Flarm in the US

On Aug 11, 12:19*pm, Greg Arnold wrote:
On 8/11/2010 12:15 PM, Ramy wrote:



Maybe I got lost in details, but I don't see much difference (except
the thermaling specific algorithms) between our needs and GA needs, at
least the slower "low end" GA which does not already use more
sofisticated traffic alert equipment than PCAS. If it is the best
solution for us, why isn't it for them? If they buy PCAS, why wouldn't
they buy PowerFlarm?

PowerFlarm may have fancy software to try to take into account that
gliders often do not fly straight. *However, PowerFlarm certainly can
handle the simpler situation where planes do fly straight, and so I
would think Ramy is right -- PowerFlarm would be very useful to GA.

A couple of points, some restated..

The PowerFLARM does no support popular portable or fixed dispays used
in the GA market. That may be an issue for some pilots. That is also
something FLARM could address in future (with software and/or hardware
changes).

To have the flarm protocol be useful you have to have significant
adoption. And I just do not see why or how that would happen in the GA
market. I could see examples offered before of pockets of possible
interest (news/rescue helicopters, fire bombers/spotters, logging
helicopters).

To have the ADS-B part work you need an ADS-B transmitter. For the low-
end part of the GA market in the USA most likely to adopt ADS-B data-
out (voluntarily or to meet mandate requirements) typically have Mode
C transponders today. For those lower-end aircraft I expect UAT
devices as presumably they appear (and gain TSO approval) to be
appealing. It is not clear there will be a separate UAT transmitter
market. I expect to see transceivers and receivers.

For more modern aircraft with Mode S transponders I expect is more
likely for pilots to upgrade their Mode S to 1090ES data out and at
the low-end of that group the PowerFLARM as an add-on receiver could
be interesting if the issue of display compatibility does not matter.
But in that market of more modern GA aircraft you rapidly run into
cockpits where owners/pilots are more likely to want to deploy
something that integrates with their current display and other toys
even if not IFR certified. More complex cockpits also raise some
interesting questions of device compatibility (ability to correctly
set the capability code bits for ADS-B) that seem to be an open
question and it is not clear that all these GA modern glass panel
systems will necessarily be compatible with portable ADS-B receivers
(this is mostly a USA issue). ADS-B is a slow painful process so we
need to really see what happens. If a PowerFLARM was priced close to
an Zaon MRX then I'd say its a no-brainer for any low-end GA pilot to
adopt it. The PCAS feature in the PowerFLARM is a nice feature that
other 1090ES receivers are not providing but I'm sure that will sway
much of the GA market, esp. compared to display compatibility etc.

The USA market, with its dual-link and UAT options is a bit different
than Europe. Europe has mandatory Mode S transponders and is going
1090ES data-out only. And I expect the PowerFLARM to be relatively
more appealing to lower-end GA pilots there than in the USA. I am not
saying a GA pilot cannot or should not use a PowerFLARM I am trying to
point out that as the product looks today it may be a significantly
less compelling product in the USA GA market than some glider pilots
seem to be assuming. If Flarm/Butterfly want to target the USA GA
market there are some obvious things they could do in future. It is a
however a very compelling product for many of us now...


Darryl

What do you guys suspect the threat display would look like on the
Powerflarm for a non-flarm threat? A ring all the way around to show
range and an altitude differential? As opposed to the small triangles
showing location, direction and altitude differential?

Just curious. Anyone know?

On Aug 11, 12:05*pm, Darryl Ramm wrote:

It can't apply to PCAS (Mode C/S) because the PowerFLARM has no idea
of the direction of the threat,

Is that somewhere in the specs and I missed it. There is no reason a
passive tranponder detection system cannot be directional. It does
require a directional antenna system though. (ref Zaon XRX).

If position was only resolved to one of 4 quadrants though the
alerting could not be as good as for FLARM targets, but it could be
much better than the ZAON MRX that many of us are used to. Maybe an 8
sector directional antenna is being dreamed of. It could also be much
better than the MRX if a specific target (such as the tug) could be
tagged as "no threat". Even better if the "no threat tag" was
automatically cleared if there was a significant change in relative
altitude or direction of the tagged target. Maybe they are aware of
the fact that gliders may use a unique squawk that distinguishes them
from VFR aircraft and will provide different threat alerting.

Until there are some hard specs and real hardware with integrated and
functional software, PowerFLARM could just be a marketeers dream.

Somebody please say you have actually seen one working and shoot me
down.

