"Paired Approach in a Suitcase" Integrates FAA and MITRE Capabilities

November 2014
Topics: Modeling and Simulation, Air Traffic Management, Airports, Aviation Industry
A convergence of FAA initiative and MITRE innovation made it possible to conduct simulations necessary to initiate the early stages of a new flight procedure. They did it by teaming up to modify two of the FAA's high-fidelity aircraft simulators.
Plane taking off.

The new flight procedure, Paired Approach, is designed to enable aircraft to safely land on closely spaced parallel runways in adverse weather conditions, when visibility is poor—and to do so with separation distances that were previously impossible. This, in turn, will improve capacity at airports with these runway configurations.

The Paired Approach relies on sensor technology called Automatic Dependent Surveillance-Broadcast (ADS-B), which receives surveillance information from nearby aircraft and displays it on a screen in the cockpit for the pilot's use. The Paired Approach procedure uses this technology to allow pilots to perform low-visibility approaches on select pairs of closely spaced parallel runways at aircraft separation distances approaching those allowed in periods of high visibility.

To execute a safe and efficient Paired Approach using this new procedure, the aircraft approaching the two parallel runways must maintain a predetermined distance from one another. "One aircraft must be in the 'lead' position and another in the 'trail' position, and they must maintain a separation of about one-half mile to 1 mile from one another," explains MITRE group leader Brennan Haltli.

To help pilots achieve this crucial separation, MITRE researchers developed the concept of a "safe separation window" with front and rear "gates" as buffers for protection against such dangers as wake vortices. The ensuing prototype technology MITRE developed displays the front and rear gates of the safe separation window on a screen in the cockpit, along with algorithms that generate speed commands when the pilot is flying too fast or too slowly to remain in the window. If the pilot violates either the front or rear gate, the prototype system delivers a command for the pilot to execute a predefined “breakout” procedure to ensure the safety of the two aircraft.

Simulator Technology that Feels Like the Real Thing

During the last two years, the FAA and MITRE tested the technology and procedures in MITRE's labs in McLean, Virginia. MITRE also provided the FAA with a feasibility analysis and a preliminary requirements analysis. That work readied the technology for testing at the FAA's Oklahoma City facility, which features two high-fidelity flight simulators—a Boeing 737-800 NG and an Airbus 330/340. Staff used them to test and analyze new procedures and flight-deck technologies.

These multi-million-dollar simulators, designated Level D, are the highest-grade flight simulators available. They mimic the actual flight characteristics and flight-deck environment and conditions a pilot might experience when flying these planes. Seated on huge hydraulic or electric platforms, they bounce, shake, and tilt. All the buttons are functional. And they are capable of simulating virtually any emergency, from engine loss to severe turbulence. To the pilot, it feels like the real thing.

Because of their incredible fidelity, the FAA uses these simulators in a research environment to test and certify new concepts, procedures, and technologies. When building a new or non-standard procedure, the FAA flies it in its Level D simulators to validate the procedure construction and flyability.

Earlier this year, the FAA concluded that the Paired Approach concept and MITRE's associated prototype equipment were suitably mature for evaluation in the Level D systems. But testing the procedure required Paired Approach display features that didn't then exist on the Oklahoma City simulators' cockpit display of traffic information (CDTI) and ADS-B guidance display (AGD). The latter display provides airspeed commands to pilots to help them remain in the Paired Approach safe separation window.

Photo used with permission from the FAA. The Airbus 330/340 high-fidelity aircraft simulator at Oklahoma City.

Integrating MITRE Displays into the Simulator

Engineers in the FAA's Flight Standards Flight Technologies and Procedures Division, in collaboration with their MITRE counterparts, developed a plan to incorporate MITRE's equipment with the FAA's simulators. Together they created a design for adding the AGD and the CDTI into the simulators while running the Paired Approach algorithms on portable, external systems, an approach that soon became known as "Paired Approach in a suitcase."

A cockpit display of traffic information (CDTI)-left, and an ADS-B guidance display (AGD)-right, provide airspeed commands to pilots to help them remain in the Paired Approach window.

Members of the MITRE team went to Oklahoma City, where they worked closely with FAA engineers who integrated and installed the modified CDTI and AGD into the simulators.

In addition to handling the technical requirements and simulator data interfaces, FAA leads worked with a metal shop to create mounts for the prototype displays that would make the installations realistic. The goal was to ensure pilots experience the displays as being part of the design of the jet's cockpit.

Incorporating MITRE's equipment into the FAA's simulators proved to be an effective approach. In June 2014, the FAA brought in 10 Airbus-qualified crews to test the Paired Approach procedure and provide their feedback. By all accounts, the simulation was successful. The FAA came away with plenty of objective data—such as how long it took pilots to adjust their speed once they received a new speed command. Equally important, they gathered human factors data, such as the pilots' perceptions of feasibility of the Paired Approach procedure, the additional workload it presented, and their suggestions for improving the displays. The FAA will feed the data collected from the testing in Oklahoma City into a fast-time Monte Carlo simulation to enable a more refined safety assessment.

Pairing Technology Beyond Paired Approach

An unexpected outcome of retrofitting the FAA's simulators with MITRE's Paired Approach in a suitcase technology is that the agency wants to retain the system and use it to perform other ADS-B applications testing to inform concepts and avionics performance standards. MITRE will prototype the display elements and the algorithms for emerging ADS-B applications, many of them in development in RTCA, and then the FAA can upload the new software into the MITRE auxiliary displays in its simulators. This option is expected to help the FAA assess new operating concepts sooner in the development process and move forward with NextGen flight-deck capabilities in a cost-effective manner.

—by Marlis McCollum

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