Flarm in the US this summer

ADS-B transceivers do not include any collission avoidance logic. They
purely send and receive aircraft type information along with possition and
velocity vector information.

Traffic information that is received by an ADS-B transeiver, either from
another ADS-B transmitter or from an ADS-B ground station is passed to
whatever display device the user wants to interface to the unit. This can
be another GPS display, an IPAQ running a navigation program like See You
Mobile, or even an iPhone running a custom app to display aircraft possition
data.

There is nothing stopping anyone from developing the same or more
sophisticated traffic warning logic in these attached devices that are
currently available with FLARM. Personally, I believe that an audio alert
that gives you traffic warnings relative to your current heading and
altitude (i.e. "Traffic closing at 100 knots, 1/2 mile 3 o'clock, 100 ft low
and climbing") would be very useful for glider applications. I can imagine
that software vendors would add these functions to their offerings, or
someone could start an open source software effort to develop these types of
applications. Once the raw data is available, and ADS-B units are being
deployed in volume, inovation in this area is bound to be very rapid.

Mike Schumann

"johngalloway" wrote in message
...
I think that it helps to think of Flarm as being the algorithm and
radio transmission protocol and not the hardware. The unique feature
of Flarm is that it broadcasts predictions of a glider's flight path
based on the characteristics of glider flight (i.e including a lot of
turning and circling flight) and compares its own prediction with
those of the other received broadcasts. Given the agreed close
proximity of a lot of glider flying (eg circuits, thermalling, ridge
soaring, cruising on shared task etc) then without a proven and
common glider specific predictive algorithm any hardware technology
would be unusable for inter-glider collision avoidance because of
excessive alerts generated by proximities and paths that would be
unacceptable to general and commercial aviation.

If a transponder or ADSB equipment manufacturer wanted to make his
product useful for glider/glider or glider/low speed power collision
avoidance than he would need to include glider specific predictive
algorithm. He could then either license and use the proprietary and
proven Flarm algorithm or develop another one. The latter course
would have the 3 serious disadvantages of significant extra
development costs, development time delay, and a reduction of
performance as different algorithms in different gliders might result
in one glider pilot receiving a collision alert the other not.

The obvious way forward for transpdonder/ADSB manufacturers is that
which is being developed in Europe i.e. a common display that will
show inputs from Flarm units and transponder/ADSB.

Flarm functionality is already included in numerous other products
(varios and data recorders) and there is no reason why it should not
be included in future US or European transponder or ADSB boxes if the
market were sufficient.

Ergo the whole discussion based on the idea that Flarm and ADSB are
alternatives to one another is based on a misconception that, I have
to say, persists in the minds of many UK as well as US glider pilots.

John Galloway

( co-author of the 2007 Scottish Gliding Union Flarm trial report:
http://www.flarm.com/news/SGU_Flarm_Report.pdf )

On Jul 24, 3:05*am, "Mike Schumann" mike-nos...@traditions-
nospam.com wrote:
[snip] There is nothing stopping anyone from developing the same or
more
sophisticated traffic warning logic in these attached devices

AIUI, Flarm broadcasts the projected path of its host glider. I think
it recognises the difference betaween thermalling (circles) and
cruising.

Would "these attached devices" be able to transmit that?

Similarly, a Flarm receiving such broadcasts compares them with its
host glider predicted path, and alerts if collision likely, and if not
simply displays what is the nearst unit.

[snip] " . . . I believe that an audio alert that gives you traffic
warnings relative to your current heading and altitude (i.e. "Traffic
closing at 100 knots, 1/2 mile 3 o'clock, 100 ft low and climbing")
would be very useful for glider applications."

