Is FLARM helpful?

At 13:30 27 November 2015, wrote:
"This is a fundamental flaw in Flarm, which surely could be much improved
b=
y=20
building in a wind algorithm to correct the indication nearer to
heading.=
=20
All navigation programs have them."

As another poster mentioned, you really need a heading input to achieve
thi=
s. Whilst PNA's use drift while circling amongst other methods to
determin=
e the wind, they require frequent & sustained 'circles' to achieve this -
n=
ot so good for wave & ridge. LX quote 3 circles from memory and all the
op=
erating notes warn of the associated unreliability. An attempt to use an
a=
lgorithm to achieve this in Flarm would result in large variations in
accur=
acy. Sometimes the relative bearings provided would be correct and
sometim=
es, they wouldn't. Though currently an imperfect system, at least it's
con=
sistent.

CJ

I only mentioned wave to illustrate the extreme example. Some error is
always there unless you are flying straight up or down wind. It is far
from consistent, the amount depends on the wind speed and your angle to it,
two variables.
So whats wrong with flying 2/3 circles, I often circle in wave. In any case
Paolo Ventrafridda developed a method for LK8000, of flying S & L on one of
several headings for say 10 secs at a constant airspeed.
If the will is there, it can be done, and even if slightly imperfect, it
would be better than the present almost always wrong indication.
However another approach would be a way of manually putting the wind into
Flarm, using the vario/navigator readout, which I'm sure everyone flying
with Flarm, is equipped with as well.
Dave

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

On Friday, November 27, 2015 at 4:00:05 PM UTC, David Salmon wrote:
At 13:30 27 November 2015, wrote:
"This is a fundamental flaw in Flarm, which surely could be much improved
b=
y=20
building in a wind algorithm to correct the indication nearer to
heading.=
=20
All navigation programs have them."

As another poster mentioned, you really need a heading input to achieve
thi=
s. Whilst PNA's use drift while circling amongst other methods to
determin=
e the wind, they require frequent & sustained 'circles' to achieve this -
n=
ot so good for wave & ridge. LX quote 3 circles from memory and all the
op=
erating notes warn of the associated unreliability. An attempt to use an
a=
lgorithm to achieve this in Flarm would result in large variations in
accur=
acy. Sometimes the relative bearings provided would be correct and
sometim=
es, they wouldn't. Though currently an imperfect system, at least it's
con=
sistent.

CJ

I only mentioned wave to illustrate the extreme example. Some error is
always there unless you are flying straight up or down wind. It is far
from consistent, the amount depends on the wind speed and your angle to it,
two variables.
So whats wrong with flying 2/3 circles, I often circle in wave. In any case
Paolo Ventrafridda developed a method for LK8000, of flying S & L on one of
several headings for say 10 secs at a constant airspeed.
If the will is there, it can be done, and even if slightly imperfect, it
would be better than the present almost always wrong indication.
However another approach would be a way of manually putting the wind into
Flarm, using the vario/navigator readout, which I'm sure everyone flying
with Flarm, is equipped with as well.
Dave

My colleague corresponded with Flarm during our Scottish trial in 2007 about the possibility of correcting the track/heading difference by wind estimates from circling and they said they would look it it but never introduced it. One of the obvious issues is that the modes of flight during which this difference is most obvious (ridge and wave) are less likely to entail a lot of circling. Also in mountain ridge flying we are more likely to experience varying local winds.

I think that trying to do this would introduce too many uncertainties and different calculations between gliders.

Even without Flarm a pilot who can't figure out his track versus heading when ridge flying would be looking out the window in the wrong place for conflicting gliders.

John Galloway

At 06:34 27 November 2015, Jonathan St. Cloud wrote:
I thought there were two posts worth repeating below and hope everyone
take=
s an honest look. Steve's post was poignant. I did hear the contest
committ=
ee will require Flarm in stealth mode at contests, if you have one.

Shouldn't preserving life be our highest goal, even more important than
win=
ning a contest or being annoyed by the theoretical possibility of someone
l=
eaching for a few thermals? =20

This has been done over a thousand times. If you want a super safe
competition don't leave the ground.

Competition in gliders is inherently dangerous. But, Flarm or not, it is
not probable that you will have a fatal accident. Competition pilots weigh
up risk all the time and understand that by taking part they are taking a
risk.

The risk is small and made smaller by the use of Flarm. We should not avoid
risk as our highest goal. We should aim to collectively enjoy the sport
with an appropriate level of risk - mitigated by Flarm.

I believe Flarm should be mandated in competition and also believe it
should be used in stealth mode to allow handling and soaring skill to be
more relevant than radar reading and tactical flying.

Jim

On Friday, November 27, 2015 at 12:32:47 PM UTC-5, wrote:
On Friday, November 27, 2015 at 4:00:05 PM UTC, David Salmon wrote:
At 13:30 27 November 2015, wrote:
"This is a fundamental flaw in Flarm, which surely could be much improved
b=
y=20
building in a wind algorithm to correct the indication nearer to
heading.=
=20
All navigation programs have them."

