Flarm in the US

On Aug 11, 11:55*am, Westbender wrote:
On Aug 11, 10:41*am, Dave Nadler wrote:



On Aug 11, 11:27*am, Westbender wrote:

On Aug 11, 10:09*am, mattm wrote:

On Aug 11, 10:41*am, Westbender wrote:

Forgive me if this is a really dumb question. I don't know much about
transponder operation.

Is it a technical requirement for a transponder to only transmit when
it's been interrogated by a ping from a remote source? I'm just
wondering why transponders can't have a "timeout" mechanism built into
it where it will automatically report/transmit if it hasn't been
pinged in a certain amount of time. Something like a 30 second
timeout? Maybe user-selectable? For the folks who fly in remote areas,
wouldn't something like this help? Or is the transponder response of
no use without pairing it with a request (ping)?

That's the meaning of "transponder" -- it transmits a response (to a
radar paint), plus it includes additional information. *It goes back
to
WWII days when it was originally known as IFF -- Identify Friend or
Foe. *The detection methods based on transponder response depend
on the timing between when the primary pulse is seen and the response.
The larger the duration, the further from the transponder you are.

This is the point of the FLARM scheme -- all the units periodically
broadcast their status, so they are visible even when there is no
radar around.

-- Matt

When I read the "how it works" on the Zaon website, it says it reads
the response. It doesn't say anything about using the primary pulse in
it's process. Is that typical of PCAS systems?

This is where my question originates. It seems that the PCAS system
might not need the initial request from a radar to evaluate threats.
If so, then wouldn't an aircraft transponder "replying" without a
radar pulse give surrounding aircraft with PCAS the means to detect?

A PCAS system replies on someone else interrogating the
transponders. "Someone" is either a ground radar station or
a TCAS-II equipped aircraft. If you are in a valley without
radar and without overflying jets, you will hear nothing.

Hope that helps,
Best Regards, Dave- Hide quoted text -

- Show quoted text -

Right, did you read my first post?

Since the MRX PCAS (passive) only uses the reply from transponders,
wouldn't it be nice if the trig had a timed/scheduled transmit when
not interrogated for a certain amount of time? If so, a combination of
a trig/PCAS would be relatively inexpensive for glider-to-glider
detection (yeah, yeah, assuming everyone had that combo). The best
part would be the benefits of the "normal" operating mode of the trig
and PCAS in relation to other GA and commercial aircraft.

What are the ramifications of doing something such a thing?

You CANNOT do that.
You will never get approval for transmissions on 1090...

Hope that's clear,
Best Regards, Dave

On Aug 11, 8:07*am, William Gagen wrote:
FLARM - We NEED it yesterday.

How many more midairs do we need to have in our sport?

What if we have a midair with an airliner? Can you say soaring as a
sport is dead, as the FAA will reflexively eliminate all of our
flexibility.

The cost of FLARM in any form is negligible compared to staying
alive.

I have used FLARM at the IMGC Competition (International Military
Glider Comp) in Germany, and it turned a competition with 93 gliders
into the safest competition I have ever flown in anywhere.

It provides timely, accurate, important alerts for collision potential
with very few spurious or distracting warnings. It is vastly superior
to PCAS. There is absolutely no reason we shouldn't be requiring it
for all competition aircraft PERIOD!

The following midairs could all have been prevented by FLARM: Parowan
this summer, Uvalde this summer, Boulder last winter, the Hudson River
helicopter/light plane midair.

Thanks for reading my rant. But, having used it, I know how good it
is, and why we need it yesterday!

SSA could be helpful by providing loaner or rental FLARM units to
aircraft to use in competitions. In this way, we could get them into
every competition sooner. A pilot could rent a unit for say $100 a
competition, and over 2 summers the units would be paid off.

There is a gamut of collision scenarios from glider-glider, glider-
towplane, glider-GA, glider-fast-jet and glider-airliner and there is
no single technology or single product that well addresses all these
problems. The first thing in thinking about collision avoidance is to
be very clear just what problem(s) you are trying to solve.

I agree that Flarm and (and in the USA the flarm-flarm part of
PowerFLARM product) can be a significant help in glide-glider and
glider-towplane collision scenarios and I agree that the collision
with an airliner is a horrible scenario, for the innocent passengers
and crew, and would cause incredible damage to our sport. However
unfortunately this post seems to jumble up too much of all this
collision avoidance/traffic awareness technology and the capabilities
and benefits and that worries me.