Flarm gives indications relative to track, not heading. It does not
know which way the glider is pointing, it only knows the history of
its GPS positions. Mostly this is not a big difference, but ridge or
wave soaring in strong winds make a huge diference. I expect many
pilots have experienced track at almost 90 degrees to heading, and
even 180 degrees in high wave (i.e. flying too slowly! - I certainly
have). I am told, by people who use Flarm in these conditions, that
you get used to the indications being relative to track.(I have had my
Flarm for too short a time to yet experience this.)

What sort of device would be able to indicate relative to heading? Is
anyone going to develop such a device?

On the general point, I have been engaged in dialogue and
correspondence in the UK about Flarm and PCAS. My own conclusions are
that:

In some places, glider-glider (or glider-tug) collisons are far more
likely than glider-unrelated power. For those, if you can only fit
one, fit Flarm. In the UK that is true for almost all gliding clubs.
Most UK glider-glider collisons are over or close to the gliding site
they both took off from. Therefore, it does not take the whole country
fitting them to provide a benefit for the individual pilot - if all
your mates have them, they are the most likely ones for you to collide
with, so it helps with the biggest scenario of risk you have. It could
be beneficially done club by club.

There may be places where glider-unrelated power collisions are a
significant risk. For those, if the unrelated power is likely to have
a transponder, then PCAS provides a degree of assistance. You don't
need a transponder yourself, if you can detect a threat and take
avoiding actions. I don't know about the USA, but in the UK, 3 of the
5 such collisions over the last 39 years were also near or immediately
over the gliding site of the gliding participant. They are also more
likely to incur fatalities - 6 people died in the 5 UK collisions. Too
many winch launch sites have overflights of unrelated powered
aircraft, at or below winch launch heights, and they are sometimes
seen too late by ground crews when a winch launch is taking place -
one of the 5 UK collisions killed two glider pilots while winch
launching. So I think such sites would benefit from having a PCAS on
the ground, at the launch point, too. Mine, when on the ground, has
alerted an overflying airctaft, and has indicated the presence of
approaching ones long before the eye can pick them up.

So if you can afford two units, and the glider can accommodate them, I
think Flarm + PCAS is becoming the best answer. Yes, it needs Flarm to
be widely adopted - but as I said, that can be on a club-by-club
basis.

There may be places where a glider really needs, or at least can
benefit from, having a transponder too. I gather that applies in parts
of the USA. It is not very obvious than it would help most UK glider
pilots to any great extent, but I would have fitted one by now if I
could. Unfortunately, the EASA regulatory regime under which most UK
gliders now operate prevents many, including mine, easily, legally, or
economically doing it. (I am not going to get into the details here -
believe it or not as you wish, but it is a fact.)

I think everybody realises that transponders alone provide no
anticollision protection. They only do so if combined with one or more
of: ATC providing a radar service; TCAS; and/or PCAS or similar. In
the USA, perhaps you can always get radar service, maybe glider pilots
tolerate the workload it takes, and use ATC frequencies instead of
dedicated gliding channels. That is certainly not the case in the UK,
except in a few places where using ATC really helps. Most of us, most
of the time, keep away from airspace where ATC has to be contacted,
and use the radio if at all only on gliding channels.

In the long term, ADS-B may provide a solution that make everything
interoperable with everything else. I suspect that is 10 or more years
away. meanwhile, I would like to see a significant reduction in the
annual death toll of colliding glider pilots. I particularly don't
want to be a statistic myself, while waiting for the dream solution.
So I bought Flarm and PCAS. I think that wowuld bring big benefits to
most glider pilots. If only one, choose the one that addresses the
risk you most encounter, based on accident figures for the sort of
place you mostly fly. (Does anybody have the USA data for glider
collisions, how many and what sort of place?) If you can afford, and
the glider can accommodate, all three, then go for the transponder
too.

IMHO.

Chris N.

On Jul 24, 3:05 am, "Mike Schumann"
mike-nos...@traditions- nospam.com wrote:


[snip] There is nothing stopping anyone from developing the same or
more
sophisticated traffic warning logic in these attached devices


AIUI, Flarm broadcasts the projected path of its host glider. I think
it recognises the difference between thermalling (circles) and
cruising.

