On Wednesday, May 2, 2018 at 6:57:19 AM UTC-7, Tom BravoMike wrote:

I second your opinion. With all its obvious merits, FLARM is glider-specific. It's not seen by the GA participants.

And BTW, if everybody is so concerned with the safety (including the FLARM people), how come we don't have inexpensive FLARM receivers on the market? Why can I get a cheap, under $100, ADS-B-in devices and follow the traffic through all kinds of apps, without having myself (yet) an ADS-B-out? Why can I get a TCAS or PCAS which informs me about transponder equipped planes around me - but no FLARM signal receivers which could show the targets on XCSoar even without the PowerFlarm in my ship?

Or maybe I'm wrong? Please correct me, let me know what cheap FLARM receivers are out there, and I will be happy to start my experience with the FLARM signals and increase safety, say by 20-50% ...

in order for flarm to predict a potential collision, it needs BOTH aircraft to be transmitting information. a receive only flarm would give situational awareness, but NO collision avoidance.

Matt, could you please expand on it or direct me to a source so that I can understand better (and appreciate) how FLARM works? Is it about hardware (e.g. directional antennas) or software algorithm? My flight data is on board in my glider - right?, and from the 'receiver Flarm' I would get flight data transmitted from other gliders. What prohibits MY computer to do the needed calculations (course, speed, altitude) with regards to a potential collision? Isn't that what the existing apps for the cheap ADS-B-In are doing? I can see other aircrafts with their speed and direction, and as they get closer they change the color from blue to yellow to red and at one point alarm goes off. Why do you 'have to transmit' to receive this kind of a warning?

Thankfully we don't have FLARM receive only boxes... well not mainstream ones anyhow. To provide good defense across to the fleet we need lots of gliders equipped with transmitters. The sensible choice was for FLARM to focus on delivering boxes that did both and for the glider fleet to equip with both capabilities, and for the system to be relatively simple and work.... ADS-B set out to be relatively *complex* and is a bit of a mess because of that. FLARM is relatively simple and *should* just work, at least compared to ADS-B... Unfortunately the PowerFLARM rollout in the USA hit too several snags and was painful for a while, hopefully those issues are well behind us..

GA and ADS-B In in the USA is a model of what could happen by delivering low-cost receive only devices. We had lots of folks buying UAT or dual-link low cost receivers over the last half decade or so. With many of those GA aircraft not equipped with any ADS-B Out, so the effective coverage was not great and there has been a fair amount of confusion about what services a non-ADS-B Out aircraft receives that lulls some pilots into a false sense of security about what they are receiving.

FLARM choose to encrypt part of their data, which makes third parties doing stuff with the data difficult. That provides FLARM protection against competitors but also allows FLARM to ensure their systems are all compatible. Lots of the mess with ADS-B is trying to meet requirements/needs from so many potential users, and just trying to spec requirements which gets complex fast. FLARM has been able to avoid much of that by focusing on the glider market (and yes they do some GA in Europe and are doing more drone work now) and picking specific components/technology parts (FLARM actually makes some of the internal chips and firmware used on them and is very careful about the specific GPS technology they integrate with) and using in their systems.

Some of the questions above has been gone over before on r.a.s. and makes me think you have not flown with FLARM and not really compared it to an ADS-B based traffic system. The basic description of seeing traffic icons is kind of pointless, gliders are often surrounded closely by other gliders, nobody should be looking at the screen to see if they think they might run into another aircraft or relying on coarse 'traffic' audible warnings which rapidly become distracting, and need to be silenced. None of those other systems work well in the environment of other gliders and towplanes in close proximity, and they are simply not designed to.

At the most basic level FLARM is transmitting GPS data and looking at other FLARM units GPS data.... the antennas are not directional etc. It's all about software and focus on the glider community and making the traffic warnings usable/reducing false positives and providing the NMEA based data integration with glider traffic displays and glider flight computers... nothing those other systems can do. But to do that as well as FLARM does is non-trivial. Would it be nicer for PowerFLARM to be lower-cost, sure, but I also could not think of the effort needed to develop that technology and ecosystem and sell a similar system into such as small market (tens of thousands of FLARM units being a small market).

There are technical resources online about how FLARM works, findable with a Google search, but I suspect you would probably be better off flying a PowerFLARM equipped glider and see how FLARM works for you. If you have PowerFLARM users in your area then ask them, it would be fairly unusual for folks who have it not to recommend it. If nobody has it in your area then it's kinda academic unless you want to start a campaign for other folks to install it.

FLARM can be a great tool, but to provide technology assisted traffic awareness and collision avoidance owners/pilots might need to consider FLARM, Transponders, ADS-B Outf, ADS-B In and what works best for their specific threat scenarios.