Andy

From the LX website regarding the Powerflarm. See the first paragraph
and second bullet point in the summary.



Power Flarm is designed to give precise warning of the relative
positions of ADS-B transmitting aircraft and of aircraft transmitting
Flarm information. Its Mode-C warning gives both distance (accuracy
some 100m) and relative altitude (accuracy 25ft/50ft depending on
XPDR).

It utilizes the same warning technology and motion prediction used in
FLARM. This means it calculates hazard-levels as a function of many
parameters and not only distance. (Its algorithms continually
calculate and forecast possible flight vectors and matches them to
probabilities) Warnings are given visually and acoustically depending
on the severity of the hazard.

The display and user-interface is designed to minimize distraction.

In summary it detects:

•other ADS-B equipped aircraft without PowerFLARM
•other Mode-C/S XPDR equipped aircraft ( range but not direction)
•other aircraft with normal FLARM compatible systems

And all the time it transmits its own Flarm data making you
conspicuous to other Flarm equipped aircraft

I would think it can still calculate whether a target is converging or
not (range/altitude differential). Wouldn't it need multiple xpndr
replies identifying the same target? I would guess such a thing would
be pretty difficult in a gaggle though.

I have sent an email inquiring about just how the different sources
are dealt with in terms of predicting threats. Hopefully they'll
respond.

On Aug 11, 1:32*pm, Andy wrote:
On Aug 11, 12:05*pm, Darryl Ramm wrote:

It can't apply to PCAS (Mode C/S) because the PowerFLARM has no idea
of the direction of the threat,

Is that somewhere in the specs and I missed it. *There is no reason a
passive tranponder detection system cannot be directional. *It does
require a directional antenna system though. (ref *Zaon XRX).

If position was only resolved to one of 4 quadrants though the
alerting could not be as good as for FLARM targets, but it could be
much better than the ZAON MRX that many of us are used to. *Maybe an 8
sector directional antenna is being dreamed of. *It could also be much
better than the MRX if a specific target (such as the tug) could be
tagged as "no threat". *Even better if the "no threat tag" was
automatically cleared if there was a significant change in relative
altitude or direction of the tagged target. Maybe they are aware of
the fact that gliders may use a unique squawk that distinguishes them
from VFR aircraft and will provide different threat alerting.

Until there are some hard specs and real hardware with integrated and
functional software, PowerFLARM could just be a marketeers dream.

Somebody please say you have actually seen one working and shoot me
down.

Andy

The PowerFLARM definitely does not have a directional 1090MHz
antenna.

Chasing directional PCAS type things like the XRX is likely a waste of
time given ADS-B's arrival. I don't expect to see any other of these
directional PCAS systems from any vendors.


Darryl

On Aug 11, 1:58*pm, Westbender wrote:
I would think it can still calculate whether a target is converging or
not (range/altitude differential). Wouldn't it need multiple xpndr
replies identifying the same target? I would guess such a thing would
be pretty difficult in a gaggle though.

I have sent an email inquiring about just how the different sources
are dealt with in terms of predicting threats. Hopefully they'll
respond.

Those of us who fly say with a Zaon MRX seem to be pretty impressed
with its ability to give you a heads up of traffic but PCAS is
inherently so imprecise that to talk about it in the same sentence as
the high precision FLARM protocol is kind of a stretch. But I think
the idea of including PCAS in the PowerFLARM is very good.

In a crowded gaggle of gliders equipped with Mode C transponders your
PCAS unit will likely just not work in a useful way. There will be
substantial overlap of replies from transponders in the Gaggle, an
effect called syncronous garbling. If the gliders in the Gaggle have
Mode S transponders and are being interrogated by a Mode S
interrogator (like most radar and TCAS units) this effect will be
greatly minimized. Good receivers can handle some partial overlap but
a crowded gaggle of Mode C transponders is going to throw your PCAS
for a real loop. It is this sort of reason that I know PCAS cannot
reliably work and why I expect the PowerFLARM to have a way to just
turn down the PCAS alert. Its just such an obvious thing, and given
how smart the Flarm guys seem to be not something I am worried about.

In many remote areas (like where many glider contests are held?) the
interrogation rates may be low (typical SSR radar interrogate in a
burst ever 5 or 12 second rotation). You may get more rapid
interrogations for overflying aircraft TCAS etc.