Would "these attached devices" be able to transmit that?


Similarly, a Flarm receiving such broadcasts compares them with its
host glider predicted path, and alerts if collision likely, and if not
simply displays what is the nearest unit.


[snip] " . . . I believe that an audio alert that gives you traffic
warnings relative to your current heading and altitude (i.e. "Traffic
closing at 100 knots, 1/2 mile 3 o'clock, 100 ft low and climbing")
would be very useful for glider applications."


Flarm gives indications relative to track, not heading. It does not
know which way the glider is pointing; it only knows the history of
its GPS positions. Mostly this is not a big difference, but ridge or
wave soaring in strong winds make a huge difference. I expect many
pilots have experienced track at almost 90 degrees to heading, and
even 180 degrees in high wave (i.e. flying too slowly! - I certainly
have). I am told, by people who use Flarm in these conditions, that
you get used to the indications being relative to track.(I have had my
Flarm for too short a time to yet experience this.)


What sort of device would be able to indicate relative to heading? Is
anyone going to develop such a device?


On the general point, I have been engaged in dialogue and
correspondence in the UK about Flarm and PCAS. My own conclusions are
that:


In some places, glider-glider (or glider-tug) collisions are far more
likely than glider-unrelated power. For those, if you can only fit
one, fit Flarm. In the UK that is true for almost all gliding clubs.
Most UK glider-glider collisions are over or close to the gliding site
they both took off from. Therefore, it does not take the whole country
fitting them to provide a benefit for the individual pilot - if all
your mates have them, they are the most likely ones for you to collide
with, so it helps with the biggest scenario of risk you have. It could
be beneficially done club by club.


There may be places where glider-unrelated power collisions are a
significant risk. For those, if the unrelated power is likely to have
a transponder, then PCAS provides a degree of assistance. You don't
need a transponder yourself, if you can detect a threat and take
avoiding actions. I don't know about the USA, but in the UK, 3 of the
5 such collisions over the last 39 years were also near or immediately
over the gliding site of the gliding participant. They are also more
likely to incur fatalities - 6 people died in the 5 UK collisions. Too
many winch launch sites have overflights of unrelated powered
aircraft, at or below winch launch heights, and they are sometimes
seen too late by ground crews when a winch launch is taking place -
one of the 5 UK collisions killed two glider pilots while winch
launching. So I think such sites would benefit from having a PCAS on
the ground, at the launch point, too. Mine, when on the ground, has
alerted an overflying aircraft, and has indicated the presence of
approaching ones long before the eye can pick them up.


So if you can afford two units, and the glider can accommodate them, I
think Flarm + PCAS is becoming the best answer. Yes, it needs Flarm to
be widely adopted - but as I said, that can be on a club-by-club
basis.


There may be places where a glider really needs, or at least can
benefit from, having a transponder too. I gather that applies in parts
of the USA. It is not very obvious than it would help most UK glider
pilots to any great extent, but I would have fitted one by now if I
could. Unfortunately, the EASA regulatory regime under which most UK
gliders now operate prevents many, including mine, easily, legally, or
economically doing it. (I am not going to get into the details here -
believe it or not as you wish, but it is a fact.)


I think everybody realises that transponders alone provide no anti-
collision protection. They only do so if combined with one or more of:
ATC providing a radar service; TCAS; and/or PCAS or similar. In the
USA, perhaps you can always get radar service, maybe glider pilots
tolerate the workload it takes, and use ATC frequencies instead of
dedicated gliding channels. That is certainly not the case in the UK,
except in a few places where using ATC really helps. Most of us, most
of the time, keep away from airspace where ATC has to be contacted,
and use the radio if at all only on gliding channels.



