1.544 Mb/s: flight simulators now soar to realism.
NOW SOAR TO REALISM
Embry-Riddle Aeronautical University, Daytona Beach, Fla., wanted to connect pilot training facilities in one building to a VAX and air traffic control simulation panel in another.
The voice and data link would create a realistic flight environment for pilot and controller, simulating common air traffic scenarios and flying situations.
And it would have to be able to expand to meet future needs.
"We try to avoid 'single purpose' solutions which limit the utility of the components involved," says Howard Muffler, manager of systems and communications. "Ideally, the equipment should function in multi-purpose roles and serve as building blocks."
Beyond The Obvious
"A short-term solution would be to put in some type of line driver," adds Dave Cochran, systems programmer, "but our attitude is to look beyond the obvious."
Acting as in-house consultants to Jim Blanchard, Airway Science Simulation Laboratory equipment manager, Muffler and Cochran specified a cost-effective solution for Embry-Riddle's immediate project needs.
Redundancy was highly important given the critical nature of the application.
Moreover, the solution had to be compatible with DS3 or higher bandwidth backbones and the addition of locations, both domestic and international.
It had to maximize capital investment while making use of a large existing fiber-optic cable plant.
The information processing side of the link is split between two areas. One segment connects to a DEC VAX port operating asynchronously at 9.6 kb/s, the other to a controller panel in the air traffic control laboratory.
The other end of the link connects to the pilot training laboratory in the flight center housing eight Frasca trainers (working replicas of single-engine aircraft cockpits).
Each Frasca sends numerical data via serial interface.
The data consists of altitude, air speed, compass heading and other information related to an aircraft's operation and movement.
In addition, each Frasca contains a simulated two-way radio link between cockpit and instructor console.
The voice side of the two Canoga-Perkins Model 3140 T1 voice/data multiplexers connects to the air traffic control laboratory in place of the console's microphone and speaker.
The numerical data contains the frequencies to which the Frasca's on-board radios are tuned.
Since the voice circuits weren't directly compatible with the 3140's typical E&M channel cards, they were modified by utilizing blocking capacitors to match the DC in the trainers and to provide a lower-level audio I/O to the 3140 voice circuits.
The voice circuits now connect via the high impedance side of the radio transmitter to the E&M card, rather than via the 75-ohm side.
Canoga-Perkins technicians reviewed the Frasca schematics with Cochran and identified two alternate modifications to bring the Frasca in spec with the 3140.
They drew up the specs for the changes and provided them to Blanchard.
The simulator's microphone feeds into one of the 3140's E&M cards, and the voice signal travels over fiber into the control room's 3140.
The data from the simulator goes from the trainer through the multiplexer and into the control room's VAX.
A software program in the control room queries the trainers, allowing the relative positions of the eight Frascas to be tracked on a simulated radar scope as if the Frascas were airborne.
This is accomplished by passing the data through the VAX, which processes the information and formats it for the radar display.
Each Frasca appears on radar exactly as it would in actual operation and in proper relation to the other trainers.
The voice signal goes to the control room, where an operator can toggle a switch to become "ground," "tower," or any other air traffic control radio service.
The simulation will expand to include several major airports and the services appropriate to those facilities. Actual helicopter traffic from the Washington D.C. area will be brought in via satellite link.
Finally, PC-bases simulators to add aircraft will be tied to the VAX to enhance the overall effect. This will simply require additional 3140 channel cards for the extra serial ports.
The key to this application, and undoubtedly many more, was Embry-Riddle's fiber-optic cable network, using a hybrid star topography.
"Strategic campus buildings are connected to the major fiber trunks and used as 'hubs' for other areas," Cochran says. "This type of dispersion allows for cost reductions in bringing new applications on line and eases the impact of future needs."
The fiber-optic cable network speeds access to virtually every communications center on campus.
Standards specified directly by Muffler and Cochran for fiber-optic installation are rigid.
All underground fiber is buried at a minimum depth of 4 feet in 4-inch PVC conduit. The bend radius for any turn cannot be less than 3 feet. The fiber is selected for its durability and life span in an underground environment.
Founded in 1926, Embry-Riddle has more than 13,000 students worldwide.
Aside from Daytona Beach, there's also a campus in Prescott, Ariz.
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|Title Annotation:||the first of seven case studies on implementing T1 networks|
|Date:||Oct 1, 1990|
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