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Is FLARM helpful?



 
 
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  #91  
Old November 28th 15, 10:19 PM posted to rec.aviation.soaring
Andy Blackburn[_3_]
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Posts: 608
Default Is FLARM helpful?

On Saturday, November 28, 2015 at 11:15:23 AM UTC-8, wrote:

The initial thought I had at Uvalde is the he probably had his head down adjusting the scale on his PDA as he went into (out of) the turn. This is just speculation but it truly was what we were thinking on that day.


We'll never know what Chris was doing and I'm loathe to get too much deeper into a painful memory in this discussion. I did talk to the other pilot, who's a friend, at great length - it's in the Soaring article on Flarm from 2014. Suffice it to say at least one person was looking and scanning pretty hard. It's a very challenging visual problem for humans - we weren't bred to pick these kinds of thing up.


Andy, you're really overselling this. I never said I was in favor of more land outs, just that pilots should not be able to artificially increase their achieved speeds by routinely using other people's thermals which are conveniently labeled with climb rates.


I've always just been looking for the scenario that is being solved for. Either there will be more landouts from missed saves or there's not much benefit being generated. If I accept your point but assume zero incremental landouts, just that one course line might have a superior climb in it and some other line might not. First, that's one scoop skill, one scoop local knowledge and one scoop dumb luck). I wager for the non-random part it benefits different pilots on different days by a minute or two - or 8-14 points on the days when it works. So you're up 8 one day, no benefit three other days and down 14 another day for minus 6 points net at the end of a week. It's so far down in the noise of random events at a contest that the signal to noise ratio isn't even measurable. Add to that the fact that pilots who systematically take other people's thermals rather than their own generate about 10-15% slower climbs on average (actual data from suspected leech-heavy contests). At the end of the contest you end up with people who try to use Flarm to follow being down several hundred points for having been a sucker - not counting any other shortcomings they may have.

I'm fine with deleting climb rates, I find them useless anyway, they are snapshots with no total energy - I normally pick up the pullup (+10 its or so), followed by a lot of randomness.


Everyone should count out loud 10 seconds as a worse case scenario and see if it enough time to avoid a glider or a formation of gliders while looking outside your glider. I think it is. If folks want to go back in forth between outside and your cockpit display and analyze things then they are going to get caught looking in the wrong place.


Should be fine. Hope it'll be fine - until you see the other guy in quartering trail behind the alarm target or realize the target glider turned right just as you turned left. It's hard to pick that up on the display (do you look out the canopy or down at the display to sort that out?) at one update per second so you need a couple of updates to see where he went - or you try to pick him up by looking in that direction, but your odds of seeing him in time are about 50/50 - from FAA and NTSB experimental studies.

The suggestion is to have some range so you avoid collision courses all together rather than waiting for them to happen.

Yes these are small probabilities of horrific events - but that was the whole point of Flarm in the first place. Part of the reason why stealth mode "works just fine" is that flying without Flarm works just fine even if you don't look out the window - almost all the time.

I'll surely fly in a stealth mandated contest if there is no reasonable alternative, but I've been finding the less restricted OLC/XC events pretty enjoyable too and it will certainly affect my choice of mix. That's just me. The poll would indicate more pilots are not fond of stealth than are fond of stealth.9q1

9B
  #92  
Old November 28th 15, 10:59 PM posted to rec.aviation.soaring
Andy Blackburn[_3_]
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Posts: 608
Default Is FLARM helpful?

On Saturday, November 28, 2015 at 1:19:12 PM UTC-8, Andy Blackburn wrote:

One other perspective. I really hate getting collision alarms - particularly on course where you by definition have missed something if it happens. It generates a near-panic emotional response because you are potentially seconds from being hit. A little tunnel vision sets in as you look down to the display to try to make out the direction and relative altitude of the target and then swing your gaze to pick them up - and figure out what to do. I have on occasion picked up the wrong (farther away) glider in the same general direction - that leads to a very nasty surprise.

Flarm is architected as a multi-layer defense against collisions. The collision alarm is the last line of defense and the broader target tracking is the more important preventative layer - much the way ATC vectoring of traffic is the more important part of keeping airliners apart and TCAS is the last line of defense.

I find degrading the first line of defense and relying only on the last line of defense to not only be somewhat additionally risky because you are counting on everyone to do the right thing in a few seconds under stress, but it is also more anxiety producing to rely almost entirely on an alarm of an impending collision, rather than staying out of each other's way - even if it works out perfectly every time an alarm happens. I don't think very many people would be comfortable getting on airliners if they sent all the air traffic controllers home and relied just on TCAS - even if it worked perfectly every single time.

