Thursday, June 23, 2005
RE: Reductions in TIS (Traffic Information Service) coverage
The TIS traffic service provided by ATC became widely available about 2 years ago. TIS allowed the ATC radar data to be up linked to aircraft that had compatible transponders to receive the data (at no cost to the users). Garmin and Honeywell introduced products that allowed aircraft owners to receive the TIS ATC radar data. This data contained the position of nearby aircraft (that may pose a collision threat) and was displayed on an MFD (multi function display) screen in the cockpit. In addition to the graphical display, the pilots would also receive an audio alert if the TIS system perceived a collision threat was developing. Airborne traffic detection systems have been available for a number of years, but TIS was able to provide this solution in the $4500.00 price range rather than $18,000.00 ++ range of TCAS type solutions. TIS became highly desirable and thousands of TIS compatible transponders were installed in aircraft. Garmin alone estimates about 10,000 GTX330 TIS transponders have been installed to date.
I had read several reports
recently about the decommissioning of 22 TIS stations. This was disappointing
news, and I was unable to find additional details on this issue. I made a call
to the FAA in
The program administrator at ACY explained to me that the TIS traffic display comes from the terminal radar system in the approach radar facilities. Computers and software at the ATC ground facility send the traffic information from the terminal radar via the mode S data link to a TIS equipped aircraft in flight. This traffic information is received by the mode S transponder in the aircraft, then displayed on a MFD display in the aircraft cockpit. Center radar does not send TIS information because the update rate is very slow compared to terminal radar. Center radar is about a 12 second sweep, where terminal radar is a 4 second sweep. The FAA feels a 12 second delay is a safety problem when displaying traffic, so no TIS for center radar. Both Garmin and Honeywell have been selling transponders that can retrieve this data (Garmin GTX-330, and the King KT-73) for about 2 years now. There are various MFD screens available that can interface to the TIS transponder and display the traffic information.
The recent news about TIS
reductions is a result of upgrades being made to the ASR radar systems in
select terminal facilities, and budget cuts. At this time, the terminal radar
facilities are running ASR 7, 8, 9, or 11 series systems. All in all there are
about 125 TIS sites (located at various terminal radar facilities across the
Interestingly, there was an internal FAA program to shift the older ASR 7, and 8 systems to other FAA facilities that did not have TIS. So where we lost the TIS feed at one location, that ASR radar (that was TIS capable) was to be relocated to another site (that did not have TIS) and could provide TIS there. If that program had gone through we would not have reduced the total number of TIS sites, only shifted them geographically. Unfortunately, the funding for that program was cut and now it looks like the ASR 7 and 8 (TIS systems), will just be mothballed.
If funding does become available, the ASR 11 systems can be upgraded to provide TIS. This will require a hardware and software upgrade. There is also a 3rd party vendor that has designed a mode S/TIS interface for the ASR 11 systems. This is a solution that will allow the ASR 11 systems to provide TIS service at cost reduced alternative to the hardware and software upgrades. At this point, neither of these solutions has funding.
I did get the feeling speaking with the technical folks at FAA ACY, that they are enthusiastic about TIS, and want to see the system preserved or expanded. Their hands are tied by funding issues beyond their control. Hopefully if this issue gets some attention in the press, we can convince the FAA to release funding to preserve and hopefully expand the TIS coverage.
Peter Stelzenmuller
Penn Avionics, Inc
610-409-0328