As another poster mentioned, you really need a heading input to achieve
thi=
s. Whilst PNA's use drift while circling amongst other methods to
determin=
e the wind, they require frequent & sustained 'circles' to achieve this -
n=
ot so good for wave & ridge. LX quote 3 circles from memory and all the
op=
erating notes warn of the associated unreliability. An attempt to use an
a=
lgorithm to achieve this in Flarm would result in large variations in
accur=
acy. Sometimes the relative bearings provided would be correct and
sometim=
es, they wouldn't. Though currently an imperfect system, at least it's
con=
sistent.

CJ

I only mentioned wave to illustrate the extreme example. Some error is
always there unless you are flying straight up or down wind. It is far
from consistent, the amount depends on the wind speed and your angle to it,
two variables.
So whats wrong with flying 2/3 circles, I often circle in wave. In any case
Paolo Ventrafridda developed a method for LK8000, of flying S & L on one of
several headings for say 10 secs at a constant airspeed.
If the will is there, it can be done, and even if slightly imperfect, it
would be better than the present almost always wrong indication.
However another approach would be a way of manually putting the wind into
Flarm, using the vario/navigator readout, which I'm sure everyone flying
with Flarm, is equipped with as well.
Dave

My colleague corresponded with Flarm during our Scottish trial in 2007 about the possibility of correcting the track/heading difference by wind estimates from circling and they said they would look it it but never introduced it. One of the obvious issues is that the modes of flight during which this difference is most obvious (ridge and wave) are less likely to entail a lot of circling. Also in mountain ridge flying we are more likely to experience varying local winds.

I think that trying to do this would introduce too many uncertainties and different calculations between gliders.

Even without Flarm a pilot who can't figure out his track versus heading when ridge flying would be looking out the window in the wrong place for conflicting gliders.

John Galloway

From the flarm.com press release of 2015-01-28, in part: "...It includes safety features that increase the effectiveness and robustness of collision warnings, further decreasing nuisance alarms, for example by taking into account wind."

It also talks about the FLARM TrackingServer release "...in spring 2015...", which as far as I can tell, didn't happen.

It would be helpful if someone from FLARM could comment on how the wind is taken into account, and the status of the TrackingServer. I note it would be convenient if they had a forum/bulletin board where customers of their expensive and complex products could interact with them and each other.

On Fri, 27 Nov 2015 09:31:17 -0800, jfitch wrote:

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

.... which is something I've never experienced, but maybe I've never
shared a thermal with an idiot since I've had FLARM fitted. That said, at
my club there was one collision in a thermal between two FLARM-equipped
gliders. AFAICT from talking to the pilots, one of them was far from
being on the diametrically opposite side of the thermal and then misread
the intentions of the other pilot. Under these conditions FLARM won't
help because the time between its warning being triggered and the
collision is likely to be too short for either pilot to do anything about
it.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On Friday, November 27, 2015 at 11:15:40 AM UTC-8, Martin Gregorie wrote:
On Fri, 27 Nov 2015 09:31:17 -0800, jfitch wrote:

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

... which is something I've never experienced, but maybe I've never
shared a thermal with an idiot since I've had FLARM fitted. That said, at
my club there was one collision in a thermal between two FLARM-equipped
gliders. AFAICT from talking to the pilots, one of them was far from
being on the diametrically opposite side of the thermal and then misread
the intentions of the other pilot. Under these conditions FLARM won't
help because the time between its warning being triggered and the
collision is likely to be too short for either pilot to do anything about
it.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

The short warning you get in thermals is a limitation of Flarm. Mitigated by a very good tactical screen of which there are unfortunately few examples.. One of the compromises that appear to have been made to eliminate false alarms in thermals is a very short warning distance. I have flown close to other gliders in thermals (yes they were aware) to see just when the alarms occur. I'm not criticizing Flarm for this, something I think they had to do.. Too many extraneous alarms is as bad as no alarms at all.

On a good tactical screen (the original Winpilot remains the very best by a wide margin) gives you a 3D map of all the gliders in the thermal near your altitude. Very easy at a glance to see where everyone is. I do not know of another display with this capability but I found it very informative. Unfortunately the original Winpilot doesn't work with modern equipment anymore, so the facility has been lost.

I am still seeing a lot of misinformation out there. I have two points to make supporting the use FLARM stealth mode in contests.

1) Stealth mode still allows the display and audio warning for threat aircraft no matter what the range.

and

2) FLARM used without stealth mode leads to an invalid score sheet. This is more true in eastern U.S. or European contests with lower working bands and more potential landouts.


First, I'd like folks to understand that FLARM sends two different messages to the display devices.

The $PFLAU sentence has priority and contains info about intruder alerts and obstacles. The contest ID is removed in stealth mode. Alerts are unaffected no matter the range. It really works quite well with the algorithm the FLARM people have developed.

