The near mid-air at the Region 9 contest

[[email protected]]

During the course of our regional at Moriarty we had a very close encounter....something on the order of seven feet. One of the two pilots involved made a comment on twenty three point three regarding the manner in which the other pilot had entered the thermal. That evening our CD Tom Kelly examined the flights using SeeYou and then took both pilots aside (I'm guessing he did this one at a time, but don't know for sure.) The next day Tom presented the data for all to see as a morning safety briefing. He handled this in a most professional manner. No finger pointing, no guilt trips and totally non accusatory. Just the facts as well as what he thought might have lead to the encounter and what might have precluded the incident.( It should be noted that neither pilot was FLARM equipped.) I was very proud of the manner in which brother Kelly handled the situation and would like to say "hats off to Tom Kelly." Zulu

[Ramy]

Thanks for the report and kudus to Tom Kelly.
I dont think it matters much whose fault it was if any, what matters is why none of them was flarm equiped and why we even allow this in contests. After all, a big group of people donated money to offer rental units to those who otherwise insist they don't need it (either since they always fly alone and no one can possibly be in the same area as they do, or because they are super human who can detect any threat even from behind)

Ramy

[Sean F (F2)]

Sounds like Tom handle things very nicely.

Ill just go ahead and say this for the record:

We must make FLARM mandatory at US contests.

IDEA: There are enough rentals to make that happen. Basically the FLARMS should be part of the entry fee. If you not have one you automatically, per a check box in the SSA contest registration (I do not have flarm), you AUTOMATICALLY must pay your $50 rental cost and automatically get one shipped to you at the contest. If you dont have your flarm installed no flying for you. That simple. The CM can then ship them all to the next contet and so on.

Painless, cheap and brilliant. Thoughts?

Back to the near collision. Could you please send the links to these flight traces OR provide the tail numbers and day of the incident? Perhaps the time in the task where the close call occurred so that we can see this ourselves on SeeYou?

Thanks in advance,

Sean

[[email protected]]

On Thursday, June 20, 2013 8:17:22 AM UTC-4, Sean F (F2) wrote:
> Sounds like Tom handle things very nicely. Ill just go ahead and say this for the record: We must make FLARM mandatory at US contests. IDEA: There are enough rentals to make that happen. Basically the FLARMS should be part of the entry fee. If you not have one you automatically, per a check box in the SSA contest registration (I do not have flarm), you AUTOMATICALLY must pay your $50 rental cost and automatically get one shipped to you at the contest. If you dont have your flarm installed no flying for you. That simple. The CM can then ship them all to the next contet and so on. Painless, cheap and brilliant. Thoughts? Back to the near collision. Could you please send the links to these flight traces OR provide the tail numbers and day of the incident? Perhaps the time in the task where the close call occurred so that we can see this ourselves on SeeYou? Thanks in advance, Sean

Based upon what I read above, it sounds like at least one pilot watched the other make a poorly judged entry and followed with a comment. While Flarm has the effect of reducing surprises, it will do nothing to help with poor airmanship. This was demonstrated also at Uvalde.
UH

[Chris Nicholas[_2_]]

UH wrote: “ . . . While Flarm has the effect of reducing surprises, it will do nothing to help with poor airmanship. This was demonstrated also at Uvalde.”

Not ever?

Surely, if both gliders have Flarm and one does “poor airmanship” leading to a likely collision, both Flarms will go into alarm mode. Even the poor airman will sometimes react and do something to avoid a collision, won’t he? Not always maybe, but at least sometimes.

Chris N

[Mike the Strike]

I was flying nearby and heard the radio exchange. The near-collision came as a complete surprise to both pilots. The analysis by Tom at the pilots' meeting was extremely useful and helped us all understand what happened. Kudos to the two pilots for sharing their experience and log files with the rest of us.

It looks as if the thermal had two nearby cores and the two pilots were thermaling at the same altitude but separated horizontally. The pilots were aware of others in the thermal, mostly above them, but at least one of the two in this incident didn't see the other. It may not have been careless flying but bad geometry possibly created a blind spot. Flarm would absolutely have made them aware of this potential conflict. This is why I am now a convert.

This also shows the great value of pilots sharing their mistakes with us and might help explain why those who don't (and I mention no names!) end up not being quite so well-loved by their fellow contestants.

Mike

[Tony[_5_]]

I'd like to echo what Billy and Mike said, I thought Tom and the pilots involved handled the situation really well.