The post talks about "flarm" helping with airliner collision avoidance
and that is a dangerous claim to make without some careful
qualification and is certainly not true with with the traditional
flarm product in Europe. Flarm (the flarm-flarm protocol) has nothing
to do with avoiding airliner collisions. Airliners and fast jets (and
most GA traffic outside of say tow planes) just will not be able to
receive or transmit the flarm protocol and the flarm protocol does not
make a glider visible to ATC.

The PowerFLARM product with 1090ES can receiver ADS-B over 1090ES.
Most airliners, fast jets and GA aircraft are not yet equipped with
1090ES data out. Rule for ADS-B equipage vary between Europe and the
USA, all airliners eventually will have 1090ES data-out but I don't
think anybody has good timelines yet for when a significant fraction
of them will be equipped. Once 1090ES data-out equipped a PowerFLARM
would "see" that traffic via 1090ES. The PowerFLARM will "see"
airliner traffic today via PCAS but obviously not get direction
information and PCAS tends to operate at relatively short range for
the fast closure rates involved in a collison with an airliner or fast-
jet. In general it really is a bad idea to think gliders are going to
operate in areas of high-density airline or fast-jet traffic and rely
on PCAS or ADS-B receivers to help provide avoid mid-air collisions.
The closure rates are high, gliders are often invisible to ATC primary
radar, and gliders are incredibly hard to see for those flight crews
even if they are aware/expecting the glider traffic.

In the USA and Europe effectively all airliners, many fast-jets and
many military transpots etc. are TCAS equipped, and many of that is
TCAS II. TCAS II provides those flight crew with mandatory climb/
descent instruction to avoid collisions. These instructions must be
followed and override ATC instructions to the pilot. Flarm and
PowerFLARM do not provide any visibility to TCAS and a TCAS equipped
airliner or fast jet will plow right through a glider equipped with
Flarm or PowerFLARM with no warning. A Mode C or Mode S transponder
is the only device that both provide visibility to ATC radar and to
TCAS systems (and also TAS/TCAD and PCAS systems).

For all these reasons it is important for areas of high density
airline and fast-jet traffic that glider pilots continue to consider
equipping with transponders. It will will be concerning in those area
if say PowerFLARM is seen by some pilots as simple alternative to
transponder adaption.

The post also compares PCAS to Flarm. Many pilots in the USA use PCAS
for awareness of GA traffic and that is not addressed by traditional
Flarm units. The PowerFLARM is interesting in it does includes PCAS
capabilities.

The PCAS and 1090ES receiver capability of the PowerFLARM make it very
interesting to combine with a Mode S transponder with 1090ES data out
capability (like the Trig TT21) and that provides a solution that does
address a wide range of collision scenario. But in the USA even that
system will have issues at times inter-operating with UAT systems in
the dual-line ADS-B system in the USA (e.g. the issues with operating
outside of GBT coverage that I've described before in this thread).

---

I would also be careful claiming Flarm would prevent specific
accidents without a careful analysis. Especially because it is
unlikely that many GA aircraft will equip with a Flarm or PowerFLARM
device. So I'm not sure I claim absolutely that this would prevent the
Colorado mid-air with a Cirrus. PowerFLARM in the glider and tow plane
may have detected the Cirrus via PCAS, the Cirrus transponder may have
been interrogated enough to provide a PCAS alert but you have issues
of PCAS accuracy and false alarms especially if either or both the tow-
plane or glider have transponders. And I am not aware of what if any
traffic awareness system the Cirrus had on board. I not sure Flarm or
PowerFLARM are really relevant to the Hudson river collision, as those
aircraft are just not likely to equip with either product. It is more
likely in future that those aircraft would equip with GA oriented PCAS
or ADS-B data-out and data-in products, if they were both suitably
equipped in future then yes, hopefully that would reduce the chance
for such a collision. PCAS itself may be problematic is some areas
like this because of the high traffic density and high alarm rates.

Darryl

On Aug 11, 8:55*am, Westbender wrote:
On Aug 11, 10:41*am, Dave Nadler wrote:



On Aug 11, 11:27*am, Westbender wrote:

On Aug 11, 10:09*am, mattm wrote:

On Aug 11, 10:41*am, Westbender wrote:

Forgive me if this is a really dumb question. I don't know much about
transponder operation.

