Is FLARM helpful?

With all due respect, it should go without saying that if you are going to quote someone, do not later paraphrase with a completely new meaning!!!! What I said is "shouldn't preserving life be our highest goal". I did not say nor did I mean what you later paraphrased as "We should not avoid risk as our highest goal". Those are your words intentional miscontrueing plain simple English that I clearly communicated to anyone with a fourth grade education! Thank you very much.

On Friday, November 27, 2015 at 9:45:06 AM UTC-8, Jim White wrote:
At 06:34 27 November 2015, Jonathan St. Cloud wrote:

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

..Jim White wrote:

...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....


Jim

Once again I'll say - That is not the way it works. The 2 km does not apply to an aircraft determined to be a threat. In the case stated above the alarm and display would go off at x secs regardless of the distance. I am not sure what the number of seconds is but it is based on a safe reaction time. The warning would be limited by the reception range of the FLARM set up and any limitations the pilot has set in $PFLAU portion of the configuration file. This would be true stealth or not. The specifics of how the threat is painted and the audio warning is left to manufacturer of the display device.

Proximate aircraft which are not a threat are only displayed if they are within 2 km and +/- 300 m, etc.

XC

On Fri, 27 Nov 2015 12:49:50 -0800, ucanemailmoi 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.

I think its a bit longer than that.

A closing speed of 496 kph is 138 m/s, so it will take 14.5 seconds
between first warning at 2km separation to the collision if nobody takes
avoiding action.


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

On Fri, 27 Nov 2015 11:27:06 -0800, jfitch wrote:

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.

Yes - agreed. I wasn't criticising FLARM at all for this. IMO the reality
of thermal gaggles is that everybody *must* maintain situational
awareness in a multiply occupied thermal. Thinking about it a bit
further, if everybody at more or less the same height in a thermal flies
sensibly, the time to go from safe to collision takes enough time to make
avoidance fairly easy. It would take at least one pilot to be grossly out
of position to make a collision imminent (think leaving by blasting
across the centre or getting too close behind or below another glider).
FLARM will spot a dangerous joining manoeuvre but whether the warning
would do you any good may depend on where the other glider(s) in the
thermal are, i.e. do you have an escape route that doesn't endanger
anybody else.


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

From a previous post:

"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."

Uh- I don't think so. 2 m in .25 sec = 8 km/sec = 480 km/min = 28,800 km/hr = 17,856 mph = orbital velocity.

Obviously not a script writer for "The Martian."

"Interstellar," maybe.

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

Yet peculiarly in the pilots poll, twice as many pilots said non-stealth Flarm enhanced enjoyment of a contest, as wanted it mandatory. In nationals 30% wanted mandatory stealth, in regionals 20%. Yet 40% said keeping track of the other gliders through non-stealth flarm enhanced their enjoyment of the contest. Looking at all of the responses to those three questions one can only conclude that a significant number of pilots do not want to enjoy contests. Maybe that's why participation is declining?

Oops!

Make the first line read "2 KM in .25 sec"

On Friday, November 27, 2015 at 2:07:01 PM UTC-8, XC wrote:
Once again I'll say - That is not the way it works. The 2 km does not apply to an aircraft determined to be a threat. In the case stated above the alarm and display would go off at x secs regardless of the distance. I am not sure what the number of seconds is but it is based on a safe reaction time. The warning would be limited by the reception range of the FLARM set up and any limitations the pilot has set in $PFLAU portion of the configuration file. This would be true stealth or not. The specifics of how the threat is painted and the audio warning is left to manufacturer of the display device.

Proximate aircraft which are not a threat are only displayed if they are within 2 km and +/- 300 m, etc.

XC

I don't think that's the issue people are raising. The only way you get a warning from Flarm is if the glider is on an intersecting track within a fairly narrow "uncertainty cone". It is only valid over any distance for gliders that don't maneuver. As we all know that is rarely the case - glider maneuver all the time.

The issue is that a glider that hooks a turnpoint or leaves a thermal or otherwise changes course can go from being invisible to a threat at a distance that is roughly 10-15 seconds away from impact.

