On Tuesday, May 26, 2015 at 4:44:07 PM UTC-7, Lucas wrote:
The T-Advisor AND Flarm are NOT anticollision system.
Anticollision systems are those who tell the pilot what to do (like TCAS), in case of emergency. Neither system does this.
BOTH systems are NOT anticollision systems.

This is a bit of a hair-splitting argument, but to be clear - there a 1) Traffic display systems (show traffic within a detection volume, but provide no alerts), 2) Traffic advisory systems (alert to new traffic entering a detection volume - like PCAS), 3) Collision detection systems (calculate and warn of other aircraft on a probable collision path - like FLARM), 4) Anti-collision systems (advise pilots on action to avoid a collision), 5) Automated anti-collision systems (autonomously take action to avoid collisions - I'm not aware of any of these - outside of military terrain-following autopilots).

Usefulness goes up as you move up the hierarchy. IMO FLARM, being higher that other systems is more useful.


Cleared this, those who talk about the "predictive algorithm", can please explain:

1) how it works, since they must know how it works, to be in the position of saying that it works or it doesn't

2) how they know that such an algorithm has been implemented into a Flarm system: what proof do they have of this ?

Really? That's a serious question? Well, it warns me of converging traffic and when I look, there is in fact converging traffic in the direction indicated. There is no traffic converging on me for which I get no warning and warnings for traffic that is not a series factor is almost nonexistent.


3) if they have ever seen the trace of at least 10 glider flights in different conditions (competition, cross country, around-the-airfield, ridge soaring,....); whoever has seen some, not many, traces of flights, without the need to be a glider pilot, can understand that a prediction of the position of a glider in a future time beyond a fistful of seconds is impossible, exactly IMPOSSIBLE, since not even its pilot knows it, apart from some cases, like straight flying and constant turn rate thermaling. A glider pilot knows that he will be changing the trajectory of the glider to search for the best netto value, which depends on the micro air movements, which are unknown to the pilot in terms of exact location. Is there a machine capable of predicting these locations ? And even if there was, is there a machine capable of predicting what a glider pilot will do in the next 30-60-80 seconds ? Because this is what the rumored (never verified) "prediction algorithm" does. This is spectacular indeed !

Impossible? As a control-systems engineer I can tell you for a fact that a 1 second sample rate is perfectly adequate for this purpose and you only need 2-3 good data points for each aircraft to make a decent prediction. Even with dropped packets this is a reasonable task. Glider flight dynamics are not so abrupt as to make this an impossible task and pilots are not generally making so many aggressive control inputs as to flail the system. FLARM uses a probabilistic approach base on total energy to err on the side of possible control inputs that handles most situations well.


4) even if they found a system to predict the position of the glider with a certain probability, would they trust as optimal a system that has (obviously) a probability to fail the prediction and miss a danger of collision ? Even if the probability was low (all but sure, since never demonstrated with objective tests and calculated data), 2, 3, 10 collisions (and deads) out of XX'XXX flights are too much. In aeronautics, this approach is wrong: this is not the way we work in professional aeronautics, that has taken us where we are in aviation

We don't need optimal, we need better than human perception and FLARM does that very well indeed.


9B