Is it a technical requirement for a transponder to only transmit when
it's been interrogated by a ping from a remote source? I'm just
wondering why transponders can't have a "timeout" mechanism built into
it where it will automatically report/transmit if it hasn't been
pinged in a certain amount of time. Something like a 30 second
timeout? Maybe user-selectable? For the folks who fly in remote areas,
wouldn't something like this help? Or is the transponder response of
no use without pairing it with a request (ping)?

That's the meaning of "transponder" -- it transmits a response (to a
radar paint), plus it includes additional information. *It goes back
to
WWII days when it was originally known as IFF -- Identify Friend or
Foe. *The detection methods based on transponder response depend
on the timing between when the primary pulse is seen and the response.
The larger the duration, the further from the transponder you are.

This is the point of the FLARM scheme -- all the units periodically
broadcast their status, so they are visible even when there is no
radar around.

-- Matt

When I read the "how it works" on the Zaon website, it says it reads
the response. It doesn't say anything about using the primary pulse in
it's process. Is that typical of PCAS systems?

This is where my question originates. It seems that the PCAS system
might not need the initial request from a radar to evaluate threats.
If so, then wouldn't an aircraft transponder "replying" without a
radar pulse give surrounding aircraft with PCAS the means to detect?

A PCAS system replies on someone else interrogating the
transponders. "Someone" is either a ground radar station or
a TCAS-II equipped aircraft. If you are in a valley without
radar and without overflying jets, you will hear nothing.

Hope that helps,
Best Regards, Dave- Hide quoted text -

- Show quoted text -

Right, did you read my first post?

Since the MRX PCAS (passive) only uses the reply from transponders,
wouldn't it be nice if the trig had a timed/scheduled transmit when
not interrogated for a certain amount of time? If so, a combination of
a trig/PCAS would be relatively inexpensive for glider-to-glider
detection (yeah, yeah, assuming everyone had that combo). The best
part would be the benefits of the "normal" operating mode of the trig
and PCAS in relation to other GA and commercial aircraft.

What are the ramifications of doing something such a thing?

I am not sure you want a bunch of transponders flying around sending
out what look like false replies to interrogations. And nobody is
going to be interested in trying to do this, there is no RTCA standard
for transponders to comply with that would allow this and nobody is
going to be interested in looking at this given the move to ADS-B.

The evolution of this thought process leads directly to ADS-B 1090ES
which is the automatic transmission of the aircraft position and other
data from the transponder without interrogation. Those transmissions
are clearly distinguishable from a conventional transponder
interrogation reply. A traditional PCAS unit will not decode the
threat altitude from that transmission and therefore not alert on the
threat.

Darryl

Thanks!

Just an attempt to think outside the box a little. I figured there had
to be a good reason it couldn't work. It's just too simple a
solution... )

On Aug 11, 9:44*am, Westbender wrote:
Thanks!

Just an attempt to think outside the box a little. I figured there had
to be a good reason it couldn't work. It's just too simple a
solution... *)

This is a question, not a proposal. Would pushing the IDENT button on
the transponder allow you to be seen by PCAS? I am really not
suggesting that we push the IDENT button every 20 seconds but I am
curious.

On Aug 11, 9:55*am, brianDG303 wrote:
On Aug 11, 9:44*am, Westbender wrote:

Thanks!

Just an attempt to think outside the box a little. I figured there had
to be a good reason it couldn't work. It's just too simple a
solution... *)

This is a question, not a proposal. Would pushing the IDENT button on
the transponder allow you to be seen by PCAS? I am really not
suggesting that we push the IDENT button every 20 seconds but I am
curious.

Nope. Pushing the ident buttons just changes slightly the reply the
transponder sends to some of the interrogations it receives. I adds
the "SPI" pulse at the end of all Mode A interrogation for ~19 seconds
after you push the ident button.

Do not go pushing that button without being told to by ATC (I've even
seen folklore where people thought you were supposed to always press
ident after changing transponder code). You may annoy your friendly
ATC guy.