The RC is aware of this shortcoming and is engaging with the IGC and Flarm to ensure that course changes cannot generate surprise threats without proper IDs (remember, a radio call to a known Contest ID to coordinate evasive action is the best practice in head-to-head scenarios). It is particularly an issue for high-altitude, high speed street flying that is common in the US west and other places where converging speeds can top 350 MPH. At 2km for Flarm stealth mode this is a 12 seconds of warning. Most pilots who fly under these conditions use longer range situational awareness to avoid conflicts rather than having to react with very little time to: 1) identify and orient the threat, 2) determine the best course of action, 3) raise the other glider on the radio by Contest Number - or worse, Flarm ID (who memorizes theirs?), 4) coordinate an evasive maneuver that isn't "you zig, I zag". Ask the guys that fly the convergence and strong streets out west all the time. Less than a minute to do all that concerns them - deeply. I asked them and got their feedback.

Also, I don't think if you ask the guys in the middle of the scoresheet they'd be super wild about deliberately creating more landouts (and everything that goes with that in terms of hassle and the odd insurance claim) out of some sense that missing a thermal on a random glide that someone who flew 1/16 of a mile to the east stumbled into for a save somehow is more valid. Mostly we devalue contests with landouts because we think landouts are an indicator of less valid conditions. In fact we polled people and they said what they think.

But that's another discussion about philosophy. :-)

9B

On Friday, November 27, 2015 at 2:12:24 PM UTC-8, Martin Gregorie wrote:
On Fri, 27 Nov 2015 12:49:50 -0800, ucanemailmoi 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.

I think its a bit longer than that.

A closing speed of 496 kph is 138 m/s, so it will take 14.5 seconds
between first warning at 2km separation to the collision if nobody takes
avoiding action.


LOL. I think he meant 1/4 minute. At 110 kts at 17,500 and 40 deg F it's closer to 1/6 of a minute.

9B

The case that folks are making regarding high converging speeds are in clouds streets, wave and ridge lift. Theses are predictable situations that are easily handled by the FLARM algorithm. In the worse case scenario, 10-15 seconds is plenty of time to alter course to avoid a mid-air

The argument that a radio call to a known ID is the best course of action is false. The best way to avoid a mid-air is to turn to avoid the danger using predetermined right-of-way rules, not to establish radio communication and coordinate a plan.

Lastly, good glider pilots don't stumble into saves. They know where the lift is likely to be. They manage risk to get there with altitude to use it and have a back up plan. Some people are good at this and others are not as good. The score sheet should reflect this fact. The rules should ensure the integrity of the sport and keep it the adventure it was always supposed to be - not water it down. You'd attract a lot more people to the sport by having soaring heroes like we used to have rather than trying to placate everyone's desire to make it home for dinner.

XC


I don't think that's the issue people are raising. The only way you get a warning from Flarm is if the glider is on an intersecting track within a fairly narrow "uncertainty cone". It is only valid over any distance for gliders that don't maneuver. As we all know that is rarely the case - glider maneuver all the time.

The issue is that a glider that hooks a turnpoint or leaves a thermal or otherwise changes course can go from being invisible to a threat at a distance that is roughly 10-15 seconds away from impact.

The RC is aware of this shortcoming and is engaging with the IGC and Flarm to ensure that course changes cannot generate surprise threats without proper IDs (remember, a radio call to a known Contest ID to coordinate evasive action is the best practice in head-to-head scenarios). It is particularly an issue for high-altitude, high speed street flying that is common in the US west and other places where converging speeds can top 350 MPH. At 2km for Flarm stealth mode this is a 12 seconds of warning. Most pilots who fly under these conditions use longer range situational awareness to avoid conflicts rather than having to react with very little time to: 1) identify and orient the threat, 2) determine the best course of action, 3) raise the other glider on the radio by Contest Number - or worse, Flarm ID (who memorizes theirs?), 4) coordinate an evasive maneuver that isn't "you zig, I zag".. Ask the guys that fly the convergence and strong streets out west all the time. Less than a minute to do all that concerns them - deeply. I asked them and got their feedback.

Also, I don't think if you ask the guys in the middle of the scoresheet they'd be super wild about deliberately creating more landouts (and everything that goes with that in terms of hassle and the odd insurance claim) out of some sense that missing a thermal on a random glide that someone who flew 1/16 of a mile to the east stumbled into for a save somehow is more valid.. Mostly we devalue contests with landouts because we think landouts are an indicator of less valid conditions. In fact we polled people and they said what they think.

But that's another discussion about philosophy. :-)

9B