I know - I've totally lost my sense of excitement and adventure.

9B
  #93  
Old November 29th 15, 12:23 AM posted to rec.aviation.soaring
jfitch
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Posts: 1,134
Default Is FLARM helpful?

On Saturday, November 28, 2015 at 6:51:46 AM UTC-8, John Godfrey (QT) wrote:


WRT thermals, one prior poster observed that Winpilot is excellent for displaying gliders in a thermal. The idea of someone in a thermal not looking out the window 100% of the time is troubling to me. There have been at least two instances I am personally aware of where FLARM equipped gliders have collided in a thermal.

QT


WRT to tac display in thermals, I am more concerned about the gliders I cannot see, than the ones I can. The latter have already been accounted for. The former will not be seen even if I put 200% of my attention outside the cockpit. These are the ones behind or below in the circle. A poor tactical display may require too much attention to process, leading to a loss of overall situational awareness. A good one requires a 1 second glance to process everything.
  #94  
Old November 29th 15, 12:37 AM posted to rec.aviation.soaring
jfitch
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Posts: 1,134
Default Is FLARM helpful?

On Saturday, November 28, 2015 at 1:35:36 AM UTC-8, wrote:
1/4 minute is ample time - that is about when Flarm issues its first acoustic collision alert. I have participated in several head on collision scenarios during a Flarm trial. Even waiting until the third level of Flarm alarm before reacting all that is required is a gentle change of direction a few degrees. The key thing is that Flarm has alerted you to visually acquire the potential threat that you might not otherwise have done.

BTW my strong belief is the the first response to a Flarm acoustic alert should be to look along track, to see a possible head on threat, before looking at the visual display. Head on threats are the most high energy.

There is far too much concentration on Flarm visual displays (eyes down) instead of the acoustic alert (eyes outside).


1/4 minute may be ample in controlled tests between two gliders. It may not be in the real world.

Imagine three gliders at 200 kph slightly separated vertically, horizontally, and longitudenally running a street, meeting 3 gliders similarly displaced on an opposite heading. This is not all that uncommon over the Whites in the west. You have 12 seconds to visually ID the three opposing gliders, account for the two with you, decide on an evasive action and implement it, all without knowing the plans of the 5 other gliders, and making further adjustments when 2 of the other 5 didn't do what you guessed. You cannot visually ID a glider head on against clouds at 2 km, hard even at 1 in a short time. Had you seen them 5 or 10 km away, the situation will not even arise since a minor adjustment would have completely eliminated the possibility.

I have argued against considering Flarm to be that much of a safety device, given that mid air collisions are quite rare. But to have it in the cockpit and then disable it in precisely the conditions most likely to cause a mid air (most of them have been in contests) is odd logic.
  #95  
Old November 29th 15, 08:40 AM posted to rec.aviation.soaring
[email protected]
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Posts: 374
Default Is FLARM helpful?

There seems to be some misunderstanding and dysfunctional response to Flarm alarms being described here. When an alarm sounds look out and scan fully and quickly (including above) rather than looking at the display first. If you see no glider that appears to be on a collision course you are in the same position as you would be if you didn't have Flarm but were being really attentive to see and avoid PLUS the other glider that you can't see is also getting an alarm and he can probably see you if you can't see him. People seem to forget in theur response to alerts that Flarm is two way and we are also giving out alarms.

Local soaring for my club is many gliders on the same short ridge soaring back and forth at similar altitudes and we can get several Flarm alerts per hour on a busy day. Sometines it isn't possible to tell which glider you're sharing an alert with. I rarely look at the display in gaggles and local hill soaring and if ahead and all around and above seems clear and the then I just make a slight deviation and trust that I am in the view of the other glider. Often alerts go away without me knowing where it came from. In this scenario, as in busy thermals, we Flarm equipped pilots are far better off by having our See and Avoid continually stimulated.

The problem is gliders that don't have Flarn and we had a collision between two of those on our ridge a couple of years ago.
  #96  
Old November 29th 15, 08:59 AM posted to rec.aviation.soaring
Jonathan St. Cloud
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Posts: 1,463
Default Is FLARM helpful?

So let me understand what you are saying. You are flying along doing a scan as always and then when you get a Flarm alert you continue the same scan, only more quickly, that has not yielded any results because to glance at the screen for a position of the possible collision target would be dysfunctional? And oh, if you have not seen the collision target glider, don't worry he has probably seen you. Just beautiful.

