NCYankee is correct. A standard GTX330 does not broadcast Lat/Lon even if supplied with GPS data – it just transmits the Mode S address, flight ID or registration (depending on set-up configuration), air/ground status and altitude in addition to the Mode A squawk code. When EHS is enabled it also transmits the mandatory enhanced surveillance parameters (not all aircraft will send all ES parameters – this depends on what they aircraft can provide) but these also don’t include Lat/Lon position.
The upgrade to an ES model is $1200 and then you require either an ARINC734A position source in 429 format or a Garmin- proprietary ADS-B output in RS232 from a Garmin WAAS GPS.
NCYankee wrote:
No, secondary radar is based on transponder and is not a true radar system as is primary radar. With secondary radar, the ground station broadcasts a query on 1030 MHz, and a transponder replies on 1090 MHz. Primary radar involves the radar ground station emitting RF pulses and receiving reflected energy that bounce off an aircraft and are detected by the radar receiver.
OK. A closer look at the shutting down all radars thing in the media, shows it is not entirely accurate. All controlled airfields have TAR (Terminal area surveillance radar) and MSSR (monopulse secondary surveillance radar). It is not these radars that are shutting down. The radars they are shutting down are used for en-route. They will be replaced with WAM/ADS.
NCYankee is correct. A standard GTX330 does not broadcast Lat/Lon even if supplied with GPS data – it just transmits the Mode S address, flight ID or registration (depending on set-up configuration), air/ground status and altitude in addition to the Mode A squawk code. When EHS is enabled it also transmits the mandatory enhanced surveillance parameters (not all aircraft will send all ES parameters – this depends on what they aircraft can provide) but these also don’t include Lat/Lon position.
Which extra parameters were being radiated which necessitated the removal of the GPS-TXP connection referred to in that UK magazine article, in the said large number of TXP installations?
Peter wrote:
Which extra parameters were being radiated which necessitated the removal of the GPS-TXP connection referred to in that UK magazine article, in the said large number of TXP installations?
I don’t know of that case, so can not comment on that. However for your understanding, the data in the table below is EHS. Not all aircraft will indicate all fields. As you can see there is no position information included.
Peter wrote:
I doubt many of the listening squawk units have Mode S capability.
In my experience not only do most of them have Mode S, but they use it very effectively.
I had an intervention from Stansted/Essex the other day. I had been on a flight test to FL250, so had to be with the military. As I descended through the TL, I was given the Regional Pressure Setting and continued down to 2400’ to go below the Stansted shelf.
I squawked and listened on the FMC (“Listening Squawk”) as I always do and almost immediately got “G-ILZZ are you on frequency?”
They asked if I intended to remain below 2500’. It turned out (of course) that RPS was much lower than London QNH and I was 100’ higher than I thought. My stupid oversight, but very quickly dealt with by a very efficient system, which did not need to identify me because they had my Mode S.
My experience (mostly south of the M62) is that whenever TMCs talk to you, they do it by reg, because they have it on Mode S on their screens.
Peter wrote:
Which extra parameters were being radiated which necessitated the removal of the GPS-TXP connection referred to in that UK magazine article, in the said large number of TXP installations?
I think this is an other urban myth. We’ve certainly never been required to remove any GPS wiring interconnection and I don’t know what magazine article you’re referring to. The air-ground status function has no impact on what type of data is being transmitted. I’d be interested to know what ‘Major UK avionics shop’ has had to perform this change on loads of aircraft.
The set-up for EHS parameter output shown in Jesse’s post above has to be configured in the following page so the transmitted data won’t be present unless someone has consciously left the function turned ON when it should have been disabled as part of the basic certification:
The reason for requiring an STC is that EASA wants evidence that the data being transmitted is accurate and consistent as it’s not just an aircraft issue but how the data is used by ATC which is critical. There have been several ADs regarding incorrect EHS data being sent from some Mode S transponders (MST67A and TDR94D come to mind).
