Is FLARM helpful?

On Wednesday, November 25, 2015 at 1:29:44 PM UTC-8, jfitch wrote:

From this I conclude that the situational awareness, far away from an potential conflict, is more valuable for preventing potential conflicts in the first place than the actual warning facility.


Important observation. Pilots who fly in the thermal streets and convergence lines of the western US point this out pretty regularly. Head-to-head traffic at 17,999' can easily close at 5-6 statute miles per minute. In this case particularly (low-contrast, small head-on cross-section, potential for evasion maneuvers to make things worse with crossed wings) longer range situational awareness is critical to avoiding conflicts - often with a simple radio call to coordinate. Also a good reason to register with FarmNet - how many people really would be able to properly read and call out (or even recognize) an ICAO/Flarm ID in a time-constrained conflict situation? "AA8E2F, please turn right immediately!"

9B

On Wednesday, November 25, 2015 at 3:39:17 PM UTC-8, Andy Blackburn wrote:
On Wednesday, November 25, 2015 at 1:29:44 PM UTC-8, jfitch wrote:

From this I conclude that the situational awareness, far away from an potential conflict, is more valuable for preventing potential conflicts in the first place than the actual warning facility.


Important observation. Pilots who fly in the thermal streets and convergence lines of the western US point this out pretty regularly. Head-to-head traffic at 17,999' can easily close at 5-6 statute miles per minute. In this case particularly (low-contrast, small head-on cross-section, potential for evasion maneuvers to make things worse with crossed wings) longer range situational awareness is critical to avoiding conflicts - often with a simple radio call to coordinate. Also a good reason to register with FarmNet - how many people really would be able to properly read and call out (or even recognize) an ICAO/Flarm ID in a time-constrained conflict situation? "AA8E2F, please turn right immediately!"

9B

I have also observed this situation many times in the Nephi OLC camps and contests. High closure rates and Configuring your PowerFlarm in the Stealth mode would make this situation a safety concern. It would limit the time to respond to a conflict situation. With the Stealth mode off these situation are visible for many miles and evasive action is easy.

Stealth mode on this situation is much more immediate and dangerous with little time to identify, find and respond to the threat.


Richard
www.craggyaero.com

At 21:29 25 November 2015, jfitch wrote:
I am curious about your experience with the interface. Did you just have
the BF display, or was the Flarm also displaying targets on a moving
map?

I have not had any Flarm warnings that would have saved a midair (3
years
with it now). But I have always had Flarm targets displayed on the glide
computer moving map, and so nearly always see them long before they
could be
considered a threat. Two times in those three years I have gotten an
unexpected warning, though not close enough to require action to avoid
collision.
I use those events as a learning experience to see how I need to change
my
scans and operations, so that they do not happen again.

From this I conclude that the situational awareness, far away from an
potential conflict, is more valuable for preventing potential conflicts in

the
first place than the actual warning facility.=20

Countless times that Flarm has identified and displayed glider within a
km
of me that I had not seen and might never have seen.

I have used only the 'butterfly' display. To be clear, of course I am
seeing target alerts all the time. That is not a problem, and even
occasionally interesting (such as when someone starts following).
The problem is with false collision warnings. Many pilots appear to (and
some of my pupils certainly do) find it almost impossible to resist turning

away from the Flarm direction of the 'threat', before they have seen the
target. That is dangerous, as I wrote in a post yesterday. And note that
the Flarm direction is often significantly different from the true
direction
(occasionally diametrically opposite), as it is track-based, not heading-
based.

I can see that my experience of Flarm in a very busy environment (the
French Alps) will be very different from that of those flying largely in
isolation (such as flatlands, particularly with what I would regard as high

cloudbases (I'm a Brit!))
J.

On Thursday, November 26, 2015 at 2:45:07 PM UTC-8, James Metcalfe wrote:
At 21:29 25 November 2015, jfitch wrote:
I am curious about your experience with the interface. Did you just have
the BF display, or was the Flarm also displaying targets on a moving
map?

