As air traffic increases in Europe, navigation and safety are becoming critical issues. As a result, the European Community is revamping its air traffic safety systems. Eurocontrol, an independent European organization, oversees air navigation safety for its 16 member states. The members have joined forces to develop new systems and to gradually upgrade existing navigation systems throughout Europe.

There are five Eurocontrol centers in Europe, each one responsible for different project activities. At the Eurocontrol Experimental Center south of Paris, developers are working on collision avoidance software and a mathematical simulator using object oriented technology, the Booch method, Rational Rose, and Ada.

The Reorganized ATC Mathematical Simulator (RAMS) program is a simulator developed and used in house by the Eurocontrol Experimental Center. RAMS is also used by external groups, such as national aviation organizations. The RAMS program simulates different air patterns, enabling researchers to study a new section of air space and new monitoring procedures. The RAMS project consists of about 100,000 lines of code and required 15 man years of development work.

The Airborne Collision Avoidance System (ACAS) program is a safety system simulator that consists of more than 40,000 lines of Ada code, required six man years of development work, and was completed two months ahead of schedule.

For each of these projects, the development teams adopted an iterative approach, and used the Ada programming language. For the design phase, Eurocontrol used the Booch method and Rational Rose. By using an object oriented design approach, developers were able to take full advantage of many of the features and benefits of the Ada language, including abstraction and information hiding.

"Once we had decided to take an iterative, object oriented approach to the project, we needed to select an effective methodology," explain Michael Lott, head of software-engineering unit at Eurocontrol. "We needed a method that was well-defined by a recognized expert. This method also had to be supported by several tools. We selected the Booch method and Rational Rose based on these criteria."

The primary reasons for selecting an iterative, object oriented approach were maintainability, flexibility, and reusability of the software over its lifetime, which Eurocontrol estimates to be from 12 to 15 years.

"Many of our projects are maintained over long periods of time and are modified regularly," says Lott. "For example, our real time simulator needs to be modified for most specific simulations, and the software must be adaptable. With object-oriented technology, we are able to simplify this process."