On Aug 9, 10:29*am, Mike Schumann
wrote:
On 8/9/2010 11:57 AM, Andy wrote:

On Aug 9, 9:45 am, Mike
wrote:

Why not require ADS-B units instead. *Then you'd get the advantages of
FLARM, but you'd also see all of the transponder equipped GA aircraft
(assuming that there was a ground station in the area).

Perhaps because glider pilots would be overwhelmed by nuissance alerts
when contest flying? *I have already experienced my PCAS becoming
close to useless as more gliders are fitted with transponders. *I
don't need another system crying wolf all the time.

FLARM uses intelligent alerting based on glider flight
characteristics. *It has been reported that the nuissance alerting
frequency low enough that it is still useful in high glider traffic
densities.

Andy

There are two parts to FLARM; *an ADS-B type position reporting
broadcast function, and a built in collision warning system.

ADS-B transceivers typically do not include any collision warning logic.
* Instead they are more like modems. *They transmit and receive position
data in addition to receiving weather info, etc. *This information is
passed on to some form of graphics display device so that the locations
of other aircraft can be shown on a moving map display relative to your
own aircraft.

The display device, in addition to showing the location of other
aircraft, can also be programmed to provide collision warnings.
Obviously, the typical flight trajectories of gliders are different than
most power aircraft. *I suspect that most glider specific moving map
vendors will try to match FLARM's logic to minimize false alarms if they
elect to provide a collision warning function in addition to just
displaying the relative locations of other aircraft.

ADS-B is obviously just in its infancy in the US vs FLARM's development
in Europe. *The encouraging news is that the potential size of the US
ADS-B market is much larger than the potential FLARM market in Europe
(when you include the GA power market), so there will undoubtedly be
lots of innovation in the display devices that will provide the
collision warning function. *In VFR environments, these devices will not
require FAA approvals, so I expect that technical advancements will be
very rapid, once low cost ADS-B transceivers become widely available.

--
Mike Schumann

Andy raises a specific good point, that there is no current answer to,
except hand waving and hoping. So to be clear, there is no ADS-B
product (besides the soon to be PowerFLARM 1090ES receiver) that is
optimized for glider threats/traffic warning. None. Nada. Zilch. And I
expect false alarms to be a significant issues with current ADS-B
systems especially in busy gaggles - one of the times that many glider
pilots worried about glider-on-glider threats may be most interested
in usable collision avoidance warnings.

Until we have an ADS-B products specifically targeted at the needs of
glider cockpits they are unlikely to successful in this market for all
the reasons I've pointed out elsewhere in this thread. Glider pilots
worrying about glider-on-glider and glider-on-towplane type collision
scenarios may not be that well served with a traffic display/warning
system developed for GA aircraft, especially in contest scenarios. It
will likely have all the false alarm issues Andy is raising. Somebody
with a focus on delivering a product to the glider community has to
develop that system, whether (ideally, for reasons pointed out
elsewhere in this thread) it is within the ADS-B transceiver/receiver
product or within an external display product. Then your claims about
market sizing and innovation just flip on their head. The potential
size of the USA market for people who want ADS-B transceivers/
receivers in their glider cockpits is smaller than the size of the
existing worldwide (not just Europe) Flarm market.

Darryl