I have not had any Flarm warnings that would have saved a midair (3
years
with it now). But I have always had Flarm targets displayed on the glide
computer moving map, and so nearly always see them long before they
could be
considered a threat. Two times in those three years I have gotten an
unexpected warning, though not close enough to require action to avoid
collision.
I use those events as a learning experience to see how I need to change
my
scans and operations, so that they do not happen again.

From this I conclude that the situational awareness, far away from an
potential conflict, is more valuable for preventing potential conflicts in

the
first place than the actual warning facility.=20

Countless times that Flarm has identified and displayed glider within a
km
of me that I had not seen and might never have seen.

I have used only the 'butterfly' display. To be clear, of course I am
seeing target alerts all the time. That is not a problem, and even
occasionally interesting (such as when someone starts following).
The problem is with false collision warnings. Many pilots appear to (and
some of my pupils certainly do) find it almost impossible to resist turning

away from the Flarm direction of the 'threat', before they have seen the
target. That is dangerous, as I wrote in a post yesterday. And note that
the Flarm direction is often significantly different from the true
direction
(occasionally diametrically opposite), as it is track-based, not heading-
based.

I can see that my experience of Flarm in a very busy environment (the
French Alps) will be very different from that of those flying largely in
isolation (such as flatlands, particularly with what I would regard as high

cloudbases (I'm a Brit!))
J.

James, if you are plagued by false alarms coming even from the wrong heading, I am all the more curious. I have not had any false alarms, perhaps some false negatives (probably should had been an alarm). Never from the wrong direction. Do you have the IGC files from a flight in which you remember that happening? It would be interesting to put it into SeeYou or other software (or even look at it in a text editor) to see what the accuracy of fix was. I have noticed that the Flarm GPS is typically reporting a larger error, and in some cases quite large. I'm not sure what the algorithms do with the precision of fix, but it seems like that is the most likely source of the errors you describe. For example the Flarm IGC file from my glider will show a typical precision of fix of around 3 - 4 meters, but sometimes it will go up to 30-40 for unknown reasons. The Air Avionics gps will show a precision of 1 - 2 meters on the same flight and might also go up in the same areas but not as much. Ridge flying in the Alps you might have the antenna shaded on one or more sides, which will increase the HDOP. The precision is the normally the last three digits of the B record in the IGC file. All of my flying is high altitude and with a clear view of the sky.

What James may be referring to is the fact that Flarm indications are in
relation to your ground track not heading. The extreme example is if
flying in very strong winds, say in wave, and actually going backwards.
Another glider coming from your 6 o'clock will actually show as head on.
This effect is still there in any cross wind.
This is a fundamental flaw in Flarm, which surely could be much improved by
building in a wind algorithm to correct the indication nearer to heading.
All navigation programs have them.
Dave




At 03:22 27 November 2015, jfitch wrote:
On Thursday, November 26, 2015 at 2:45:07 PM UTC-8, James Metcalfe wrote:
At 21:29 25 November 2015, jfitch wrote:
I am curious about your experience with the interface. Did you just
have
the BF display, or was the Flarm also displaying targets on a
moving=20
map?

I have not had any Flarm warnings that would have saved a midair (3=20
years
with it now). But I have always had Flarm targets displayed on the
glide
computer moving map, and so nearly always see them long before they=20
could be
considered a threat. Two times in those three years I have gotten an
unexpected warning, though not close enough to require action to
avoid=
=20
collision.
I use those events as a learning experience to see how I need to
change=
=20
my
scans and operations, so that they do not happen again.

