Flight Information Service: Uplink/Downlink
By Richard L. Collins
Over the years there had been experiments with uplinking weather information. These were done by various entities and none met with success.
In the October, 1998 issue of Flying I wrote about two new systems that were moving forward. One was the Flight Information Services (FIS) system that was being developed by the industry in cahoots with the FAA. The other was dubbed Aviation Weather Information program (AWIN) and was a NASA program.
At the time, the FIS system was to use VHF ground stations. Nothing was specified for AWIN. While it appeared at the time that the FAA and NASA were concurrently developing two separate programs, they were in fact joined, though there was probably a lot of lost motion because two bureaucracies are less efficient than one.
It might seem simple to just beam information up to airplanes, or up to satellites and back down to airplanes, but it took a while, and now, almost six years after it all started, it is becoming more clear what is to be available and how it is going to work.
The Bendix/King system uses a VHF broadcast direct from the ground to the airplane. That makes it easy to explain. If you are in range of one of the ground stations (go to www.bendixking.com, under "Wingman Services" for more information and maps of coverage), you can get weather information. The coverage at 5,000 feet is currently good east of the Rockies and spotty in the west. You have to have a Bendix/King datalink receiver as well as one of the company's MFDs to display the information. It has a special package price of $6,904 for the basic equipment.
This system is a true uplink broadcast system. Once the station has been received for about five minutes the Nexrad radar picture is there and is updated every few minutes. All the other information is there for the whole country, too. It started with metars, TAFs and pireps. Airmets, sigmets and other information are slated to be added about now to some new units and will be available soon for existing ones. Because the FAA was involved in this program and provides the VHF frequencies, the metars, TAFs and pireps are free. As with all the systems, a subscription to the pay part is about $600 a year.
Both Garmin and Avidyne have systems that use low earth orbit satellites to get items of information from the ground and send it to the airplane as requested by the pilot. The thing that is hard to explain about these systems is their predictability. Sometimes the pilot sends a request and the reply comes right back. Sometimes it doesn't come back in a timely manner. That must have something to do with the location and health of the satellite the system is trying to use.
Now there is a satellite-based broadcast system that uses geosynchronous satellites. These are the same as used for the satellite radio systems and have enough bandwidth to support a broadcast system. This system looks at the airplane's present position and the flight plan in the navigator to determine what information is made available to the pilot. The information is all there, but there is a limit to what the equipment can process.