On Saturday, November 28, 2015 at 11:41:01 PM UTC-8, wrote:
There seems to be some misunderstanding and dysfunctional response to Flarm alarms being described here. When an alarm sounds look out and scan fully and quickly (including above) rather than looking at the display first. If you see no glider that appears to be on a collision course you are in the same position as you would be if you didn't have Flarm but were being really attentive to see and avoid PLUS the other glider that you can't see is also getting an alarm and he can probably see you if you can't see him. People seem to forget in theur response to alerts that Flarm is two way and we are also giving out alarms.


The problem is gliders that don't have Flarn and we had a collision between two of those on our ridge a couple of years ago.

  #97  
Old November 29th 15, 04:33 PM posted to rec.aviation.soaring
James Metcalfe
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Posts: 50
Default Is FLARM helpful?

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.


  #98  
Old November 29th 15, 05:45 PM posted to rec.aviation.soaring
jfitch
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Posts: 1,134
Default Is FLARM helpful?

On Sunday, November 29, 2015 at 7:45:09 AM UTC-8, James Metcalfe wrote:
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.


A diametrically opposed false alarm in a thermal suggests wind in the 30 - 60 knot range. I have not seen good thermal development in those conditions, even in extremely strong western desert conditions. I have flown in gaggles of 10 - 15 gliders near the same altitude in the same thermal and have never had such a false alarm.
  #99  
Old November 29th 15, 05:49 PM posted to rec.aviation.soaring
jfitch
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Posts: 1,134
Default Is FLARM helpful?

On Saturday, November 28, 2015 at 11:41:01 PM UTC-8, wrote:
There seems to be some misunderstanding and dysfunctional response to Flarm alarms being described here. When an alarm sounds look out and scan fully and quickly (including above) rather than looking at the display first. If you see no glider that appears to be on a collision course you are in the same position as you would be if you didn't have Flarm but were being really attentive to see and avoid PLUS the other glider that you can't see is also getting an alarm and he can probably see you if you can't see him. People seem to forget in theur response to alerts that Flarm is two way and we are also giving out alarms.

Local soaring for my club is many gliders on the same short ridge soaring back and forth at similar altitudes and we can get several Flarm alerts per hour on a busy day. Sometines it isn't possible to tell which glider you're sharing an alert with. I rarely look at the display in gaggles and local hill soaring and if ahead and all around and above seems clear and the then I just make a slight deviation and trust that I am in the view of the other glider. Often alerts go away without me knowing where it came from. In this scenario, as in busy thermals, we Flarm equipped pilots are far better off by having our See and Avoid continually stimulated.

The problem is gliders that don't have Flarn and we had a collision between two of those on our ridge a couple of years ago.


Another point about tac displays and warnings vs. attention: A voice warning system eliminates any visual attention deficit, no glance it necessary. The voice warnings from the Air Avionics vario are very good. On the other hand keeping track of nearby traffic on the tactical display when they are farther away, is exactly the time you can afford the attention to it, process the information, and plan avoidance maneuvers, compared to an unexpected warning giving only a few seconds to do all of that.
  #100  
Old November 29th 15, 07:15 PM posted to rec.aviation.soaring
[email protected]
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Posts: 374
Default Is FLARM helpful?

On Sunday, November 29, 2015 at 4:45:58 PM UTC, jfitch wrote:
On Sunday, November 29, 2015 at 7:45:09 AM UTC-8, James Metcalfe wrote:
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.


A diametrically opposed false alarm in a thermal suggests wind in the 30 - 60 knot range. I have not seen good thermal development in those conditions, even in extremely strong western desert conditions. I have flown in gaggles of 10 - 15 gliders near the same altitude in the same thermal and have never had such a false alarm.


Given that Flarm is comparing predicted flight paths of the two gliders and issuing alerts based on calculations of possible conflicts up to 18 seconds ahead you would have to be certain that both gliders were flying exactly concentric circles of the same radius and speed before you could be sure that an alert from a diametrically opposed glider was a "false alarm". It would be more likely that the Flarm units were performing as designed and within their fairly large buffers 18 seconds ahead. Granted, our personal buffer zones in thermals are tighter than the those of the Flarm algorithms. As I wrote previously I have demonstrated in flight to a copilot that what he thought was a false alarm from an almost diametrically opposed glider was in fact proven to be a valid alarm about 3/4 turn later. The other glider was diametrically opposed but not flying concentrically with us.

 




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