From this I conclude that the situational awareness, far away from an
potential conflict, is more valuable for preventing potential
conflicts
=
in
=20
the
first place than the actual warning facility.=3D20

Countless times that Flarm has identified and displayed glider within
a=
=20
km
of me that I had not seen and might never have seen.
=20
I have used only the 'butterfly' display. To be clear, of course I
am=20
seeing target alerts all the time. That is not a problem, and even=20
occasionally interesting (such as when someone starts following).
The problem is with false collision warnings. Many pilots appear to
(and=
=20
some of my pupils certainly do) find it almost impossible to resist
turni=
ng
=20
away from the Flarm direction of the 'threat', before they have seen
the=
=20
target. That is dangerous, as I wrote in a post yesterday. And note
that=
=20
the Flarm direction is often significantly different from the true
direction=20
(occasionally diametrically opposite), as it is track-based, not
heading-
based.
=20
I can see that my experience of Flarm in a very busy environment
(the=20
French Alps) will be very different from that of those flying largely
in=
=20
isolation (such as flatlands, particularly with what I would regard as
hi=
gh
=20
cloudbases (I'm a Brit!))
J.

James, if you are plagued by false alarms coming even from the wrong
headin=
g, I am all the more curious. I have not had any false alarms, perhaps
some=
false negatives (probably should had been an alarm). Never from the
wrong
=
direction. Do you have the IGC files from a flight in which you remember
th=
at happening? It would be interesting to put it into SeeYou or other
softw=
are (or even look at it in a text editor) to see what the accuracy of fix
w=
as. I have noticed that the Flarm GPS is typically reporting a larger
error=
, and in some cases quite large. I'm not sure what the algorithms do with
t=
he precision of fix, but it seems like that is the most likely source of
th=
e errors you describe. For example the Flarm IGC file from my glider will
s=
how a typical precision of fix of around 3 - 4 meters, but sometimes it
wil=
l go up to 30-40 for unknown reasons. The Air Avionics gps will show a
prec=
ision of 1 - 2 meters on the same flight and might also go up in the same
a=
reas but not as much. Ridge flying in the Alps you might have the antenna
s=
haded on one or more sides, which will increase the HDOP. The precision
is
=
the normally the last three digits of the B record in the IGC file. All
of
=
my flying is high altitude and with a clear view of the sky.

"This is a fundamental flaw in Flarm, which surely could be much improved by
building in a wind algorithm to correct the indication nearer to heading.
All navigation programs have them."

As another poster mentioned, you really need a heading input to achieve this. Whilst PNA's use drift while circling amongst other methods to determine the wind, they require frequent & sustained 'circles' to achieve this - not so good for wave & ridge. LX quote 3 circles from memory and all the operating notes warn of the associated unreliability. An attempt to use an algorithm to achieve this in Flarm would result in large variations in accuracy. Sometimes the relative bearings provided would be correct and sometimes, they wouldn't. Though currently an imperfect system, at least it's consistent.

CJ

James mentioned false alarms while diametrically opposed in thermals. That is highly unlikely to be due to wind drift.

What James may be referring to is the fact that Flarm indications are in
relation to your ground track not heading. The extreme example is if
flying in very strong winds, say in wave, and actually going backwards.
Another glider coming from your 6 o'clock will actually show as head on.
This effect is still there in any cross wind.
This is a fundamental flaw in Flarm, which surely could be much improved by
building in a wind algorithm to correct the indication nearer to heading.
All navigation programs have them.
Dave




At 03:22 27 November 2015, jfitch wrote:
On Thursday, November 26, 2015 at 2:45:07 PM UTC-8, James Metcalfe wrote:
At 21:29 25 November 2015, jfitch wrote:
I am curious about your experience with the interface. Did you just
have
the BF display, or was the Flarm also displaying targets on a
moving=20
map?

I have not had any Flarm warnings that would have saved a midair (3=20
years
with it now). But I have always had Flarm targets displayed on the
glide
computer moving map, and so nearly always see them long before they=20
could be
considered a threat. Two times in those three years I have gotten an
unexpected warning, though not close enough to require action to
avoid=
=20
collision.
I use those events as a learning experience to see how I need to
change=
=20
my
scans and operations, so that they do not happen again.

