On Friday, May 29, 2015 at 6:15:36 AM UTC-7, Mike Schumann wrote:
On Thursday, May 28, 2015 at 8:59:12 PM UTC-5, Andy Blackburn wrote:
I'll buy the beer.

Prediction, projection, position, protection. I'm not very clear on the finer points of my mother language apparently. ;-)

Here's how I look at it. FLARM calculates a projected flight path with a probabilistic "error radius" determined based on flight parameters to estimate a likely future position (assuming no change in control inputs) and then maps these paths to estimate likely conflicts and warns if it finds one.. I consider that warning a prediction - if nothing changes the two aircraft will likely collide. Sure, it's an estimate but I still consider that more of a prediction than just putting airplane-shaped dots on a display and telling the pilot "you figure it out". I'd rather have a microprocessor and an algorithm than burying my head in a traffic display. I'd call that warning a prediction but maybe I'm being sloppy with the definitions.

The point is - FLARM will give you a warning only for pretty real threats. A traffic advisory system can only annoy you with constant warnings of aircraft in the vicinity whether they are a threat or not or leave it to you to find threats.by staring at a display. You need to project a flight path with some precision to strike a balance between too may false positives and leaving too many possible threats suppressed until too late. Given how we fly I think FLARM does quite well. It's also why ADS-B will struggle to operate as a collision warning system for gliders - even if someone tries to plaster a collision projection algorithm on top of some Garmin ADS-B unit. PowerFLARM throws out the ADS-B information if it detects a target with both FLARM and ADS-B Out.

9B

The discussion in this thread raises a significant question as to how much "predictive" information is actually transmitted as part of the FLARM protocol. I suspect that the differences in the information transmitted by FLARM and ADS-B are relatively minor.

I don't question the sophistication of FLARM's algorithms in filtering out collision threats that are real based on the trajectories of the aircraft in a soaring environment. Much of this processing must take place in the FLARM's receiver, as the trajectories of both the receiving aircraft and the threat aircraft must be known to determine if there is a collision threat..

My problem is with the assertion that a similar system can not be implemented using ADS-B. This is patently false. Numerous low cost iPhone and/or Android apps already provide collision threat warnings today using low cost ADS-B receivers. These apps not only report collision warnings for ADS-B equipped aircraft, but also for all transponder equipped aircraft that are identified by TIS-B received from an ADS-B ground stations (Note: You need to be ADS-B OUT equipped to reliably receive TIS-B traffic).

It is unlikely that these existing apps are optimized like FLARM is to recognize the unique flight profiles that are common with glider traffic. We will have to wait and see whether or not these companies will find it worth their while to invest in more sophisticated algorithms to specifically target the glider market. However, there are glider specific apps (iGlide, etc.) that are specifically aimed at the soaring market, which would have a strong marketing advantage in including this kind of advanced ADS-B based capability.

In Europe, given the large installed FLARM base, this may be an academic discussion. In the US, FLARM will never be widely deployed outside of the competitive soaring community. Here, an economical ADS-B based solution that provided reliable warnings, not only for other gliders, but also all other GA aircraft, would be a big hit.

Here we go again. Mike sharing his ignorance about powerflram with the world. Mike, each and every assumption and assertion you make is wrong. Maybe someone else will be willing to correct you on every wrong assumption, I wouldn't waste my time...