[[email protected]]

On Thursday, June 20, 2013 6:17:22 AM UTC-6, Sean F (F2) wrote:
> Sounds like Tom handle things very nicely.
>
>
>
> Ill just go ahead and say this for the record:
>
>
>
> We must make FLARM mandatory at US contests.
>
>
>
> IDEA: There are enough rentals to make that happen. Basically the FLARMS should be part of the entry fee. If you not have one you automatically, per a check box in the SSA contest registration (I do not have flarm), you AUTOMATICALLY must pay your $50 rental cost and automatically get one shipped to you at the contest. If you dont have your flarm installed no flying for you. That simple. The CM can then ship them all to the next contet and so on.
>
>
>
> Painless, cheap and brilliant. Thoughts?
>
>
>
> Back to the near collision. Could you please send the links to these flight traces OR provide the tail numbers and day of the incident? Perhaps the time in the task where the close call occurred so that we can see this ourselves on SeeYou?
>
>
>
> Thanks in advance,
>
>
>
> Sean

Sean:

Contact Tom for that info.

[Brad[_2_]]

We're the pilots talking to each other on the radio?

I've only flown in 1 contest, but if I recall radio "chatter" was frowned upon.

thanks,
Brad

(who has PowerFlarm and loves it)

[[email protected]]

On Thursday, June 20, 2013 12:41:41 PM UTC-4, Brad wrote:
> We're the pilots talking to each other on the radio? I've only flown in 1 contest, but if I recall radio "chatter" was frowned upon. thanks, Brad (who has PowerFlarm and loves it)

You can ALWAYS make a safety call.
UH

[Wallace Berry[_2_]]

In article >,
Brad > wrote:

> We're the pilots talking to each other on the radio?
>
> I've only flown in 1 contest, but if I recall radio "chatter" was frowned
> upon.
>
> thanks,
> Brad
>
> (who has PowerFlarm and loves it)

"Barking dogs" as Spratt called them, are definitely frowned upon.
However, radio calls in the service of safety are definitely encouraged
by the rules as well as popular opinion. "WB, I'm at your 7 o'clock and
turning inside..." type calls are more than welcome.

[waremark]

About 10 years ago I had s mid-air collision on thermal entry. Happily, neither of us was hurt; we both came down safely on parachutes. If we had both had working Flarms (not available back then) the collision would not have occurred. So I think Flarm/Powerflarm is A GOOD THING.

I have slight reservations about this idea of using rental units at comps. I think you get used to using Flarm over time - the first time I experienced a Flarm warning I jumped out of my skin. And you get used to using it as an aid to scan rather than a distraction from it. Really, it would be better to do that not in a comp environment. And you have to work out how to fix and power the unit safely in your plane.

Mark Burton
London Gliding Club, Dunstable, UK (where Flarm is being adopted quite rapidly by the cross-country community, but it is not compulsory for any type of flying - and Powerflarm and transponders are both very uncommon)

On Thursday, 20 June 2013 19:41:55 UTC+1, WB wrote:
> In article >,
>
> Brad > wrote:
>
>
>
> > We're the pilots talking to each other on the radio?
>
> >
>
> > I've only flown in 1 contest, but if I recall radio "chatter" was frowned
>
> > upon.
>
> >
>
> > thanks,
>
> > Brad
>
> >
>
> > (who has PowerFlarm and loves it)
>
>
>
> "Barking dogs" as Spratt called them, are definitely frowned upon.
>
> However, radio calls in the service of safety are definitely encouraged
>
> by the rules as well as popular opinion. "WB, I'm at your 7 o'clock and
>
> turning inside..." type calls are more than welcome.

[Ramy]

On Thursday, June 20, 2013 5:36:45 PM UTC-7, waremark wrote:
> About 10 years ago I had s mid-air collision on thermal entry. Happily, neither of us was hurt; we both came down safely on parachutes. If we had both had working Flarms (not available back then) the collision would not have occurred. So I think Flarm/Powerflarm is A GOOD THING.
>
>
>
> I have slight reservations about this idea of using rental units at comps.. I think you get used to using Flarm over time - the first time I experienced a Flarm warning I jumped out of my skin. And you get used to using it as an aid to scan rather than a distraction from it. Really, it would be better to do that not in a comp environment. And you have to work out how to fix and power the unit safely in your plane.
>
>
>
> Mark Burton
>
> London Gliding Club, Dunstable, UK (where Flarm is being adopted quite rapidly by the cross-country community, but it is not compulsory for any type of flying - and Powerflarm and transponders are both very uncommon)
>
>
>
> On Thursday, 20 June 2013 19:41:55 UTC+1, WB wrote:
>
> > In article >,
>
> >
>
> > Brad > wrote:
>
> >
>
> >
>
> >
>
> > > We're the pilots talking to each other on the radio?
>
> >
>
> > >
>
> >
>
> > > I've only flown in 1 contest, but if I recall radio "chatter" was frowned
>
> >
>
> > > upon.
>
> >
>
> > >
>
> >
>
> > > thanks,
>
> >
>
> > > Brad
>
> >
>
> > >
>
> >
>
> > > (who has PowerFlarm and loves it)
>
> >
>
> >
>
> >
>
> > "Barking dogs" as Spratt called them, are definitely frowned upon.
>
> >
>
> > However, radio calls in the service of safety are definitely encouraged
>
> >
>
> > by the rules as well as popular opinion. "WB, I'm at your 7 o'clock and
>
> >
>
> > turning inside..." type calls are more than welcome.

