It is important for pilots to understand the realization that the derived safety benefits of data link depends heavily upon the pilot’s understanding of the specific system’s capabilities and limitations which are listed below.
- Product latency—be aware of the time stamp or “valid until” time on the particular data link information displayed in the flightdeck. For example, since initial processing and transmission of NEXRAD data can take several minutes, pilots must assume that data link weather information will always be a minimum of seven to eight minutes older than shown on the time stamp and only use data link weather radar images for broad strategic avoidance of adverse weather.
- Product update cycles—be aware of when and how often a product is updated as well as the Data Link Service Providers (DLSP) update rate for particular products.
- Indication of system failure—be aware of partial or total system failure indications.
- Coverage areas/service volume—coverage limitations are associated with the type of data link network being used. For example, ground-based systems that require a line-of-sight may have relatively limited coverage below 5,000 feet AGL. Satellite-based data link weather systems can have limitations stemming from whether the network is in geosynchronous orbit or low earth orbit. Also, NWS NEXRAD coverage has gaps, especially in the western states.
- Content/format—since service providers often refine or enhance data link products for flightdeck display, pilots must be familiar with the content, format, and meaning of symbols and displays (i.e., the legend) in the specific system.
- Data integrity/limitations to use—reliability of information depicted. Be aware of any applicable disclaimer provided by the service provider.
- Use of equipment/avionics display—pilots remain responsible for the proper use of an electronic flight bag (EFB) or installed avionics. Pilots should be cognizant that, per the FAA Practical Test Standards, they may be evaluated on the use and interpretation of an EFB or installed avionics on the aircraft.
- Overload of Information—most DLSPs offer numerous products with information that can be layered on top of each other. Pilots need to be aware that too much information can have a negative effect on their cognitive work load. Pilots need to manage the amount of information to a level that offers the most pertinent information to that specific flight without creating a distraction. Pilots may need to adjust the amount of information based on numerous factors including, but not limited to, the phase of flight, single pilot operation, autopilot availability, class of airspace, and the weather conditions encountered.