Saturday practice at Hobbs NM

Am 22.06.2011 20:44, johngalloway wrote:
The diagram on page 12 of this Powerpoint presentation on the Flarm
website shows very clearly the situations in which Flarm is most or
least useful:

http://www.flarm.com/files/basic_presentation_en.ppt

In busy contest thermal gaggles with lots of Flarmed gliders there are
so many alarms that you often can't tell or see which other glider is
Flarming you and have to regard it as a serious ongoing prompt to
vigorous Seeing and Avoiding - in the knowledge that the other pilot/
will also be getting an alarm and will hopefully be doing the same.
That is very useful in its own way but it is a very different type of
situational awareness from the use of Flarm in the cruise or
approaching a thermal gaggle.

I think that even if a magical Flarm were able to produce positional
and conflict information with zero error it would be impossible to do
much better for the case of busy similarly centered gaggles because
the gliders are continually making unpredictable centering and
avoidance corrections.

John Galloway

I had the pleasure of flying in a contest recently where all planes
were equipped with FLARM. Having several years of experience with flying
FLARM equipped gliders both in X/C and contest gaggle situations, I have
the impression that especially in gaggle situations the FLARM algorithm
has improved a lot with the current software version 5.xx. I had almost
no false alarms, and a few positive alarms in situations where an alarm
was appropriate.

I encountered one situation where I had no alarm, although the situation
might have developed into a close approach. This was a situation where I
was flying vertically underneath of another glider, with the vertical
distance becoming smaller. This is one of the "weak spots" because of
the usual position of the FLARM aerial the view below the aircraft is
obstructed. As the other glider was clearly visible, there was no real
danger though.

In the course of that contest, I had one situation en route where FLARM
provided important additional information. I already had spotted one
glider that was approching me on the same height in my 12 o'clock
position, and made a slight movement to the right. At that moment, the
FLARM was going off, showing me that there actually were two targets
approaching me. Scanning the horizon again I spotted the second plane,
and we all were able to pass each other in safe distances with very
little corrections of our course.

FLARM has its limitations, but it certainly can help to avoid dangerous
situations by giving the pilot additional informations on top of the
close lookout.
--
Peter Scholz
ASW24 JE