Darryl

I fly in Worcester South Africa, and most of our fleet has been flarm
equipped soon after flarm came onto the market. Prior to that i lost
two very good friends (both very competent and experienced pilots) in
a mid-air. We have also had a number of mid-airs over the years in SA.
In Worcester we do some ridge flying and it really makes sense to use
flarm.
I have also flown with flarm in a number of international contests. My
latest experience has been Prievidza - most gliders were flarm
equipped - to the extent that one would even feel some mild iritation
if someone came close and there was no collision warning, as you
realised that glider was not flarm equipped. The algorithms are well
sorted now, and the collision warnings are for those you really need
the warning. Incidenlty the mid-air we did have on the first day was
been a non-flarm equipped glider and a flarm equipped glider. In a
sense i rest my case (I accept, of course, that it won't always help,
AND that you have to do all the things you are meant to do).
As some-one else has pointed out - flarm is a fully functional
solution for a very real problem (especially in contests).
It is also relatively inexpensive - it is also a logger and you can
run your pda from it (you can also link it to a voice system (such as
Triadis-DVS) or the butterlfy display.
Cynically i may say that i don't care whether you wear a parachute or
not, as my parachute will function irrespective of yours.
Flarm is different - it only works for me if you also have one.

Sven wrote:
I have also flown with flarm in a number of international contests. My
latest experience has been Prievidza - most gliders were flarm
equipped - to the extent that one would even feel some mild iritation
if someone came close and there was no collision warning, as you
realised that glider was not flarm equipped.

When I was flying on one of those "glider highways" in Europe, I once
heard a radio call: Attention to all, there's a non-FLARM-equipped
glider coming!

Brad Hill and I ordered a PowerFlarm each and that means we have
achieved 25% penetration of the core XC group from our field.

Brian

On Aug 11, 9:23*am, Darryl Ramm wrote:
On Aug 11, 8:07*am, William Gagen wrote:





FLARM - We NEED it yesterday.

How many more midairs do we need to have in our sport?

What if we have a midair with an airliner? Can you say soaring as a
sport is dead, as the FAA will reflexively eliminate all of our
flexibility.

The cost of FLARM in any form is negligible compared to staying
alive.

I have used FLARM at the IMGC Competition (International Military
Glider Comp) in Germany, and it turned a competition with 93 gliders
into the safest competition I have ever flown in anywhere.

It provides timely, accurate, important alerts for collision potential
with very few spurious or distracting warnings. It is vastly superior
to PCAS. There is absolutely no reason we shouldn't be requiring it
for all competition aircraft PERIOD!

The following midairs could all have been prevented by FLARM: Parowan
this summer, Uvalde this summer, Boulder last winter, the Hudson River
helicopter/light plane midair.

Thanks for reading my rant. But, having used it, I know how good it
is, and why we need it yesterday!

SSA could be helpful by providing loaner or rental FLARM units to
aircraft to use in competitions. In this way, we could get them into
every competition sooner. A pilot could rent a unit for say $100 a
competition, and over 2 summers the units would be paid off.

There is a gamut of collision scenarios from glider-glider, glider-
towplane, glider-GA, glider-fast-jet and glider-airliner and there is
no single technology or single product that well addresses all these
problems. The first thing in thinking about collision avoidance is to
be very clear just what problem(s) you are trying to solve.

I agree that Flarm and (and in the USA the flarm-flarm part of
PowerFLARM product) can be a significant help in glide-glider and
glider-towplane collision scenarios and I agree that the collision
with an airliner is a horrible scenario, for the innocent passengers
and crew, and would cause incredible damage to our sport. However
unfortunately this post seems to jumble up too much of all this
collision avoidance/traffic awareness technology and the capabilities
and benefits and that worries me.

The post talks about "flarm" helping with airliner collision avoidance
and that is a dangerous claim to make without some careful
qualification and is certainly not true with with the traditional
flarm product in Europe. Flarm (the flarm-flarm protocol) has nothing
to do with avoiding airliner collisions. Airliners and fast jets (and
most GA traffic outside of say tow planes) just will not be able to
receive or transmit the flarm protocol and the flarm protocol does not
make a glider visible to ATC.

The PowerFLARM product with 1090ES can receiver ADS-B over 1090ES.
Most airliners, fast jets and GA aircraft are not yet equipped with
1090ES data out. Rule for ADS-B equipage vary between Europe and the
USA, all airliners eventually will have 1090ES data-out but I don't
think anybody has good timelines yet for when a significant fraction
of them will be equipped. Once 1090ES data-out equipped a PowerFLARM
would "see" that traffic via 1090ES. The PowerFLARM will "see"
airliner traffic today via PCAS but obviously not get direction
information and PCAS tends to operate at relatively short range for
the fast closure rates involved in a collison with an airliner or fast-
jet. In general it really is a bad idea to think gliders are going to
operate in areas of high-density airline or fast-jet traffic and rely
on PCAS or ADS-B receivers to help provide avoid mid-air collisions.
The closure rates are high, gliders are often invisible to ATC primary
radar, and gliders are incredibly hard to see for those flight crews
even if they are aware/expecting the glider traffic.

