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ATM systems are large, very complex and have long life cycles. During their life cycle, ATMs need to undergo frequent upgrades and changes. While some ATM sites use modern hardware and software technology, others rely on older heterogeneous connections of different computers.

These systems may be from different manufacturers or belong to a completely different computer system generation. They often run different versions of an operating system or a different operating system altogether.

During an ATM life cycle, it was often more economic to add new functionality to an existing computer system rather than totally replace or upgrade the existing system. Usually these enhancements were implemented using new add-on technology or better-suited equipment that differed from the base system, e.g. high-performance networks and storage subsystems. This upgrade methodology inherently led to the wide variety of heterogeneous systems.

Potential hazard

  1. Proliferation of new ANS technologies along side legacy systems may complicate maintenance, preclude software reuse, increase training requirements, and increase the potential for human error
  2. Lack of a unifying technical architecture
  3. Different or incompatible communication protocols/data formats, and user interfaces
  4. Support of many older systems is not being provided at the OEM level

Corroborating sources and comments

Whole Airspace ATM System Safety Case – Preliminary Study
A report produced for EUROCONTROL by AEA Technology, Steve Kinnersly

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