One thing worth pointing, that even if someone is totally unfamiliar with how to use the unit, just turning it on and ignoring it or even turning down the volume, may be sufficient since it will still warn others.

Ramy

[[email protected]]

On Thursday, June 20, 2013 5:42:18 PM UTC-7, Ramy wrote:

> One thing worth pointing, that even if someone is totally unfamiliar with how to use the unit, just turning it on and ignoring it or even turning down the volume, may be sufficient since it will still warn others.

I got accommodated to Flarm on the first flight. I think the benefits so far exceed any learning curve concerns that I strongly favor a rental program.. Ramy makes a great point for those with a shallow learning curve. There is definitely momentum towards 100% compliance at contests in the US right now.

9B

[Sean F (F2)]

Agreed...but...I wonder if it would have, at least, better warned one of the pilots who could have made an adjustment to his/her flight path and avoided the close call. FLARM, for me at least, seems to do a very good job of beeping at me if I begin to close on another Flarm equiped glider in thermal entry. And if its really close its always been "going nuts" for many seconds before that potential collision can occur. At the same time if their is no decrease in relatively close range, its silent. As soon as the range begins decreasing, say I turn inside, it immediately warns both pilots by beeping violently. It's a good product.

It's far, far better that nothing I think and this kinda thing is exactly what Flarm is designed to prevent.

Anyhow. I have flarm in both the Lak and Eric just bought a Flarm brick for his 29, installing today for him in Ionia. I have had flarm since 2011 in Uvalde and I never fly without it, even when I fly by myself for power traffic!

How about flarm makes a one time discounted by for US pilots this summer? How about $1499 (the original discount price thru August 31 if 100 pilots join in the group buy)? Lets do something to motivate our fellow pilots to purchase one!

Sean
F2

[mike]

On Thursday, June 20, 2013 6:42:18 PM UTC-6, Ramy wrote:
> On Thursday, June 20, 2013 5:36:45 PM UTC-7, waremark wrote:
>
> > About 10 years ago I had s mid-air collision on thermal entry. Happily, neither of us was hurt; we both came down safely on parachutes. If we had both had working Flarms (not available back then) the collision would not have occurred. So I think Flarm/Powerflarm is A GOOD THING.
>
> >
>
> >
>
> >
>
> > I have slight reservations about this idea of using rental units at comps. I think you get used to using Flarm over time - the first time I experienced a Flarm warning I jumped out of my skin. And you get used to using it as an aid to scan rather than a distraction from it. Really, it would be better to do that not in a comp environment. And you have to work out how to fix and power the unit safely in your plane.
>
> >
>
> >
>
> >
>
> > Mark Burton
>
> >
>
> > London Gliding Club, Dunstable, UK (where Flarm is being adopted quite rapidly by the cross-country community, but it is not compulsory for any type of flying - and Powerflarm and transponders are both very uncommon)
>
> >
>
> >
>
> >
>
> > On Thursday, 20 June 2013 19:41:55 UTC+1, WB wrote:
>
> >
>
> > > In article >,
>
> >
>
> > >
>
> >
>
> > > Brad > wrote:
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > > We're the pilots talking to each other on the radio?
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > I've only flown in 1 contest, but if I recall radio "chatter" was frowned
>
> >
>
> > >
>
> >
>
> > > > upon.
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > thanks,
>
> >
>
> > >
>
> >
>
> > > > Brad
>
> >
>
> > >
>
> >
>
> > > >
>
> >
>
> > >
>
> >
>
> > > > (who has PowerFlarm and loves it)
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > >
>
> >
>
> > > "Barking dogs" as Spratt called them, are definitely frowned upon.
>
> >
>
> > >
>
> >
>
> > > However, radio calls in the service of safety are definitely encouraged
>
> >
>
> > >
>
> >
>
> > > by the rules as well as popular opinion. "WB, I'm at your 7 o'clock and
>
> >
>
> > >
>
> >
>
> > > turning inside..." type calls are more than welcome.
>
>
>
> One thing worth pointing, that even if someone is totally unfamiliar with how to use the unit, just turning it on and ignoring it or even turning down the volume, may be sufficient since it will still warn others.
>
>
>
> Ramy

Doesn't having a transponder also alert the Flarm unit/user?

