Pilots with weakening vision - please install Powerflarm

wrote, On 7/12/2013 4:54 PM:
That'sOn Friday, July 12, 2013 12:14:11 PM UTC-7, Dan Marotta wrote:

Now I won't mention any names, but what do you say to the pilot
who's installed a PFlarm but refuses to install a transponder?
Sure, he can see PFlarm equipped gliders, but neither TCAS nor PCAS
equipped aircraft, nor ATC can see him. To him I say, "Fine, I
respect your choice, now please respect mine." Even though I think
my choice is better.

Dan

I think that's easy - the number of fatal collisions between
transport-category aircraft and gliders is...drum roll...zero. So a
Transponder is a less valuable choice than PF for the average glider
pilot.

People are terrible at estimating low probability events - especially
catastrophic ones.

Three things:

- perhaps the probability is low because many pilots have already
equipped with transponders in areas where the potential for conflicts is
high. If that's true, we can not use the overall collision rate to
estimate the probability of non-equipped gliders colliding with
airliners and other large aircraft.

- even if we are poor at estimating low probability events, we are
perhaps good at estimating the cost of a catastrophic one. It won't be
just the loss of the pilot's life, but might involve potentially
hundreds of lives in the airliner and perhaps huge restrictions or costs
for all soaring.

- (Low probability) * (huge cost) = (makes transponder seem cheap) is
what a lot of us have calculated.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm
http://tinyurl.com/yb3xywl

On Friday, July 12, 2013 10:50:50 AM UTC-4, jfitch wrote:
I am surprised so far no one has noticed a serious flaw in my statistical argument.

Perhaps someone who understands statistics better than I do can clarify why the sample size that you use in your analysis is large enough to produce statistically valid conclusions. You've made an effort to gather and use all available data, and it sure would be nice if this were enough data to draw valid statistical conclusions, but do you really have enough data? People who understand statistics know how to answer that question.

And even if I accept your number, what does it mean to my purchase decision? The probability that you calculate would be too low for contest flying, and much too high for gliders flying XC in sparsely populated areas on weekdays. I would expect that the probability of a mid-air would be higher within a few miles of an airport, and much higher on a Saturday afternoon. If I fly in all of those situations, what number should I use? It seems like the probability of PowerFlarm saving my life in the most dangerous situation is the most prudent choice. (Is this why contest pilots feel that PowerFlarm is a bargain?)

My confusion about my personal cost/benefit goes deeper. If I buy a PowerFlarm and it saves my life, I would consider that to be the best $2000 that I ever spent. If I buy a PowerFlarm and it does not save my life, then I have wasted my money? No. If I buy a PowerFlarm as part of a community of glider pilots, and that collective action consequently saves the lives of a handful of glider pilots over a number of years, well hell, I'd still feel pretty dam good about spending that $2000.

We say that we don't want to spend money on something that does not benefit us directly, but then we feel good about being part of something that saves somebody else's life. Go figure.

Here's another question for our experts in statistics (and epidemiology).

Have you ever heard of 'Herd Immunity'? The idea is that you don't have to vaccinate everyone in order to stop the spread of a person-to-person communicable disease (for example, the flu). So a midair seems to be a lot like a person-to-person communicable disease.

Does Herd Immunity apply to the adoption of PowerFlarm? Surely we don't need everyone to adopt PowerFlarm to take a big bite out of mid-airs. When will competition pilots gain Herd Immunity from mid-airs?

On Friday, July 12, 2013 8:15:27 PM UTC-6, son_of_flubber wrote:
Here's another question for our experts in statistics (and epidemiology).



Have you ever heard of 'Herd Immunity'? The idea is that you don't have to vaccinate everyone in order to stop the spread of a person-to-person communicable disease (for example, the flu). So a midair seems to be a lot like a person-to-person communicable disease.



Does Herd Immunity apply to the adoption of PowerFlarm? Surely we don't need everyone to adopt PowerFlarm to take a big bite out of mid-airs. When will competition pilots gain Herd Immunity from mid-airs?

Addressing your two last posts.

Is there a herd immunity? Not unless mid-airs are contagious.

We have pretty good idea of the mid-air risk based on mid-air collision and number of flight data for the last 30 years without PF. In 30 more years, we'll have pretty good data with PF so then we can make a really good statistical statement on how effective PF is. Meanwhile, I take it on faith that the enhanced situational awareness afforded by PF is a very good thing especially in contests - and Texas.

Then there's an economic question of whether spending roughly $2000 to equip each of about 3500 gliders with PF is a sum that might be better spent elsewhere if the only goal is to minimize the overall number of serious accidents or the possibility of one really catastrophic glider-airliner mid-air that adversely impacts the whole sport. Some would suggest transponders are a better overall option in that case.

It is probably fair to say if you typically fly in airspace with a high density of airplane traffic, get a transponder. If you mainly fly in high density glider traffic, get PF. If both, get both. If neither, it's probably OK to wait for better technology. My guess is that when ADS-B is fully rolled out it will be the better option.

This posting is very much like the discussion we had at our club.
Our club has lost 4 planes and 3 pilots in mid-airs, 2 pilots have
survived using chutes.

At 18:24 12 July 2013, wrote:
Although Son of Flubber's post displayed a bit of youthful
arrogance, it
d=
id start an important dialogue. I would like to share a bit of
subjective
=
data that could add to the discussion. Regarding parachutes
as expensive
s=
eat cushions. I have had 5 friends and acquaintances bail out
of crippled
=
gliders and survive. Ghaham Thompson, Jim Indebro, Roy
Cundiff, and Dick
J=
ohnson among those lucky souls. Regarding mid air collisions as
highly
unl=
ikely events. In 1985 at a 15m nationals there were three mid
air
collisio=
ns, with one fatality. That represented about the same odds
as Russian
rou=
lette. Graham Thompson's bail out in Minden was the result of
a mid air.
=
Gary Kemp referred to Bruno's Gantebrink's essay on sailplane
safety. I
had=
a conversation with Bruno in New Zealand and he told me that
he was the
on=
ly surviving member, of five, of a previous German national
team.
Although=
, as I recall, one of the germans was killed after exiting the
glider on
th=
e ground by a piece of equipment. I have had two near
misses
(literally=
inches) where one of the pilots did not see the other before,
during or
a=
fter the near miss. I have had numerous close calls over the
years, so I
a=
m not impressed with those that say collision avoidance
systems are a
waste=
of money. Statistics are easy to skew and make this sport
look safer
than=
it is. The common thread with most the pilots mentioned
above is that
th=
ey fly, or flew, a lot, which, of course puts them at higher
risk.=20
I have O, none, no friends or acquaintances that have been
killed in
automo=
bile accidents. I would hate to count the number of glider
pilots that I
=
have known that have been killed flying gliders. Any!
procedure or
device=
that increases sailplane safety should be taken seriously.=20

DLB