In the long term, ADS-B may provide a solution that makes everything
interoperable with everything else. I suspect that is 10 or more years
away. Meanwhile, I would like to see a significant reduction in the
annual death toll of colliding glider pilots. I particularly don't
want to be a statistic myself, while waiting for the dream solution.
So I bought Flarm and PCAS. I think that would bring big benefits to
most glider pilots. If only one, choose the one that addresses the
risk you most encounter, based on accident figures for the sort of
place you mostly fly. (Does anybody have the USA data for glider
collisions, how many and what sort of place?) If you can afford, and
the glider can accommodate, all three, then go for the transponder
too.


IMHO.


Chris N.

My comments about FLARM vs ADS-B only apply to the US. Obviously in Europe,
where FLARM is very entrenched, the situation is very different.

ADS-B not only transmits the current aircraft position, but also the
aircraft type and the velocity vectors. Like FLARM, the basic ADS-B UAT
boxes like what MITRE has developed have built in GPS units and do not know
the pilot's intent. As a result the 3D velocity vector is derived from what
the aircraft is doing at the time of the transmission (which is updated each
second). More sophisticated ADS-B boxes used on airlines may transmit more
accurate velocity vectors using data received from Flight Management
Systems.

Whatever box is attached to the ADS-B transceiver is responsible for
interpreting the traffic data that is received. On advantage is that the
receiver knows what kind of aircraft is being observed. Power aircraft tend
to go in straight lines. Gliders are completely unpredictable. As a
result, you can design collision detection algorithms that are smart about
ignoring threats that are of minor consequence.

At the AOPA Expo in San Diego, MITRE demonstrated their low cost ADS-B UAT
transceiver hooked up to an iPhone to display traffic data. The latest
iPhone 3G has a compass capability built in. Using this functionality, you
could develop a collision detection program that actually identifies threats
by heading, not track. My personal feeling is that this would be incredibly
useful in a glider, particularly while you are circling in a thermal.

One of the really nice things about ADS-B is that the display / collision
detection function is separate from the actual transceiver. This provides
the potential for innovative software solutions, either as commercial
products, or as open source collaborative development efforts. Note: This
is obviously only applicable to VFR applications. Any equipment like this
for IFR use would be subject to FAA certification standards.

Mike Schumann


"Chris Nicholas" wrote in message
...
On Jul 24, 3:05 am, "Mike Schumann" mike-nos...@traditions-
nospam.com wrote:
[snip] There is nothing stopping anyone from developing the same or
more
sophisticated traffic warning logic in these attached devices

AIUI, Flarm broadcasts the projected path of its host glider. I think
it recognises the difference betaween thermalling (circles) and
cruising.

Would "these attached devices" be able to transmit that?

Similarly, a Flarm receiving such broadcasts compares them with its
host glider predicted path, and alerts if collision likely, and if not
simply displays what is the nearst unit.

[snip] " . . . I believe that an audio alert that gives you traffic
warnings relative to your current heading and altitude (i.e. "Traffic
closing at 100 knots, 1/2 mile 3 o'clock, 100 ft low and climbing")
would be very useful for glider applications."

Flarm gives indications relative to track, not heading. It does not
know which way the glider is pointing, it only knows the history of
its GPS positions. Mostly this is not a big difference, but ridge or
wave soaring in strong winds make a huge diference. I expect many
pilots have experienced track at almost 90 degrees to heading, and
even 180 degrees in high wave (i.e. flying too slowly! - I certainly
have). I am told, by people who use Flarm in these conditions, that
you get used to the indications being relative to track.(I have had my
Flarm for too short a time to yet experience this.)

What sort of device would be able to indicate relative to heading? Is
anyone going to develop such a device?