From this I conclude that the situational awareness, far away from an
potential conflict, is more valuable for preventing potential
conflicts
=
in
=20
the
first place than the actual warning facility.=3D20

Countless times that Flarm has identified and displayed glider within
a=
=20
km
of me that I had not seen and might never have seen.
=20
I have used only the 'butterfly' display. To be clear, of course I
am=20
seeing target alerts all the time. That is not a problem, and even=20
occasionally interesting (such as when someone starts following).
The problem is with false collision warnings. Many pilots appear to
(and=
=20
some of my pupils certainly do) find it almost impossible to resist
turni=
ng
=20
away from the Flarm direction of the 'threat', before they have seen
the=
=20
target. That is dangerous, as I wrote in a post yesterday. And note
that=
=20
the Flarm direction is often significantly different from the true
direction=20
(occasionally diametrically opposite), as it is track-based, not
heading-
based.
=20
I can see that my experience of Flarm in a very busy environment
(the=20
French Alps) will be very different from that of those flying largely
in=
=20
isolation (such as flatlands, particularly with what I would regard as
hi=
gh
=20
cloudbases (I'm a Brit!))
J.

James, if you are plagued by false alarms coming even from the wrong
headin=
g, I am all the more curious. I have not had any false alarms, perhaps
some=
false negatives (probably should had been an alarm). Never from the
wrong
=
direction. Do you have the IGC files from a flight in which you remember
th=
at happening? It would be interesting to put it into SeeYou or other
softw=
are (or even look at it in a text editor) to see what the accuracy of fix
w=
as. I have noticed that the Flarm GPS is typically reporting a larger
error=
, and in some cases quite large. I'm not sure what the algorithms do with
t=
he precision of fix, but it seems like that is the most likely source of
th=
e errors you describe. For example the Flarm IGC file from my glider will
s=
how a typical precision of fix of around 3 - 4 meters, but sometimes it
wil=
l go up to 30-40 for unknown reasons. The Air Avionics gps will show a
prec=
ision of 1 - 2 meters on the same flight and might also go up in the same
a=
reas but not as much. Ridge flying in the Alps you might have the antenna
s=
haded on one or more sides, which will increase the HDOP. The precision
is
=
the normally the last three digits of the B record in the IGC file. All
of
=
my flying is high altitude and with a clear view of the sky.

What James may be referring to is the fact that Flarm indications are in
relation to your ground track not heading. The extreme example is if
flying in very strong winds, say in wave, and actually going backwards.
Another glider coming from your 6 o'clock will actually show as head on.
This effect is still there in any cross wind.
This is a fundamental flaw in Flarm, which surely could be much improved by
building in a wind algorithm to correct the indication nearer to heading.
All navigation programs have them.
Dave




At 03:22 27 November 2015, jfitch wrote:
On Thursday, November 26, 2015 at 2:45:07 PM UTC-8, James Metcalfe wrote:
At 21:29 25 November 2015, jfitch wrote:
I am curious about your experience with the interface. Did you just
have
the BF display, or was the Flarm also displaying targets on a
moving=20
map?

I have not had any Flarm warnings that would have saved a midair (3=20
years
with it now). But I have always had Flarm targets displayed on the
glide
computer moving map, and so nearly always see them long before they=20
could be
considered a threat. Two times in those three years I have gotten an
unexpected warning, though not close enough to require action to
avoid=
=20
collision.
I use those events as a learning experience to see how I need to
change=
=20
my
scans and operations, so that they do not happen again.