All it might take for a threat aircraft is a slight change in relative
antenna orientation and the threat may appear closer. Think of two
gliders thermalling in different thermals near each other--with the
received power of their transponder signals jumping all over the
place. This is just not a foundation on which you can do much more
than beep when another threat appears to be with several miles and
some altitude window. The transmitted encoder altitude is really the
only thing you know reliably, and even that can have issues with Mode
A and Mode C signal aliasing (I'm surprised most PCAS units work as
well as they do).

Alright now I'm really beyond fed up listening to myself.

Darryl

On Aug 11, 4:51*pm, Darryl Ramm wrote:
On Aug 11, 1:58*pm, Westbender wrote:

I would think it can still calculate whether a target is converging or
not (range/altitude differential). Wouldn't it need multiple xpndr
replies identifying the same target? I would guess such a thing would
be pretty difficult in a gaggle though.

I have sent an email inquiring about just how the different sources
are dealt with in terms of predicting threats. Hopefully they'll
respond.

Those of us who fly say with a Zaon MRX seem to be pretty impressed
with its ability to give you a heads up of traffic but PCAS is
inherently so imprecise that to talk about it in the same sentence as
the high precision FLARM protocol is kind of a stretch. But I think
the idea of including PCAS in the PowerFLARM is very good.

In a crowded gaggle of gliders equipped with Mode C transponders your
PCAS unit will likely just not work in a useful way. There will be
substantial overlap of replies from transponders in the Gaggle, an
effect called syncronous garbling. If the gliders in the Gaggle have
Mode S transponders and are being interrogated by a Mode S
interrogator (like most radar and TCAS units) this effect will be
greatly minimized. Good receivers can handle some partial overlap but
a crowded gaggle of Mode C transponders is going to throw your PCAS
for a real loop. It is this sort of reason that I know PCAS cannot
reliably work and why I expect the PowerFLARM to have a way to just
turn down the PCAS alert. Its just such an obvious thing, and given
how smart the Flarm guys seem to be not something I am worried about.

In many remote areas (like where many glider contests are held?) the
interrogation rates may be low (typical SSR radar interrogate in a
burst ever 5 or 12 second rotation). You may get more rapid
interrogations for overflying aircraft TCAS etc.

All it might take for a threat aircraft is a slight change in relative
antenna orientation and the threat may appear closer. Think of two
gliders thermalling in different thermals near each other--with the
received power of their transponder signals jumping all over the
place. This is just not a foundation on which you can do much more
than beep when another threat appears to be with several miles and
some altitude window. The transmitted encoder altitude is really the
only thing you know reliably, and even that can have issues with Mode
A and Mode C signal aliasing (I'm surprised most PCAS units work as
well as they do).

Alright now I'm really beyond fed up listening to myself.

Darryl

Thanks Darryl, I really appreciate the info.

On 8/11/2010 12:19 PM, Greg Arnold wrote:
On 8/11/2010 12:15 PM, Ramy wrote:


Maybe I got lost in details, but I don't see much difference (except
the thermaling specific algorithms) between our needs and GA needs, at
least the slower "low end" GA which does not already use more
sofisticated traffic alert equipment than PCAS. If it is the best
solution for us, why isn't it for them? If they buy PCAS, why wouldn't
they buy PowerFlarm?


PowerFlarm may have fancy software to try to take into account that
gliders often do not fly straight. However, PowerFlarm certainly can
handle the simpler situation where planes do fly straight, and so I
would think Ramy is right -- PowerFlarm would be very useful to GA.
Do we have any idea of the percentage of GA using a PCAS like the MRX?
I'm of the impression it's a small percentage, smaller than the
percentage of gliders equipped with PCAS. I suspect a lot of power
pilots think they have the collision situation covered with their
transponder and Flight Following. A few that fly where there are a lot
of gliders, like the Reno area, might be interested in a Flarm unit.

--
Eric Greenwell - Washington State, USA (netto to net to email me)

- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm http://tinyurl.com/yb3xywl

- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz

On 8/11/2010 11:28 AM, Andrzej Kobus wrote:
Let's take a real life example. Last year I flew in Sports Nationals
in Elmira. I had PCAS with me. The first day after I released and
started climbing with a bunch of other gliders many of them equipped
with transponders I had to switch my PCAS off because of the quantity
of warnings. It was useless in that scenario.

Did you turn off the power, or just press the "mute" button? I've muted
mine when circling with another transponder-equipped glider so the audio
didn't annoy me, but the display continued to show the altitude
difference. That seemed useful to me.

--
Eric Greenwell - Washington State, USA (netto to net to email me)

- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm http://tinyurl.com/yb3xywl

- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz