At 12:47 AM 11/11/2006, you wrote:
On Fri, 2006-11-10 at 10:12 +1000, Mike Borgelt wrote:
>
> 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.
That's the important point though for people considering opting in to
the FLARM system: if you have one, and 50% of gliders have them, you
have 50% effectiveness.
Effectiveness for what? Warnings? Or prevention of mid airs? Not
necessarily the same thing.
Somewhat less than 100% effectiveness against mid airs would be a
reasonable assumption.
Obviously if you don't have FLARM, it's not going to help you, so your
stats are misleadingly pessimistic there as you are assuming the chance
you have a FLARM is proportional to the entire fleet having one.
I thought I covered the assumptions quite adequately and note I was
talking about a group of ten who were potential collision risks and
the way the warning effectiveness changed with numbers fitted for the
fleet. I did also distinguish between the fleet risk and your
personal risk if you fitted a FLARM.
The invention of FLARM was driven by the problem in the European Alps
where there are hundreds, if not thousands of gliders flying out of
numerous sites, with pilots who speak different languages (even if
you speak the other guys language face to face it's much harder on
the radio - I found Texan was difficult for a few days) where the
radio is likely to be nothing but heterodyne squeal due to the number
of people on the frequency and of limited use anyway and where the
lift band is a narrow area close to the mountainside leading to
numerous 150 - 200 knot head on closing encounters with the pilots
spending a fair bit of their time and attention avoiding hitting the
mountain. Gliders closing head on at those speeds is a more difficult
problem than two Boeing 737's at cruise closing head on. Under those
circumstances I would expect a goodly reduction in mid airs between
gliders if FLARM is used. Note that this is also a case where there
are likely to be few powered aircraft who for now are not FLARM equipped.
This is a somewhat different situation from thermal soaring cross
country in a group over flat ground which is where 4 glider - glider
mid airs have occured in Oz in the last 10 years . Given the very
high false alarm rate FLARM has under the thermal joining/gaggling
cases and that these pilots had every reason to know there were other
gliders in proximity I have doubts that all of these would have been
prevented by FLARM.
What I find interesting is the radio chatter associated with FLARM.
"Do you see me?" " No but I think I've got you on my FLARM".
I wish I could believe that having the FLARM aid will free pilots to
look out for other targets but I fear that humans don't work that
way. The subconscious thinking will be "I've taken care of the
majority of the risk, the rest is very small, back to the PDA display".
The Avweb article I linked to had a few things to say about human
factors engineering as well as other things. I see PDA's in cockpits
obscuring important parts of transparencies and the discussion here
over the last few days about PDA's stopping is interesting. How good
is your lookout while being distracted by these? Carol calls them
Pilot Distraction Articles(PDA).
Mike
Borgelt Instruments - manufacturers of quality soaring instruments
phone Int'l + 61 746 355784
fax Int'l + 61 746 358796
cellphone Int'l + 61 428 355784
Int'l + 61 429 355784
email: [EMAIL PROTECTED]
website: www.borgeltinstruments.com
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