Mike

[[email protected]]

>
>
> Doesn't having a transponder also alert the Flarm unit/user?
>
>
>
> Mike

Mode S will tell every flarm in miles where you are. Mode C is next to useless for flarm, and many flarm people will have turned mode c warnings down/off.

John Cochrane

[mike]

On Friday, June 21, 2013 1:31:22 PM UTC-6, wrote:
> >
>
> >
>
> > Doesn't having a transponder also alert the Flarm unit/user?
>
> >
>
> >
>
> >
>
> > Mike
>
>
>
> Mode S will tell every flarm in miles where you are. Mode C is next to useless for flarm, and many flarm people will have turned mode c warnings down/off.
>
>
>
> John Cochrane

I remain in stealth mode...with mode c. ;^)

[bumper[_4_]]

On Friday, June 21, 2013 12:31:22 PM UTC-7, wrote:
> >
>
> >
>
> > Doesn't having a transponder also alert the Flarm unit/user?

>
> > Mike
>
>
>
> Mode S will tell every flarm in miles where you are. Mode C is next to useless for flarm, and many flarm people will have turned mode c warnings down/off.
>
>
>
> John Cochrane

That is true IF the Mode S or C is operating in an ATC radar environment, or if it is being actively interrogated by a TCAS equipped aircraft. Otherwise, the flarm or PCAS will never know you're there.

That's part of the beauty of PowerFlarm, unlike a transponder, PF is an active system transmitting your position for other PF users to see.

Both PF and a transponder are important if you fly near gliders or powered aircraft . . . it's not a one or the other deal, though depending on where you fly, one might be more advantageous to have than the other, though both is best.

bumper

[Ramy]

John can you elaborate? That's the first time I hear that there is a difference between mode C and mode S as for PCAS alert? AFAIK both will provide approximate distance, altitude difference and no direction.

Ramy

[Dan Marotta]

To be accurate, it's Mode A (reply code) you're talking about, not Mode C
(pressure altitude). And why would Flarm users filter out signals from
possible threat aircraft? Or did I misunderstand the statement about
turning warnings down/off?

Most of the US air space is covered by ATC radar and so my transponder is
pinging away in reply so I expect Flarm equipped aircraft would see me if
they came into my area. Flying out of Moriarty yesterday, I was one of only
two gliders to stay up and, in 2.1 hours did not get a single blip on my
PCAS. I verified that it was reading my transponder replies by changing my
code and testgin again. I don't think Flarm could have improved my
situation any.

I know I should have simply stayed out of this but... Fire away.


> wrote in message
...
>>
>>
>> Doesn't having a transponder also alert the Flarm unit/user?
>>
>>
>>
>> Mike
>
> Mode S will tell every flarm in miles where you are. Mode C is next to
> useless for flarm, and many flarm people will have turned mode c warnings
> down/off.
>
> John Cochrane

[Darryl Ramm]

On Friday, June 21, 2013 12:31:22 PM UTC-7, wrote:
> >
>
> >
>
> > Doesn't having a transponder also alert the Flarm unit/user?
>
> >
>
> >
>
> >
>
> > Mike
>
>
>
> Mode S will tell every flarm in miles where you are. Mode C is next to useless for flarm, and many flarm people will have turned mode c warnings down/off.
>
>
>
> John Cochrane

Uh? I am willing to listen to economic advice anytime from John but I suspect there is some confusion here and he likely means 1090ES ADS-B. Which is an option on most modern Mode-S transponders but just having "Mode S" does not imply that aircraft transmits 1090ES.. and few especially GA aircraft will today. A threat aircraft with 1090ES data-out will show up with precise location/altitude data on your PowerFLARM, its no longer a PCAS threat with altitude only info. A Mode S (or Mode C) alone transponder in a threat aircraft will only ever present as an altitude only PCAS threat.

There are other compilations with Mode S vs. Mode C. With Mode S a PowerFLARM receiver could in principle do better de-duplciation of threats if that threat aircraft has both Flarm and Mode-S and the Flarm is properly set up to transmit the same unique ICAO address as the Mode S. (then your Flarm receiver can see both the Flarm and Mode-S signals come from the same aircraft). How well PowerFLARM does this in practice I can't comment on.

