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Controller Interface (CPDLC) for NASA LVLASO

Co-Principal Investigators:

  • James Rankin, Ohio University Avionics Engineering Center (previously with St. Cloud State University MN)
  • Patrick Mattson, Associate Professor of Aviation, St. Cloud State University, MN.

Controller Interface
Figure 1: Screenshot of Controller Interface


Research efforts investigated the air traffic controller’s role in NASA-Langley’s Low Visibility Landing and Surface Operations (LVLASO) project. Researching methods and procedures for airport ground traffic as part of NASA’s Terminal Area Productivity Program (TAP) resulted in the definition and design of the necessary Controller Interface (CI) device. This research focuses on 1) the display of traffic information to the controller, 2) the conversion between controller clearances and Data Link formats needed for transmission, and 3) the controller input of clearances per DO-219 specifications. NASA’s overall program goal is to increase airport terminal operations in low visibility conditions to the capacity found in good weather. To achieve this goal, there must be increased situational awareness for both controllers and pilots. The controller must be aware of all traffic on the airport surface. This includes identification, position, direction, and intent. For pilots, situational awareness includes their position, nearby traffic, and a taxi route to their surface destination. Prior experiments at NASA-Langley have shown the benefits of an Electronic Taximap in the flightdeck that displays taxi clearances. These taxi clearances have traditionally been prepared off-line and then datalinked from the controller’s workstation. The CI allows a controller to input taxi commands real-time using Voice Recognition and Touchscreen as well as a mouse, trackball, and/or keyboard. According to Jane’s Airport Review and Aviation Week and Space Technology, three other countries (China, Tahiti, & Russia) have tested similar methods for the enroute environment; this is the first time we know of that the CPDLC is to be used/tested in a terminal environment. The CI is a combination input device and graphical display which is able to transmit, display, and receive clearances with aircraft through data link channel using Voice Recognition and Touchscreen. The CI provides for increased situational awareness for ground controllers including aircraft identification, position, direction, and intent. The protocol for communicating between ATC and aircraft has been defined by Radio Technical Commission for Aeronautics (RTCA) in their Minimum Operational Performance Standards for ATC Two-Way Data Link Communications (DO-2 19) and is incorporated in the CI.

System Description

The CI process converts controller instructions to digitized messages that are formatted according to the RTCA DO-219 standard. The DO-219 messages are transferred via RS-232 to the ATIDS system for uplink using a Mode-S datalink. Pilot acknowledgments of controller messages are downlinked to the ATIDS system and transferred to the CI. In addition to voice recognition, the controller can enter messages using the monitor’s touch screen or by mouse/keyboard. A computer monitor, with touch screen capability, is used to convey information to the controller. Aircraft data from the ARTCC database is displayed on flight strips. The flight strips are electronic versions of the strips currently used in the ATC system. (ARTCC data is accessed from its database by ATII)S and transferred to the CI.) Outgoing controller messages are displayed as message text on the flight strips for reference. A map of the airport with real time traffic is also displayed on the monitor. The CI to ATIDS interface is via RS-232. The CI workstation is hosted on a Pentium-166 PC and is configured to default to COM2 (a 25-pin D-type connector) for the ATIDS interface. COM 1 (a 9-pin D-type connector) is configured for a serial mouse but can be used for the ATIDS interface. The CI is configured as a Data Terminal Equipment (DTE). The datalinked messages follow RTCA protocol outlined in specification DO-2 19. DO-219 provided the requirements for datalink messages between controllers and aircraft in the air. SCSU and NASA defined ground controller communication messages as the RTCA DO-219 did not include these in previous documents. Once the taxi clearance is entered it must be datalinked to the aircraft. We are investigating this system with these specific goals being addressed:

  1. Ease Controller to Pilot communications using datalink
  2. Enhance Ground Controller environment
  3. System should be transparent to controller
  4. More information available to the controller
  5. Uses off-the-shelf electronic equipment
  6. Improve ground-side traffic management
  7. Reduce controller workload.

Specific functions of the CI are:

  1. Voice input of controller instructions.
  2. Converts controller instructions to a digital format to be datalinked to aircraft.
  3. Electronic display of aircraft flight data information.
  4. Display status of datalinked messages after the pilot acknowledges.
  5. “Quick-look” user friendly system.
  6. Taxiway routings can be static (canned) or dynamic.
  7. ROTO is being investigated.

The system is configured using a Pentium 166 MHz processor with 64 MB of RAM and a Verbex voice recognition card, which is used to convert the controllers aural instructions to a digitized format. The Voice Recognition system is trained to recognize specific phrases that are common to the air traffic control environment. We see this as eventually incorporated into the tower VHF radio communications system. The Windows based CI [Figure 2] screen is the primary method for display of communications with aircraft via Controller-Pilot Data Link Communications (CPDLC). The controller, wearing a microphone/headset, aurally gives instructions to aircraft as he/she would with today’s voice radio systems.

Conclusions and further research

Work completed from September 1, 1995 through July 1, 1997 included the software and hardware definition and design, and internal testing using two computer workstations. The results of testing at Atlanta Hartsfield International airport and the NASA-Langley Research Lab (summer 1997) will produce information and data, which needs to be evaluated. Future research efforts are targeted to the integration of the Controller Interface and the Surface Movement Advisor (SMA). Successful design of the CI must include its implementation in the tower environment. The tower is becoming filled with computer displays and terminals. The CI display may be a replacement for the paper strip holder or it may need to be integrated into another display/ terminal. SMA also has direct access to ARTS data that is needed for the flight strips. We are also interested in conducting human factors studies and simulations using ATC Tower simulator. CI functionality is best tested in a flight demonstration similar to Atlanta or Dallas. The benefits to controllers are better tested in a controlled environment. The new ATC Tower Simulation Facility at NASA-Ames provides a location for objectively testing the CI.


Avionics Engineering Center
Russ College of Engineering and Technology
131 McFarland Avionics Building
Ohio University
Athens, OH 45701
Tel: (740) 593-1515

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