At 09:11 AM 9/11/2006, you wrote:
I think it will happen one day - I think it is inevitable. But I also
think it is 20 years away. That might be pessimistic, but in other
ways it is also very optimistic :-)
FLARM has not been around long enough to have statistics to prove the
safety - therefore it is all predictions. It is a shame but that is
the way of life - we have to make a guess (albeit educated) then get
the stats.
However - it is statistics that show that most inflight glider
accidents are glider to glider - not other aircraft.
But we really need to squash this myth that you must have all
aircraft with them before there is increased safety. I am not sure
how that started but it is HIGHLY incorrect ! By all account it makes
no sense, statistically or logically. Every extra aircraft to have a
FLARM (flying in the same area of course) increases safety. Having
all would of course be a dream come true - but don't hold your
breath. Some gliders still don't carry radio and we know that adds to
safety. We will have aircraft in the skys for a long time without a
common collision avoidance - but it will be within most of our lives
that I think we will see that change :-)
Scott
Here's a simple analysis of the problem:
Suppose we have 10 gliders/tugs in this group. This would seem to be
a typical medium sized club situation on any given day.
Each glider/tug can collide with 9 others making 90 collision pairs.
However zero and one is the same as one and zero (and so on), so we
have 90/2 unique collision pairs = 45
If one glider is FLARM equipped then this is obviously trivial and
all collision pairs are effectively non FLARM 10% fit 0% effective
Similarly if all are FLARM equipped then 100% of the collision pairs
are FLARM equipped. 100% 100%
If 2 gliders are FLARM equipped only one pair is a FLARM pair which
leaves 44 non FLARM pairs. 20% 4.4%
If 3 Gliders are FLARM equipped 3 pairs are
FLARM 42
non 30% 6.7%
If
4 6
39
40% 13.3%
If
5 10
35
50% 22.2%
If
6 15
30
60% 33.3%
If
7 21
24
70% 46.7%
If
8 28
17
80% 62.2%
If
9 36
9
90% 80%
Notice that you need to equip over 70% of the fleet to reduce the
risk of a non FLARM interaction by 50%
Notice also how the number of possible interactions increases rapidly
with number of gliders. There's a lesson there about how many of your
mates you want to have a rat race with (or share a thermal with).
Note that your personal risk of a non FLARM interaction goes down
linearly as the percentage of FLARM equipped gliders increases if you
have a FLARM.
Note also the non FLARM equipped power traffic reduces the "% of
fleet equipped" number so the overall risk is as in the first table.
The only question is how many power planes are out there.
Mike
Borgelt Instruments - manufacturers of quality soaring instruments
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