The same STC situation now exists for ADS-B systems that are compliant with the 2020 mandate, as ATC will use the data for separation purposes. Systems radiating non-approved GPS data using SIL-0 will be ignored by ATC and so are acceptable under CS-STAN.
LeSving wrote:
Had to read a bit on that WAM thing (Wide Area Multilateration). Avinor has already de-commissioned the primary radars at Sola, Flesland and Værnes. By 2018 only 8 of the 22 radars will be left. By 2035 there will be no air traffic radars left. At the same time they are building this WAM technology. I have never heard of it before, but it will take over completely in Norway, and already have many localized places, also in continental Europe. It requires transponders, mode A/C or S/ADS-B.
They installed a multilateration system here two or three years ago. I’m not entirely certain on all the details, but it still hasn’t been put in service because the CAA so far will not certify it. The vendor is currently paying quite hefty penalty charges to the Isle of Man Government because the project has overrun by such a long time. If it ever gets turned on, we’ll probably have effectively got the system for free.
The idea was to provide coverage over the whole island (the current radar can’t see very far north due to the hills) and better coverage of parts of the Irish Sea.
At the moment we still have the old Watchman rotating away just up the hill from the airport.
Airborne_Again wrote:
The difference is that in the case of primary radar the echo is an actual reflection of the radar signal while in the case of secondary radar the echo is provided by the transponder.
True, but after a set time delay and a transmission on a different frequency.
I think this is an other urban myth. We’ve certainly never been required to remove any GPS wiring interconnection and I don’t know what magazine article you’re referring to. The air-ground status function has no impact on what type of data is being transmitted. I’d be interested to know what ‘Major UK avionics shop’ has had to perform this change on loads of aircraft.
Given this dates from 2007, I had some difficulty finding it, but I have sent you @wigglyamp a pm with the URL of a UK site posting which refers to it. I also clearly recall a UK magazine (the usual magazine; there is only one now I think) article, printed or more probably online since I almost never read the printed one, which was apparently written by the same avionics company, saying they had to disconnect many installations. I am sending it by PM because all that stuff could be fabrication…
The basic idea was that if a GTX330 was connected to a GPS for the purpose of auto AIR/GND switching (a highly desirable feature) it would end up radiating all or most of the stuff arriving on the RS232 or ARINC429 interface, and on aircraft which are supposed to be Elementary Mode S (nearly all GA) this was judged illegal, and then when I asked around people “in the system” I got this reference. The person who sent it to me said he would rather it went away… sleeping dogs and all that.
Some years later, Garmin issued a firmware update which addresses this “illegality” issue, by using the GPS GS for AIR/GND switching but not radiating the GPS parameters. Previous firmware had no config for what would or would not be radiated.
I didn’t know one needs a GTX330 ES to radiate GPS position. But many people do have such a transponder, so what is the difference between that and ADS-B? Both need a GPS with a certain “quality” flag, AIUI.
Peter,
The GTX 330 current software supports EHS, but to be EHS one needs to have all the required inputs. Most GA aircraft don’t have this capability. EHS does not include ADS-B or the GPS position. The GTX 330ES current software supports ADS-B IAW RTCA DO-260B. The data radiated is complex and is ADS-B data, which does include latitude and longitude, but that is only one aspect of what it provides. In the Garmin system, to be compliant with the US ADS-B Out 2020 mandate, one needs to have a valid position source. There are only a few that are approved for this purpose, and the GNS430W/530W, GNS480, and GTN series at a relevant software version are amongst them. A serial interface is used for the Garmin position source for a compliant ADS-B. ARINC 429 can also be used to interface to the GNS/GTN systems. which in many cases was previously wired to the transponder for the purposes of determining mode S ground or airborne status. In the US, some installers did not wire in the serial interface and the GTX 330ES would emit position data but since the ARINC interface did not have any of the other required data, these installations are easily spotted and are identified by the FAA as Non Performing Emitters (NPE). Depending on the specific reasons for NPE status, certified receiver/display systems that comply with the TSO are not allowed to utilize/display an NPE as a target.