The $PFLAA sentence is info about proximate aircraft displayed on your device. In stealth mode this info limited to aircraft within 2 km and +/- 300 meters vertically. Stealth or competition mode also removes ID, climb rate, track and speed from the display output for these proximate aircraft. It continues to use these variables to calculate the collision avoidance algorithm in $PFLAU.

Folks should read FLARM release notes for FLARM 6.02 Firmware, FLARM data port specification TFD-12 and FTD-14 FLARM Configuration Specification for full understanding. Anyway, we found in Elmira last year it worked quite well and the contest was definitely still fun for all.

High Western conditions versus lower Eastern (US) conditions: Without the use of stealth mode, in a contest with a lower working band, a pilot relying on FLARM technology can drive harder without fearing a landout, knowing there are gliders ahead to mark thermals. This does work in the east where thermals are closer together and you may be one thermal away from a landout. Even a mediocre pilot who might not even be able to get around the course by him/herself that day can use FLARM to pick the best thermals, found by others, and do fairly well on the score sheet. I agree in most cases this will not get a pilot the win. I do believe FLARM without stealth mode jumbles the middle of the score sheet and leads to an invalid result.

So, do what you want when flying cross countries at home. However, I go to contests to see how I am stacking up against some great pilots. Stealth mode (soon to have more appropriate name) is the way to go here. It retains all the safety features it was designed to deliver, keeps your eyes outside of the cockpit where they should be and at the end of the contest period the score sheet shows which pilots have the best soaring skills.

XC

"The $PFLAA sentence is info about proximate aircraft displayed on your device. In stealth mode this info limited to aircraft within 2 km and +/- 300 meters vertically. Stealth or competition mode also removes ID, climb rate, track and speed from the display output for these proximate aircraft. It continues to use these variables to calculate the collision avoidance algorithm in $PFLAU. "

Imagine two gliders flying in Utah at the nationals at 17,000 feet 100 knots indicated under cloud street on opposite courses. Say the 100 knots indicated is 134 knots true. Closure rate 268 knots or 496 kph, covering 2Km is about 1/4 a second warning. Just saying.



On Friday, November 27, 2015 at 11:57:18 AM UTC-8, XC wrote:
I am still seeing a lot of misinformation out there. I have two points to make supporting the use FLARM stealth mode in contests.

1) Stealth mode still allows the display and audio warning for threat aircraft no matter what the range.

and

2) FLARM used without stealth mode leads to an invalid score sheet. This is more true in eastern U.S. or European contests with lower working bands and more potential landouts.


First, I'd like folks to understand that FLARM sends two different messages to the display devices.

The $PFLAU sentence has priority and contains info about intruder alerts and obstacles. The contest ID is removed in stealth mode. Alerts are unaffected no matter the range. It really works quite well with the algorithm the FLARM people have developed.

The $PFLAA sentence is info about proximate aircraft displayed on your device. In stealth mode this info limited to aircraft within 2 km and +/- 300 meters vertically. Stealth or competition mode also removes ID, climb rate, track and speed from the display output for these proximate aircraft. It continues to use these variables to calculate the collision avoidance algorithm in $PFLAU.

Folks should read FLARM release notes for FLARM 6.02 Firmware, FLARM data port specification TFD-12 and FTD-14 FLARM Configuration Specification for full understanding. Anyway, we found in Elmira last year it worked quite well and the contest was definitely still fun for all.

High Western conditions versus lower Eastern (US) conditions: Without the use of stealth mode, in a contest with a lower working band, a pilot relying on FLARM technology can drive harder without fearing a landout, knowing there are gliders ahead to mark thermals. This does work in the east where thermals are closer together and you may be one thermal away from a landout.. Even a mediocre pilot who might not even be able to get around the course by him/herself that day can use FLARM to pick the best thermals, found by others, and do fairly well on the score sheet. I agree in most cases this will not get a pilot the win. I do believe FLARM without stealth mode jumbles the middle of the score sheet and leads to an invalid result.

So, do what you want when flying cross countries at home. However, I go to contests to see how I am stacking up against some great pilots. Stealth mode (soon to have more appropriate name) is the way to go here. It retains all the safety features it was designed to deliver, keeps your eyes outside of the cockpit where they should be and at the end of the contest period the score sheet shows which pilots have the best soaring skills.

XC

On Friday, November 27, 2015 at 3:49:53 PM UTC-5, wrote:

Imagine two gliders flying in Utah at the nationals at 17,000 feet 100 knots indicated under cloud street on opposite courses. Say the 100 knots indicated is 134 knots true. Closure rate 268 knots or 496 kph, covering 2Km is about 1/4 a second warning. Just saying.

What is it that you think is going to go wrong in stealth mode? My reading of flarm's docs says alerts will be delivered normally, i.e. first warning about 25 seconds before closest approach.

T8