From this I conclude that the situational awareness, far away from an
potential conflict, is more valuable for preventing potential
conflicts
=
in
=20
the
first place than the actual warning facility.=3D20

Countless times that Flarm has identified and displayed glider within
a=
=20
km
of me that I had not seen and might never have seen.
=20
I have used only the 'butterfly' display. To be clear, of course I
am=20
seeing target alerts all the time. That is not a problem, and even=20
occasionally interesting (such as when someone starts following).
The problem is with false collision warnings. Many pilots appear to
(and=
=20
some of my pupils certainly do) find it almost impossible to resist
turni=
ng
=20
away from the Flarm direction of the 'threat', before they have seen
the=
=20
target. That is dangerous, as I wrote in a post yesterday. And note
that=
=20
the Flarm direction is often significantly different from the true
direction=20
(occasionally diametrically opposite), as it is track-based, not
heading-
based.
=20
I can see that my experience of Flarm in a very busy environment
(the=20
French Alps) will be very different from that of those flying largely
in=
=20
isolation (such as flatlands, particularly with what I would regard as
hi=
gh
=20
cloudbases (I'm a Brit!))
J.

James, if you are plagued by false alarms coming even from the wrong
headin=
g, I am all the more curious. I have not had any false alarms, perhaps
some=
false negatives (probably should had been an alarm). Never from the
wrong
=
direction. Do you have the IGC files from a flight in which you remember
th=
at happening? It would be interesting to put it into SeeYou or other
softw=
are (or even look at it in a text editor) to see what the accuracy of fix
w=
as. I have noticed that the Flarm GPS is typically reporting a larger
error=
, and in some cases quite large. I'm not sure what the algorithms do with
t=
he precision of fix, but it seems like that is the most likely source of
th=
e errors you describe. For example the Flarm IGC file from my glider will
s=
how a typical precision of fix of around 3 - 4 meters, but sometimes it
wil=
l go up to 30-40 for unknown reasons. The Air Avionics gps will show a
prec=
ision of 1 - 2 meters on the same flight and might also go up in the same
a=
reas but not as much. Ridge flying in the Alps you might have the antenna
s=
haded on one or more sides, which will increase the HDOP. The precision
is
=
the normally the last three digits of the B record in the IGC file. All
of
=
my flying is high altitude and with a clear view of the sky.

At 03:22 27 November 2015, jfitch wrote:
James, if you are plagued by false alarms coming even from
the wrong
heading, I am all the more curious. I have not had any false
alarms, perhaps
some false negatives (probably should had been an alarm).
Never from the wrong
direction. Do you have the IGC files from a flight in which you
remember
that happening? It would be interesting to put it into SeeYou or
other
software (or even look at it in a text editor) to see what the
accuracy of fix
was. I have noticed that the Flarm GPS is typically reporting a
larger
error, and in some cases quite large. I'm not sure what the
algorithms do with
the precision of fix, but it seems like that is the most likely
source of
the errors you describe. For example the Flarm IGC file from
my glider will
show a typical precision of fix of around 3 - 4 meters, but
sometimes it
will go up to 30-40 for unknown reasons. The Air Avionics gps
will show a
precision of 1 - 2 meters on the same flight and might also go
up in the same
areas but not as much. Ridge flying in the Alps you might have
the antenna
shaded on one or more sides, which will increase the HDOP.
The precision is
the normally the last three digits of the B record in the IGC
file. All of
my flying is high altitude and with a clear view of the sky.

Others have now posted in more detail on the track vs. heading
errors of Flarm. These are inevitable (until wind information is
available to Flarm), and not (I’m confident) a problem with any
of the 3 installations which I have used. I’m afraid I have not
kept a log of the various incidents to which I have referred, nor
do I have the IGC files.

It seems to me that you yourself have provided the explanation
of the differences in our experiences of Flarm:
- You fly largely alone, in wide open spaces, but occasionally
meeting other gliders on the same cloud street.
- I fly mainly in a busy Alpine setting, constantly close to (and
co-operating with) other gliders on ridges and in thermals. (If I
find myself alone I am reassured that it is not just me who is
finding the conditions difficult to soar in!)
J.