In meetings and discussions regarding Datalink, the subject of mixed fleet equipage has arisen. It is undeniable that for many years to come, controllers will be handling airspace that includes both datalink equipped and non-datalink equipped aircraft. In addition the type of datalink equipage will differ.

This paper looks at the undesirability of controllers being faced with the responsibility for airspace, within which, the capability to communicate via datalink may be varied, dependent on which type of equipment is carried by the aircraft/operator.

The purchase of Datalink avionics will be determined by the protocols and message sets required and any financial considerations. It is unrealistic to believe that all aircraft owners will update avionics at the same time.

There will be situations where the controller is presented with non-equipped and equipped aircraft, but at differing levels of equipage.

Various methods will be employed to aid the controller in distinguishing between these two groups of aircraft. These may include, equipment designators on flight strips, symbols or letters added to the datablocks on displays, or the use of different colours on displays.

Important human factors work has been done, and more is needed , to determine methods of aiding the controller in distinguishing between datalink and non-datalink equipped aircraft. Studies in the United States, reveal it to be a significantly complex task.

There are several possible methods of dealing with the unavoidable situation of mixed aircraft fleet equipage. One would be to segregate airspace, allowing in only aircraft which meet the minimum level of equipage. This could be implemented through the concept of Required Communications Performance (RCP). Another would be to identify a minimum level of datalink equipage in a particular airspace. An aircraft not meeting this level of equipage, due either to less capable datalink avionics or to lack of recent upgrade version, would still be allowed entry into the airspace but would be handled as a non-datalink aircraft.

To introduce additional complexity with the addition of differing levels of datalink equipage in the same airspace would be undesirable.

There is a requirement for the controller to be aware of the aircraft’s datalink capability to enable the appropriate interchange to take place It is unreasonable that a controller should be called upon, in the same airspace, to identify not only which aircraft are datalink equipped , but also which aircraft have which type of datalink capability, such as, which aircraft were capable of receiving which types of datalink messages.

Information regarding the equipage/ non-equipage of Datalink is notified to controllers at the operational position in the appropriate manner.

The number of types of datalink equipage in a single airspace, should be kept to an absolute minimum.

ATC personnel should not be required to distinguish between different levels of datalink equipage in the same airspace.