PowerFlarm v3.40

Went to update to the latest version of PF--3.40--and one item in the release note made me hesitate:

"Known issues:
- Mode C targets at own altitude may be suppressed."
(http://www.flarm.com/powerflarm/upda...Notes_3_40.txt)

My non-engineer brain assumes that this is related to one of the Fixes in this version:

"FIX: More aggressive suppression of own Mode C XPDR (reverted to 2.60
behaviour)."

Since I don't yet have a transponder in this glider (wag of the finger), and would like better Mode C PCAS alerts than what I'm currently getting (v3.0), I'm wondering if this particular update is one I should skip. Any thoughts/experiences/advice appreciated.

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

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.

Op zondag 13 april 2014 20:05:26 UTC+2 schreef Auxvache:
Went to update to the latest version of PF--3.40--and one item in the release note made me hesitate:

With this update Flarm hopes to reduce the numerous nuisance "dangerous traffic warnings" (DTW).
A nuisance DTW could be described as a warning with red beeping Flarm V3 display or DTW on Butterfly while the traffic that is causing this warning is still at a safe distance.

See photo of such a situation on https://dl.dropboxusercontent.com/u/...ic-warning.jpg
At that time I was climbing in a thermal and the gilder that caused this waring (equipped with transponder with ADS-B out) was flying past me at a distance of 1200 meters.

In Europe a lot of gliders are flying around with mode-s transponders with ADS-B out.
PowerFlarm does not treat the ADS-B signal in the same way as the Flarm signal for a number of reasons.

I have been flying with PowerFlarm for almost a year now and have seen many many nuisance DTW's caused by gliders that have transponders with ADS-B out.
In the mean time I have delivered diagnostic data to Flarm that enables them to improve the firmware and hopefully reduce the number of nuisance DTW's

I certainly hope that Flarm is able to solve this problem soon, because nuisance warnings are also dangerous. I you get used to so much warnings you might not react to a real DTW.

On Tuesday, April 15, 2014 6:51:16 AM UTC-4, RuudH wrote:
Op zondag 13 april 2014 20:05:26 UTC+2 schreef Auxvache:

Went to update to the latest version of PF--3.40--and one item in the release note made me hesitate:



With this update Flarm hopes to reduce the numerous nuisance "dangerous traffic warnings" (DTW).

A nuisance DTW could be described as a warning with red beeping Flarm V3 display or DTW on Butterfly while the traffic that is causing this warning is still at a safe distance.



See photo of such a situation on https://dl.dropboxusercontent.com/u/...ic-warning.jpg

At that time I was climbing in a thermal and the gilder that caused this waring (equipped with transponder with ADS-B out) was flying past me at a distance of 1200 meters.



In Europe a lot of gliders are flying around with mode-s transponders with ADS-B out.

PowerFlarm does not treat the ADS-B signal in the same way as the Flarm signal for a number of reasons.



I have been flying with PowerFlarm for almost a year now and have seen many many nuisance DTW's caused by gliders that have transponders with ADS-B out.

In the mean time I have delivered diagnostic data to Flarm that enables them to improve the firmware and hopefully reduce the number of nuisance DTW's



I certainly hope that Flarm is able to solve this problem soon, because nuisance warnings are also dangerous. I you get used to so much warnings you might not react to a real DTW.

Hmm... interesting that gliders are equipping ADS-B out in Europe. So far
the US has been insisting on a GPS source that costs more than the rest of
the instruments put together. I wonder if this will ever change?

Matt

Just to clarify, the DTW described while can indeed be an issue with ADS-B out equipped gliders, has nothing to do with suppression of own mode C transponder which the OP describes.

Ramy