With the new system, information is on one screen and updates are made through touch or a mouse.

To send a strip across the room no longer requires physically walking around, it's just a simple swipe of a finger across the screen. With weather events, runway closures, flow problems and ground stops, the system allows the traffic management unit (TMU) or front line manager (FLM) to enter the information and immediately populate it onto the AEFS screen for all controllers in the tower cab.

Interval Management, Spacing and ADS-B

All of the many programs currently in place and evolving in the near term are driven by the fact that flight crew must react to and follow ATC instructions to make the system work. The 2020 mandate for ADS-B surveillance throughout the NAS and the capability for all aircraft to more cost effectively have a cockpit display of traffic through the ADS-B In function, along with existing TCAS, are leading to interesting research to more effectively integrate the crew into traffic flow management.

Interval management and spacing (IM-S) is a concept that includes the crew in the cockpit who, with specific equipment and procedures, maintain separation behind a specified aircraft using time and/or distance through speed control. MITRE Corp completed a report in 2016 on an aircraft field test to investigate IM-S using optimized descent profiles for arrival and approach.

Over 3 nights UPS Boeing 767s flew optimized profile descents using IM-S for arrival and approach into SDF (Louisville Intl, KY). This was the 1st time revenue aircraft in an actual operational environment invoked traffic separation solely via information in the cockpit. Previous research using simulators for IM-S showed the concept doable and the cockpit workload manageable.

Once the test began, no ATC intervention was necessary. No major problems were noted with communication except some ambiguity as to when flightcrews needed to advise ATC that IM-S procedures were terminated prior to landing. Using a cockpit display of traffic along with the required distances and speed, crews maintained time separation behind a specific lead aircraft. Crews reported they were able to integrate this information into their workload flow. If speed changes were made for other considerations such as 250 KIAS below 10,000 feet, the crew was able to re-capture the re-calculated IM-S speed to fly thereafter.

Sample page from the advanced electronic flight strip program vs a traditional strip board. Prototypes are in use at CLE, EWR, LAS, PHX, and SFO towers, where the swipe of a finger replaces a trip around the cab to propagate flight information to other controllers.

In the "maintain separation" phase of the test, speed changes were directed on average between 100 and 180 second intervals; crews reported this was an acceptable workload. Capture, enroute and approach timing goals were typically reached within +/- 6 to 10 seconds of targets, well within the acceptable limits. When the aircraft-to-follow touched down, most IM-S following aircraft were within +/- 8 seconds of the target goal. However, 2 flights did exhibit low IM-S speed management during the final part of the maintain separation phase; at the touchdown of the aircraft-to-follow, the IM-S following aircraft were 46 and 48 seconds respectively outside of the desired spacing targets.

If a speed change alert was given during configuration for landing, for example, speed capture was delayed. It was found that the further out the IM-S arrival and approach cockpit procedure was initiated, the less impact it had on final segment spacing.

Main reasons for variance from the IM-S desired speed to fly included crews managing spacing based on distance due to ambiguity as to when the IM-S procedure was to start (instructions were to maintain a 22 nm separation and then transition to IM-S speed spacing), crews transiting to final approach speed independent of IM-S speeds, and crews selecting IM-S speeds for the FMS only after out-of-target parameters. Additional real time information from ATC concerning the arrival and terminal environment beyond maintaining the interval management and spacing was deemed necessary to make the procedure flow smoothly.

This test is interesting because it took place in an operational environment. Even with several issues the test was deemed overall to be very successful. ATC did not have to intervene and safety was never at risk of compromise.

IM-S during departure and merging

The concept of flightdeck interval management and spacing (FIM-S) was field-tested for arrival and approach. The long range plan for the NAS is to utilize the new capability of ADS-B in combination with improved cockpit avionics and more sophisticated and integrated ATC programs to separate traffic through both ground-based and flightdeck IM-S. ATC will retain overall responsibility for separation but will assign IM-S to specific aircraft pairs with ATC responsible to terminate and reassign FIM-S as required.

Cockpit crews would also be able to terminate FIM-S if the situation warranted. More work is needed to validate the feasibility of FIM-S, but all studies, simulations and the arrival and approach field test point to FIM-S as a viable method to improve traffic separation efficiency.

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