[Darryl Ramm]

On Saturday, June 22, 2013 9:10:18 AM UTC-7, Dan Marotta wrote:
> To be accurate, it's Mode A (reply code) you're talking about, not Mode C
>
> (pressure altitude). And why would Flarm users filter out signals from
>
> possible threat aircraft? Or did I misunderstand the statement about
>
> turning warnings down/off?
>
>
>
> Most of the US air space is covered by ATC radar and so my transponder is
>
> pinging away in reply so I expect Flarm equipped aircraft would see me if
>
> they came into my area. Flying out of Moriarty yesterday, I was one of only
>
> two gliders to stay up and, in 2.1 hours did not get a single blip on my
>
> PCAS. I verified that it was reading my transponder replies by changing my
>
> code and testgin again. I don't think Flarm could have improved my
>
> situation any.
>
>
>
> I know I should have simply stayed out of this but... Fire away.

There seems to be some confusion here.

To be accurate and correct :-O ...

PCAS typically has *nothing* to do with Mode A replies and is all about Mode C replies. Mode A encodes the squawk code and Mode C encodes the altitude.. A traditional Mode A/C transponder when being interrogated by an SSR system responds to interleaved Mode A and Mode C interrogation pulses (the targets are interrogated multiple times in both Mode A and C each rotation as the SSR interrogator beam sweeps past the aircraft) and responds with whatever its being asked for. PCAS systems, including in the PowerFLARM just listen to those replies and try to guess which ones are mode A or Mode C (the replies don't explicitly say what type they are, traditionally the interrogating SSR knows what it asked for). The PCAS first job is to typically discard any replies it things are mode A and then only using the Mode C replies, work out the altitude of the threat and whether it should display that/issue an alert etc. How well PCAS systems work given they are effectively blind and are have very little data, have to make guesses about Mode C replies and have to infer range from the RF power etc. With Mode S threats PCAS systems can be smarter, e.g. they can absolutely know that a squawk code and altitude transmission comes from the same aircraft etc. There was one older PCAS system that did display threat aircraft squawk codes (e.g. it decoded both Mode A and C) with the claim that its nice to know if a threat is VFR or under ATC control etc. But to me that is all just more info you have to display/let users understand etc. and likely not worth it.

One of the benefits of lots of the special Mode A codes like 1200, 1202, 7700, 7600 is that they do not encode as valid Mode C altitudes but lots of other altitude and squawk codes can alias with each other. This is not an issue when dealing with Mode S transponders being interrogated by a Mode S interrogator.

PCAS clearly cares about Mode C replies because it wants to know the altitude of any threat so it can work out what to do with it, including just ignore it. Mode A does not help much, and with pure Mode A and C transmission in dense traffic environments the PCAS cannot ever tell how to match up Mode C and A replies from the same threat aircraft.

And to complicate things further TCAS and TCAD systems never issue a Mode A interrogation, another reason PCAS never want to rely on anything Mode A, if they just listen to mode A and you were in a TCAS interrogator only environment you would just never ever see the threat. There are some complex second order things that PCAS systems could try to do with Mode A transmissions, but I suspect none of them do.

And to be clear on products here... Flarm equipped aircraft never see any PCAS threats. *PowerFLARM* does see Flarm and PCAS, at least in the USA where all PowerFLARM come with this capability, in other geographies things may be different, for example in Europe "PowerFLARM Pure" does not include PCAS reception capability.

Lots of USA airspace where gliders fly, especially close to terrain/mountains etc. is not covered by SSR and so transponders will not be interrogated by SSR. the obvious pointer here is that controlled airspace has SSR ground interrogator coverage and uncontrolled airspace may not. That will change to some extent as ADS-B rolls out, but hats a who other hairy topic. The savior there frequently is airborne TCAS interrogators, there are lots of airline, private jet and military aircraft flying around issuing mode C (and Mode S, but not Mode A) interrogations and that can be an important factor here to make out PCAS systems work.

Especially in mountainous regions you have to be cautious about PCAS, it might appear to work fine and then suddenly not work as you fly behind an obstruction that shields an SSR ground interrogator or as the overhead TCAS interrogator flies away. Or it might appear to work fine and then as you descent down to pattern altitude you can lose the interrogator yet be exposed to the more dangerous traffic density around an airport.

I'm not sure exactly what point you are making on you PCAS observation out of Moriarty. Assumption about whether you would see other gliders depends firstly on if those other gliders are Mode C or Mode S transponder equipped. And what the local interrogator coverage is, at Moriarty especially when low near the airport, which I assume does rely on TCAS interrogators. Or if you wanted to compare seeing them with PowerFLARM then you need to know if they are PowerFLARM equipped. What exactly was your point here and what are all the other gliders in the area equipped with?