On the general point, I have been engaged in dialogue and
correspondence in the UK about Flarm and PCAS. My own conclusions are
that:

In some places, glider-glider (or glider-tug) collisons are far more
likely than glider-unrelated power. For those, if you can only fit
one, fit Flarm. In the UK that is true for almost all gliding clubs.
Most UK glider-glider collisons are over or close to the gliding site
they both took off from. Therefore, it does not take the whole country
fitting them to provide a benefit for the individual pilot - if all
your mates have them, they are the most likely ones for you to collide
with, so it helps with the biggest scenario of risk you have. It could
be beneficially done club by club.

There may be places where glider-unrelated power collisions are a
significant risk. For those, if the unrelated power is likely to have
a transponder, then PCAS provides a degree of assistance. You don't
need a transponder yourself, if you can detect a threat and take
avoiding actions. I don't know about the USA, but in the UK, 3 of the
5 such collisions over the last 39 years were also near or immediately
over the gliding site of the gliding participant. They are also more
likely to incur fatalities - 6 people died in the 5 UK collisions. Too
many winch launch sites have overflights of unrelated powered
aircraft, at or below winch launch heights, and they are sometimes
seen too late by ground crews when a winch launch is taking place -
one of the 5 UK collisions killed two glider pilots while winch
launching. So I think such sites would benefit from having a PCAS on
the ground, at the launch point, too. Mine, when on the ground, has
alerted an overflying airctaft, and has indicated the presence of
approaching ones long before the eye can pick them up.

So if you can afford two units, and the glider can accommodate them, I
think Flarm + PCAS is becoming the best answer. Yes, it needs Flarm to
be widely adopted - but as I said, that can be on a club-by-club
basis.

There may be places where a glider really needs, or at least can
benefit from, having a transponder too. I gather that applies in parts
of the USA. It is not very obvious than it would help most UK glider
pilots to any great extent, but I would have fitted one by now if I
could. Unfortunately, the EASA regulatory regime under which most UK
gliders now operate prevents many, including mine, easily, legally, or
economically doing it. (I am not going to get into the details here -
believe it or not as you wish, but it is a fact.)

I think everybody realises that transponders alone provide no
anticollision protection. They only do so if combined with one or more
of: ATC providing a radar service; TCAS; and/or PCAS or similar. In
the USA, perhaps you can always get radar service, maybe glider pilots
tolerate the workload it takes, and use ATC frequencies instead of
dedicated gliding channels. That is certainly not the case in the UK,
except in a few places where using ATC really helps. Most of us, most
of the time, keep away from airspace where ATC has to be contacted,
and use the radio if at all only on gliding channels.

In the long term, ADS-B may provide a solution that make everything
interoperable with everything else. I suspect that is 10 or more years
away. meanwhile, I would like to see a significant reduction in the
annual death toll of colliding glider pilots. I particularly don't
want to be a statistic myself, while waiting for the dream solution.
So I bought Flarm and PCAS. I think that wowuld bring big benefits to
most glider pilots. If only one, choose the one that addresses the
risk you most encounter, based on accident figures for the sort of
place you mostly fly. (Does anybody have the USA data for glider
collisions, how many and what sort of place?) If you can afford, and
the glider can accommodate, all three, then go for the transponder
too.

IMHO.

Chris N.

Mike, thanks. That is interesting stuff about ADS-B.

It is, of course, up to you guys in the USA to choose whatever is best
in the meantime. I still think that a wise choice should depend upon
the risk data, and I don’t see anybody answering the question about
the USA data for glider collisions, how many and what sort of place.

Until we looked at the UK accident reports over a long period, some
people had thought that cloud street running was likely to feature
prominently in our collisions. Turned out not so – not a single such
collision. As I wrote above, most are over or near the home site of
the gliding operators (glider, tug, motor glider). Some were in the
circuit (pattern, I believe, in US terminology), some thermalling. A
very small number were elsewhere, thermalling.

Chris N.

On Thu, 23 Jul 2009 05:49:39 -0700 (PDT), jcarlyle
wrote:

Perhaps Flarm
and Zaon should get together and discuss building a single, small
device that detects Flarm mode, A/C/S transponder modes, and ADS-B
mode?