In the USA and Europe effectively all airliners, many fast-jets and
many military transpots etc. are TCAS equipped, and many of that is
TCAS II. TCAS II provides those flight crew with mandatory climb/
descent instruction to avoid collisions. These instructions must be
followed and override ATC instructions to the pilot. Flarm and
PowerFLARM do not provide any visibility to TCAS and a TCAS equipped
airliner or fast jet will plow right through a glider equipped with
Flarm or PowerFLARM with no warning. *A Mode C or Mode S transponder
is the only device that both provide visibility to ATC radar and to
TCAS systems (and also TAS/TCAD and PCAS systems).

For all these reasons it is important for areas of high density
airline and fast-jet traffic that glider pilots continue to consider
equipping with transponders. It will will be concerning in those area
if say PowerFLARM is seen by some pilots as simple alternative to
transponder adaption.

The post also compares PCAS to Flarm. Many pilots in the USA use PCAS
for awareness of GA traffic and that is not addressed by traditional
Flarm units. The PowerFLARM is interesting in it does includes PCAS
capabilities.

The PCAS and 1090ES receiver capability of the PowerFLARM make it very
interesting to combine with a Mode S transponder with 1090ES data out
capability (like the Trig TT21) and that provides a solution that does
address a wide range of collision scenario. But in the USA even that
system will have issues at times inter-operating with UAT systems in
the dual-line ADS-B system in the USA (e.g. the issues with operating
outside of GBT coverage that I've described before in this thread).

---

I would also be careful claiming Flarm would prevent specific
accidents without a careful analysis. Especially because it is
unlikely that many GA aircraft will equip with a Flarm or PowerFLARM
device. So I'm not sure I claim absolutely that this would prevent the
Colorado mid-air with a Cirrus. PowerFLARM in the glider and tow plane
may have detected the Cirrus via PCAS, the Cirrus transponder may have
been interrogated enough to provide a PCAS alert but you have issues
of PCAS accuracy and false alarms especially if either or both the tow-
plane or glider have transponders. And I am not aware of what if any
traffic awareness system the Cirrus had on board. I not sure Flarm or
PowerFLARM are really relevant to the Hudson river collision, as those
aircraft are just not likely to equip with either product. It is more
likely in future that those aircraft would equip with GA oriented PCAS
or ADS-B data-out and data-in products, if they were both suitably
equipped in future then yes, hopefully that would reduce the chance
for such a collision. PCAS itself may be problematic is some areas
like this because of the high traffic density and high alarm rates.

Darryl- Hide quoted text -

- Show quoted text -

One thing to note for those already using a PCAS is that the
PowerFlarm can replace your PCAS unit, so you can save few hundred
bucks by selling your PCAS unit on Ebay. I am curious to know how the
PowerFlarm performs as a PCAS vs the ZAON MRX. While the MRX
definitely detects more aircrafts than our eyes, I often find the
audio alert does not give early enough warnings. Was any comparison
done between the units?

While I believe almost all of us (except maybe Mike) are sold on the
PowerFlarm, and I am definitely going to buy one, it will be good to
show some statistics of how effective the Flarm was so far in reducing
mid airs, in particular, if any midair occured between 2 gliders
equipped with operaional flarms.

Assuming the PowerFlarm will be available really soon (anyone knows
when?), and based on the feedbacks we heard so far from pilots using
it in contests, I can hardly imagine that anyone will want to fly in
a contest again without one after the chain of midairs we had
recently. I hope it will be mandatory, but to make it mandatory no
doubt the SSA should be able to rent them first, at least for the
first year or so, as I am sure everyone will want to buy one after
renting it once. At this rate I expect with some peer pressure most
pilots will be equiped with Flarms soon, those who don't will have
hard time sharing the sky with their buddies.

And last, I am not sure why the claim that GA pilots are not going to
adopt the PowerFlarm. They also suffer from midairs, and most of them
can efford it as well. I believe the ZAON MRX is quiet popular among
GA pilots as well, so I would expect the same to be true with
PowerFlarm which can replace the MRX and cost only $1K or so more.

Ramy