PowerFLARM is clearly superior to PCAS in high-density glider on glider scenarios like contests because of the much more accurate threat information, because more gliders in the fleet are likely to be PowerFLARM equipped than transponder equipped and because there is no issues with needing the Flarm system to be interrogated. Transponders and PCAS have huge benefit when mixing with other traffic (especially gliders carrying transponders where there are high density TCAS equipped fast/commercial jet traffic) and working with ATC etc. Its simply a false paradox to make forced comparisons between transponders vs. PowerFLARM. Owners/pilots should be evaluating what is best for their needs, and that may be to get both.

[[email protected]]

On Saturday, June 22, 2013 11:29:18 AM UTC-7, Darryl Ramm wrote:
> On Saturday, June 22, 2013 9:10:18 AM UTC-7, Dan Marotta wrote:
>
> > To be accurate, it's Mode A (reply code) you're talking about, not Mode C
>
> >
>
> > (pressure altitude). And why would Flarm users filter out signals from
>
> >
>
> > possible threat aircraft? Or did I misunderstand the statement about
>
> >
>
> > turning warnings down/off?
>
> >
>
> >
>
> >
>
> > Most of the US air space is covered by ATC radar and so my transponder is
>
> >
>
> > pinging away in reply so I expect Flarm equipped aircraft would see me if
>
> >
>
> > they came into my area. Flying out of Moriarty yesterday, I was one of only
>
> >
>
> > two gliders to stay up and, in 2.1 hours did not get a single blip on my
>
> >
>
> > PCAS. I verified that it was reading my transponder replies by changing my
>
> >
>
> > code and testgin again. I don't think Flarm could have improved my
>
> >
>
> > situation any.
>
> >
>
> >
>
> >
>
> > I know I should have simply stayed out of this but... Fire away.
>
>
>
> There seems to be some confusion here.
>
>
>
> To be accurate and correct :-O ...
>
>
>
> PCAS typically has *nothing* to do with Mode A replies and is all about Mode C replies. Mode A encodes the squawk code and Mode C encodes the altitude. A traditional Mode A/C transponder when being interrogated by an SSR system responds to interleaved Mode A and Mode C interrogation pulses (the targets are interrogated multiple times in both Mode A and C each rotation as the SSR interrogator beam sweeps past the aircraft) and responds with whatever its being asked for. PCAS systems, including in the PowerFLARM just listen to those replies and try to guess which ones are mode A or Mode C (the replies don't explicitly say what type they are, traditionally the interrogating SSR knows what it asked for). The PCAS first job is to typically discard any replies it things are mode A and then only using the Mode C replies, work out the altitude of the threat and whether it should display that/issue an alert etc. How well PCAS systems work given they are effectively blind and are have very little data, have to make guesses about Mode C replies and have to infer range from the RF power etc. With Mode S threats PCAS systems can be smarter, e.g. they can absolutely know that a squawk code and altitude transmission comes from the same aircraft etc. There was one older PCAS system that did display threat aircraft squawk codes (e.g. it decoded both Mode A and C) with the claim that its nice to know if a threat is VFR or under ATC control etc. But to me that is all just more info you have to display/let users understand etc. and likely not worth it.
>
>
>
> One of the benefits of lots of the special Mode A codes like 1200, 1202, 7700, 7600 is that they do not encode as valid Mode C altitudes but lots of other altitude and squawk codes can alias with each other. This is not an issue when dealing with Mode S transponders being interrogated by a Mode S interrogator.
>
>
>
> PCAS clearly cares about Mode C replies because it wants to know the altitude of any threat so it can work out what to do with it, including just ignore it. Mode A does not help much, and with pure Mode A and C transmission in dense traffic environments the PCAS cannot ever tell how to match up Mode C and A replies from the same threat aircraft.
>
>
>
> And to complicate things further TCAS and TCAD systems never issue a Mode A interrogation, another reason PCAS never want to rely on anything Mode A, if they just listen to mode A and you were in a TCAS interrogator only environment you would just never ever see the threat. There are some complex second order things that PCAS systems could try to do with Mode A transmissions, but I suspect none of them do.
>
>
>
> And to be clear on products here... Flarm equipped aircraft never see any PCAS threats. *PowerFLARM* does see Flarm and PCAS, at least in the USA where all PowerFLARM come with this capability, in other geographies things may be different, for example in Europe "PowerFLARM Pure" does not include PCAS reception capability.
>
>
>
> Lots of USA airspace where gliders fly, especially close to terrain/mountains etc. is not covered by SSR and so transponders will not be interrogated by SSR. the obvious pointer here is that controlled airspace has SSR ground interrogator coverage and uncontrolled airspace may not. That will change to some extent as ADS-B rolls out, but hats a who other hairy topic. The savior there frequently is airborne TCAS interrogators, there are lots of airline, private jet and military aircraft flying around issuing mode C (and Mode S, but not Mode A) interrogations and that can be an important factor here to make out PCAS systems work.
>
>
>
> Especially in mountainous regions you have to be cautious about PCAS, it might appear to work fine and then suddenly not work as you fly behind an obstruction that shields an SSR ground interrogator or as the overhead TCAS interrogator flies away. Or it might appear to work fine and then as you descent down to pattern altitude you can lose the interrogator yet be exposed to the more dangerous traffic density around an airport.
>
>
>
> I'm not sure exactly what point you are making on you PCAS observation out of Moriarty. Assumption about whether you would see other gliders depends firstly on if those other gliders are Mode C or Mode S transponder equipped. And what the local interrogator coverage is, at Moriarty especially when low near the airport, which I assume does rely on TCAS interrogators. Or if you wanted to compare seeing them with PowerFLARM then you need to know if they are PowerFLARM equipped. What exactly was your point here and what are all the other gliders in the area equipped with?
>
>
>
> PowerFLARM is clearly superior to PCAS in high-density glider on glider scenarios like contests because of the much more accurate threat information, because more gliders in the fleet are likely to be PowerFLARM equipped than transponder equipped and because there is no issues with needing the Flarm system to be interrogated. Transponders and PCAS have huge benefit when mixing with other traffic (especially gliders carrying transponders where there are high density TCAS equipped fast/commercial jet traffic) and working with ATC etc. Its simply a false paradox to make forced comparisons between transponders vs. PowerFLARM. Owners/pilots should be evaluating what is best for their needs, and that may be to get both.