Zaon is not involved, AFAIK, but you're looking for what's called a
"PowerFlarm". You can upgrade your existing Flarm unit with a
"bluebox" and a display, or buy the PowerFlarm.
I suspect it only works with ModeS xpdrs, not mode a/c.

Aldo


-John

Hi, Aldo,

Thanks for posting this. I checked the site for details (
http://www.powerflarm.com/details.html ), and ran it though Babelfish
so I could get the gist of it. It does seem to claim to only detect
Mode S, as you say. I'd think that this means that it's parsing
extended squitter position information only, and not parsing TIS-B
(Traffic Information Service - Broadcast), because then they'd also
get Mode C transponder data. Unfortunately, where I fly I'd need TIS-B
to see all the General Aviation aircraft, so for now I'll stick to a
transponder and PCAS.

-John

On Jul 25, 7:30 am, cernauta wrote:
Zaon is not involved, AFAIK, but you're looking for what's called a
"PowerFlarm". You can upgrade your existing Flarm unit with a
"bluebox" and a display, or buy the PowerFlarm.
I suspect it only works with ModeS xpdrs, not mode a/c.

Aldo



-John

On Jul 25, 10:22*am, jcarlyle wrote:
Hi, Aldo,

Thanks for posting this. I checked the site for details (http://www.powerflarm.com/details.html), and ran it though Babelfish
so I could get the gist of it. It does seem to claim to only detect
Mode S, as you say. I'd think that this means that it's parsing
extended squitter position information only, and not parsing TIS-B
(Traffic Information Service - Broadcast), because then they'd also
get Mode C transponder data. Unfortunately, where I fly I'd need TIS-B
to see all the General Aviation aircraft, so for now I'll stick to a
transponder and PCAS.

-John

On Jul 25, 7:30 am, cernauta wrote:

Zaon is not involved, AFAIK, but you're looking for what's called a
"PowerFlarm". You can upgrade your existing Flarm unit with a
"bluebox" and a display, or buy the PowerFlarm.
I suspect it only works with ModeS xpdrs, not mode a/c.

Aldo

-John

You will likely need TIS-B as mentioned, and in the USA ADS-R (to
relay UAT based devices to 1090ES). As pointed out before in other
threads the ADS-B ground stations rely on knowledge of the ADS-B
devices in the aircraft to determine what traffic information to
transmit, so receive only ADS-B devices may have problems. Those
problems might be mitigated if the PowerFlarm was used in an aircraft
equipped with a Mode-S transponder with 1090ES (that stack of Mode-S
transponder, GPS to feed the 1090ES and PowerFlarm would currently be
~US$10k). It seems the PowerFlarm only detects ADS-B over 1090ES and
not the actual transponder with a PCAS like approach so the bulk of
Mode-S transponders (all those new Gamins' etc.) in the USA fleet
that might support 1090ES expansion but don't yet actually talk 1090ES
will be invisible.

I think Flarm offers some useful benefits and could be useful in
places where we have opposing traffic on mountain ridges etc. but I
also fly in areas where we have intense airline and fast jet traffic
and in those areas (like around Reno) we need gliders to adopt Mode-C
or Mode-S transponders today, and specifically for Reno to communicate
with ATC (there are procedures developed by glider pilots with Reno
TRACON to help do this). That type of traffic density/conflict is
pretty unusual and needs elsewhere will be quite different.

Outside of that I think in general that long term traffic awareness
systems will be based on ADS-B technology. Longer term, what is
available to glider pilots in the USA will be driven by wider market
dynamics in the GA and experimental aircraft market, companies like
Zaon will have to deliver those ADS-B based products (or go out of
business). Still it may be interesting and useful to see Flarm
technology added to those devices (like the PowerFlarm unit mentioned
above is starting to do - even if its current ADS-B capabilities may
have too many issues esp. the USA market).


Darryl