These seem to me to be two examples of difficulty assessing the number of decimal places in looking at probabilities.

Equipping a towplane with UAT says an owner is willing to spend money on ADS-B, but not the flavor that represents the vast majority of collision threats (it's a glider towplane after all). That just seems dopey. UAT is problematic for other reasons too in that it requires ADS-R or a dual-band receiver to be seen by the vast majority of aircraft that have opted for 1090ES and towplanes tend to operate down low where ADS-R services may not be available for other powered traffic. A waste of money that simultaneously makes other people's lives less safe and more difficult. Buying something that's far less likely to work because it's cheap hardly seems like a smart buy.

I doubt that Flarm would pick an algorithm that can both identify what's a towplane through formation flight and then blank out the ADS-B ICAO address and never check for towplane behavior again - but even if it did the probability of a towplane releasing a glider and circling around in a climb to become a collision threat seems like and extremely low probability scenario and not a reason to reject/critique the idea of towplane suppression. In 46 years of glider flying I've never, ever seen a towplane do that. Either way towplane suppression is a good idea and I tend to think the Flarm folks are pretty clever. I look forward to trying it out.

Andy Blackburn


On Tuesday, March 19, 2019 at 8:44:42 PM UTC-5, Mike Schumann wrote:
skyBeacon is a pretty darn inexpensive and easy to implement way to make a tow plane 2020 compliant. I wouldn't be surprised if a significant number of people don't go that route, even though it is UAT instead of 1090ES.

A big question is exactly how FLARM has suppressed the tow plane ADS-B alarms. Does FLARM recognize the fact that the tow plane and glider are in formation, and only suppress the alarm while the formation flight continues, or does it somehow completely suppress all alarms for the tow plane? You definitely would want to see tow plane alarms after the glider releases from the tow in the event that you accidentally get on a collision course with the tow plane after the completion of the tow.