The Design of Reliable Digital Computers for Air Traffic Control

A number of air traffic control authorities are now introducing electronic digital computers into air traffic control systems in order to speed operations and reduce the burden on controllers. These machines will initially be used for the routine clerical and data storage operations, but their full capabilities can only be used if they are given a much greater share of the control task and allowed to make logical decisions and intervene in the handling of the traffic. In such cases the computer will be performing a task that cannot be handed over to a human operator at a moment's notice in the event of a machine failure, and extreme reliability becomes probably the most important single attribute of a computer used in such a system.Although computers of adequate speed and capacity are being produced for commercial and scientific uses, with reliabilities sufficient for these purposes, the frequency of faults and the time required for routine maintenance are both far too large to permit their full-time use in an air traffic control system. The reliabilities of typical components and systems are discussed in the following section.1. The reliability of typical components and systems. The reports of a number of computer users suggest that ‘availabilities’ of 97–99 percent are readily attained, so that only 1–3 percent of the available working time is lost due to unscheduled maintenance.