Yup - what Darryl said.

I got a transponder because I frequently fly at Minden. But of the last two glider friends I lost to midairs neither collided with a commercial aircraft and I believe both were outside or below airspace where PCAS could help you. One was a high density glider contest situation and the other hit the only other airplane in the vicinity - in the pattern. That doesn't even consider all the non-fatal collisions and near misses. Even at Minden before getting a transponder I was never surprised by an airliner, but frequently by gliders. In both cases I'm sure there were threats I missed, but given that jets and props make noise and glider don't I'm pretty sure that I missed more glider threats than powered ones.

I also find the lack of PCAS bearing and reliable range info particularly debilitating, though I'll take what I can get if it's the only game in town in high density commercial areas. If I knew how would turn off the PCAS warnings in a situation where I was flying a contest located outside of powered traffic areas simply because I would not want all the useless warnings distracting me from the useful ones.

Of course, that's just my situation.

9B

[Dan Marotta]

Wow! That was an education on how the system works and I certainly need to
study some more.

Regarding PCAS and how I use it in *my* environment, it's not so much a
bearing/distance/height pointer showing me where to look, as it is watching
the distance/delta height and noting whether it's closing, matching, or
diverging from my flight path.

I think you nailed it in your last sentence: "Owners/pilots should be
evaluating what is best for their needs, and that may be to get both."


"Darryl Ramm" > wrote in message
...
On Saturday, June 22, 2013 9:10:18 AM UTC-7, Dan Marotta wrote:
> To be accurate, it's Mode A (reply code) you're talking about, not Mode C
>
> (pressure altitude). And why would Flarm users filter out signals from
>
> possible threat aircraft? Or did I misunderstand the statement about
>
> turning warnings down/off?
>
>
>
> Most of the US air space is covered by ATC radar and so my transponder is
>
> pinging away in reply so I expect Flarm equipped aircraft would see me if
>
> they came into my area. Flying out of Moriarty yesterday, I was one of
> only
>
> two gliders to stay up and, in 2.1 hours did not get a single blip on my
>
> PCAS. I verified that it was reading my transponder replies by changing
> my
>
> code and testgin again. I don't think Flarm could have improved my
>
> situation any.
>
>
>
> I know I should have simply stayed out of this but... Fire away.

There seems to be some confusion here.

To be accurate and correct :-O ...

PCAS typically has *nothing* to do with Mode A replies and is all about Mode
C replies. Mode A encodes the squawk code and Mode C encodes the altitude. A
traditional Mode A/C transponder when being interrogated by an SSR system
responds to interleaved Mode A and Mode C interrogation pulses (the targets
are interrogated multiple times in both Mode A and C each rotation as the
SSR interrogator beam sweeps past the aircraft) and responds with whatever
its being asked for. PCAS systems, including in the PowerFLARM just listen
to those replies and try to guess which ones are mode A or Mode C (the
replies don't explicitly say what type they are, traditionally the
interrogating SSR knows what it asked for). The PCAS first job is to
typically discard any replies it things are mode A and then only using the
Mode C replies, work out the altitude of the threat and whether it should
display that/issue an alert etc. How well PCAS systems work given they are
effectively blind and are have very little data, have to make guesses about
Mode C replies and have to infer range from the RF power etc. With Mode S
threats PCAS systems can be smarter, e.g. they can absolutely know that a
squawk code and altitude transmission comes from the same aircraft etc.
There was one older PCAS system that did display threat aircraft squawk
codes (e.g. it decoded both Mode A and C) with the claim that its nice to
know if a threat is VFR or under ATC control etc. But to me that is all just
more info you have to display/let users understand etc. and likely not worth
it.

