PowerFlarm v3.40

Since you don't have a transponder just set the transponder parameter to negative in the config file and nothing will get suppressed.
You will need to switch to latest firmware sooner or later since previous one will expire.

Ramy

On Sunday, April 13, 2014 6:18:09 PM UTC-7, Ramy wrote:
Since you don't have a transponder just set the transponder parameter to negative in the config file and nothing will get suppressed.

You will need to switch to latest firmware sooner or later since previous one will expire.



Ramy

Do you know if FLARM are working this? The suppression of same altitude mode C targets is a really poor solution to the spurious own transponder alerting problem.


GY

On Friday, April 18, 2014 7:16:26 AM UTC-7, Andy wrote:
On Sunday, April 13, 2014 6:18:09 PM UTC-7, Ramy wrote:

Since you don't have a transponder just set the transponder parameter to negative in the config file and nothing will get suppressed.

You will need to switch to latest firmware sooner or later since previous one will expire.


Ramy

Do you know if FLARM are working this? The suppression of same altitude mode C targets is a really poor solution to the spurious own transponder alerting problem.


Suppression of the local Mode C transponder is done by suppressing same-altitude Mode C targets. That's the main bit of info that the system has to use to do that suppression of the local transponder. Flarm can do things to try to minimize suppression of other transponders but unlike Mode S there is no hard-guaranteed way to suppress only the local Mode C transponder. So this is always going to involve a lot of art as well as science.

Mode S is a different beast where you have a unique ICAO address on each Mode S interrogation. But even a Mode S transponder has to reply to legacy Mode A/C interrogations, and if those are happening then you are back in the same boat. Given that Flarm have been tweaking stuff related to this in recent firmware releases and are warning about same altitude Mode C suppression in 3.4 then I'd assume they are still working on improving all this.

If your or other gliders in the area have Mode S transponders make sure that PowerFLARM and the Mode S transponders in all the gliders are properly configured with the correct ICAO address for those aircraft. And if there is no local transponder follow the advice Ramy already offered.

I suspect that in practice, suppressing transponders at the exact same altitude will have no much affect on PCAS reliability, as relative altitude between aircrafts fluctuate all the time, especially with gliders, and I suspect the suppression algorithm can detect altitude fluctuation and does not suppress it. This is just my guess based on the fact that my PF seem to do good job with PCAS alert even when flying at the same altitude as someone else.

Ramy

On Saturday, April 19, 2014 1:31:15 AM UTC-7, Ramy wrote:
"I suspect that in practice, suppressing transponders at the exact same altitude will have no much affect on PCAS reliability, as relative altitude between aircrafts fluctuate all the time, especially with gliders, and I suspect the suppression algorithm can detect altitude fluctuation and does not suppress it. This is just my guess based on the fact that my PF seem to do good job with PCAS alert even when flying at the same altitude as someone else."

The relative altitude between gliders may be subject to large fluctuations. The relative altitude between powered aircraft is quite likely not to vary by more that the typical 100ft resolution of the altitude encoder interface.

I have first hand experience of being on a same altitude, opposite heading, less that 500ft lateral offset threat. ZAON PCAS alerted. I acquired the aircraft visually then checked PF portable. The target was never indicated or alerted.

ZAON used, perhaps inter alia, the signal strength to determine if a mode C signal is own ship. That is why there is provision in the calibration menus for adjusting each unit for own transponder signal strength. To the best of my knowledge FLARM units have no such provision for user calibration.

Andy

It would be nice to have the option to include a list of transponder codes that were always suppressed. For example, 1202. One could make the determination if a majority of the local gliders with a transponder also had FLARM. If that was a reasonable assessment for your location, then suppressing all the 1202 hits would potentially reduce the false alarms based on transponders and would rely on the more reliable FLARM data.

On Saturday, April 19, 2014 2:49:22 PM UTC-7, wrote:
It would be nice to have the option to include a list of transponder codes that were always suppressed. For example, 1202. One could make the determination if a majority of the local gliders with a transponder also had FLARM. If that was a reasonable assessment for your location, then suppressing all the 1202 hits would potentially reduce the false alarms based on transponders and would rely on the more reliable FLARM data.

Ah the trouble there is you cannot definitively associate a Mode A squawk reply with the same transponder doing a Mode C reply. And there will be situations where targets are doing Mode C only replies (e.g. any time a target is being interrogated by TCAS I or II but out of range of ground SSR... which I'm guessing happens a fair amount).

The 'best' you could do in that situation is stop all PCAS warnings. That may be/is likely too drastic, you can also so try adjusting the PCAS height/range parameters. Ultimately there is nothing you can do that is goign to work that well with Mode C transponders. Hopefully over time this will go away as an issue as Mode S transponder use keeps growing in the USA glider fleet.

There is no need/strong justification to replace a Mode C today, they work great for letting ATC know where you are and with TCAS, TCAD and PCAS in GA aircraft etc. but on the other hand there is no sane reason to buy a new Mode C transponder today. The possible issues here with PowerFLARM interoperability is just one of those reasons. Over time and as equipment ages and gets expensive to repair and new Mode S transponder technology hopefully keeps falling in cost and size etc. we'll just see the current Mode C usage in the glider fleet migrating over to Mode S. I'm much less worried about Mode C vs. Mode S than I am to encourage *any* transponder use in areas of high airline, fast jet, and even GA traffic.

Anybody who what my opinion on what the FAA should have really done with Mode S vs. Mode C transponders and ADS-B Out carriage mandates, etc. is welcome to buy me a six pack of beer and put up with an hour of whining.

On Friday, April 18, 2014 7:31:57 PM UTC-7, darrylr wrote:
"Suppression of the local Mode C transponder is done by suppressing same-altitude Mode C targets. That's the main bit of info that the system has to use to do that suppression of the local transponder. Flarm can do things to try to minimize suppression of other transponders but unlike Mode S there is no hard-guaranteed way to suppress only the local Mode C transponder. So this is always going to involve a lot of art as well as science. "

ZAON worked how to do it without suppressing all same altitude signals but FLARM cannot. That's why I keep my MRX.