One of the benefits of lots of the special Mode A codes like 1200, 1202,
7700, 7600 is that they do not encode as valid Mode C altitudes but lots of
other altitude and squawk codes can alias with each other. This is not an
issue when dealing with Mode S transponders being interrogated by a Mode S
interrogator.

PCAS clearly cares about Mode C replies because it wants to know the
altitude of any threat so it can work out what to do with it, including just
ignore it. Mode A does not help much, and with pure Mode A and C
transmission in dense traffic environments the PCAS cannot ever tell how to
match up Mode C and A replies from the same threat aircraft.

And to complicate things further TCAS and TCAD systems never issue a Mode A
interrogation, another reason PCAS never want to rely on anything Mode A, if
they just listen to mode A and you were in a TCAS interrogator only
environment you would just never ever see the threat. There are some complex
second order things that PCAS systems could try to do with Mode A
transmissions, but I suspect none of them do.

And to be clear on products here... Flarm equipped aircraft never see any
PCAS threats. *PowerFLARM* does see Flarm and PCAS, at least in the USA
where all PowerFLARM come with this capability, in other geographies things
may be different, for example in Europe "PowerFLARM Pure" does not include
PCAS reception capability.

Lots of USA airspace where gliders fly, especially close to
terrain/mountains etc. is not covered by SSR and so transponders will not be
interrogated by SSR. the obvious pointer here is that controlled airspace
has SSR ground interrogator coverage and uncontrolled airspace may not. That
will change to some extent as ADS-B rolls out, but hats a who other hairy
topic. The savior there frequently is airborne TCAS interrogators, there are
lots of airline, private jet and military aircraft flying around issuing
mode C (and Mode S, but not Mode A) interrogations and that can be an
important factor here to make out PCAS systems work.

Especially in mountainous regions you have to be cautious about PCAS, it
might appear to work fine and then suddenly not work as you fly behind an
obstruction that shields an SSR ground interrogator or as the overhead TCAS
interrogator flies away. Or it might appear to work fine and then as you
descent down to pattern altitude you can lose the interrogator yet be
exposed to the more dangerous traffic density around an airport.

I'm not sure exactly what point you are making on you PCAS observation out
of Moriarty. Assumption about whether you would see other gliders depends
firstly on if those other gliders are Mode C or Mode S transponder equipped.
And what the local interrogator coverage is, at Moriarty especially when low
near the airport, which I assume does rely on TCAS interrogators. Or if you
wanted to compare seeing them with PowerFLARM then you need to know if they
are PowerFLARM equipped. What exactly was your point here and what are all
the other gliders in the area equipped with?

PowerFLARM is clearly superior to PCAS in high-density glider on glider
scenarios like contests because of the much more accurate threat
information, because more gliders in the fleet are likely to be PowerFLARM
equipped than transponder equipped and because there is no issues with
needing the Flarm system to be interrogated. Transponders and PCAS have huge
benefit when mixing with other traffic (especially gliders carrying
transponders where there are high density TCAS equipped fast/commercial jet
traffic) and working with ATC etc. Its simply a false paradox to make forced
comparisons between transponders vs. PowerFLARM. Owners/pilots should be
evaluating what is best for their needs, and that may be to get both.

[jfitch]

Question: is there pressure to equip towplanes at contests and for that matter generally with Flarm? The only recent midair in our area between light aircraft was glider and towplane. If the towplane didn't have a Flarm then it would not have helped. Where I fly I am much more likely to be close to a towplane than any other light aircraft (except other gliders), and I don't take tows.

[Darryl Ramm]

On Saturday, June 22, 2013 7:54:31 PM UTC-7, jfitch wrote:
> Question: is there pressure to equip towplanes at contests and for that matter generally with Flarm? The only recent midair in our area between light aircraft was glider and towplane. If the towplane didn't have a Flarm then it would not have helped. Where I fly I am much more likely to be close to a towplane than any other light aircraft (except other gliders), and I don't take tows.

Yes. And I believe that contest organizers can also use the PowerFLARM rental program for towplanes (see http://www.williamssoaring.com/powerflarm/rent.html). And some clubs/FBOs are already there with PowerFLARM equipped towplanes. Ask the operation where you fly and if they don't then it sounds like a great local education and financial issue you can work on with the owners/operator/club