Glider Safety

It also means that over a 40 year soaring career your probability of
being in a fatal accident is around 1 in 50, or 2% - assuming you fly
the average annual amount of hours over the entire period.

9B




No, it doesn't. The risk isn't cumulative, it's 1:2,000 each year you fly.

I can guarantee that if you have a fatal accident in year 1, your risk
of repeating it in years 2-40 is 0%.

Bear in mind also that more than 3/4 of fatal accidents seem to have
causes within the pilot's own control so that, if you flew perfectly all
the time, you could reduce that risk to more like 1:8,000.

My philosophy is that 1:2,000 is acceptable, and that I will work to get
it nearer 1:8,000. Still more dangerous than autos per hour, but worth it.

Chris Reed wrote:
It also means that over a 40 year soaring career your probability of
being in a fatal accident is around 1 in 50, or 2% - assuming you fly
the average annual amount of hours over the entire period.

9B


No, it doesn't. The risk isn't cumulative, it's 1:2,000 each year you
fly.
True, but 9B said "over 40 year soaring career".

I can guarantee that if you have a fatal accident in year 1, your risk
of repeating it in years 2-40 is 0%.
True, but irrelevant. I also calculate the risk over a 40 year period as
being 2%, assuming the 1 in 2000 chance/year. YMMV.

Chance of not being in an accident each year = (1 - 0.0005) = 0.9995
For 40 years, chance = 0.9995^40 = 0.98

That's 98% chance of not being in an accident. Lots of assumptions, so
maybe not too instructive.
For 40 years, 1 in 8000 gets it down to 99.5% of not being in an accident.

--
Eric Greenwell - Washington State, USA (netto to net to email me)

- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm http://tinyurl.com/yb3xywl

- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what you need to know tinyurl.com/yfs7tnz

Eric Greenwell wrote:
Chris Reed wrote:
It also means that over a 40 year soaring career your probability of
being in a fatal accident is around 1 in 50, or 2% - assuming you fly
the average annual amount of hours over the entire period.

9B


No, it doesn't. The risk isn't cumulative, it's 1:2,000 each year you
fly.
True, but 9B said "over 40 year soaring career".

I can guarantee that if you have a fatal accident in year 1, your risk
of repeating it in years 2-40 is 0%.
True, but irrelevant. I also calculate the risk over a 40 year period as
being 2%, assuming the 1 in 2000 chance/year. YMMV.

Chance of not being in an accident each year = (1 - 0.0005) = 0.9995
For 40 years, chance = 0.9995^40 = 0.98

That's 98% chance of not being in an accident. Lots of assumptions, so
maybe not too instructive.
For 40 years, 1 in 8000 gets it down to 99.5% of not being in an accident.

OK, I'll accept that as a calculation at the beginning of year 1.

However, I've survived 14 years without a fatal accident so far. In the
remaining 26 of my 40 year career (I hope), that gives me a 0.9995 to
the power 26 chance of a fatal accident (0.987, or a 1.3% chance). If I
make it to the end of year 39 I have a 1:2,000 or 0.0005 chance of a
fatal accident in the final year.

I don't think the probability over a flying career helps understand risk
much on an individual basis, though it's useful for insurers and actuaries.

Much better to think that you have a 1:2,000 chance in the coming year,
and work on getting that ratio to improve in your favour.

I wonder how these calculations take into consideration the hours spent on both activities. After all, one spends a lot more time driving than flying a glider (although there may be a lucky few for whom this does not apply).

Perhaps I have been sheltered,

But I have never heard the claim the flying gliders was safer than
driving.

What I have heard and my amateur review of the fatality numbers per
hour seems to confirm is.

Flying commercial airlines is safer than driving.

GA flying about the same as riding a motorcycle

GA flying can be as safe as driving if you eliminate low flying and
bad weather flying.

Glider flying is more dangerous than GA flying, I am unsure by what
factor.

*************
Of course there are many ways to look at the numbers. One can count
fatalities, injuries or accidents. One can count per vehicals or per
person. Just those two variables give about 12 different
combination's of ways to count the numbers,

However I am looking forward to Tom's Analysis.

Brian
CFIIG/ASEL

On Feb 22, 5:19*pm, michael case wrote:
Of course there are many ways to look at the numbers.

My favourite are the pair of statistics from the '70s, probably
still true today:
1 landing in commercial airliners is becoming safer
2 landing in commercial airliners is becoming more dangerous

1 is true for accidents per landing
2 is true for proportion of accidents while landing

On Feb 22, 10:19*am, michael case wrote:
Perhaps I have been sheltered,

But I have never heard the claim the flying gliders was safer than
driving.

What I have heard and my amateur review of the fatality numbers per
hour seems to confirm is.

Flying commercial airlines is safer than driving.

GA flying about the same as riding a motorcycle

GA flying can be as safe as driving if you eliminate low flying and
bad weather flying.

Glider flying is more dangerous than GA flying, I am unsure by what
factor.

*************
Of course there are many ways to look at the numbers. One can count
fatalities, injuries or accidents. One can count per vehicals or per
person. *Just those two variables give about 12 different
combination's of ways to count the numbers,

However I am looking forward to Tom's Analysis.

Brian
CFIIG/ASEL

Statements like "safer than" or "more dangerous than" are not
extremely useful. The statistical base for pilots, and the quality of
those statistics, is too small and sketchy to meaningfully compare one
activity with another.

Safety in the air depends almost entirely on the individual pilot
whose attitude, self-discipline, skill-set and knowledge determine the
level of safety for that pilot. Statements to the effect that
"soaring is dangerous" serves a useful purpose only to the extent that
it encourages individual pilots to acquire those traits and practice
safe behavior.

A more meaningful approach would be to discuss how we individually
can safely manage an unforgiving system. Soaring is certainly
unforgiving of any neglect or carelessness - Individually, we need to
learn how to manage those risks. It might be correct to say "soaring
is extremely dangerous for careless, neglectful pilots" but is
relatively safe for "careful, disciplined pilots".

I believe that the statement "Soaring is Dangerous" may be useful
statement to say to certified pilot but it certianly isn't what you
want to say to a 14 year old's Mom just before they take an intro
flight.

The statement "Soaring has it Dangers/Risks as does any Activity" is a
better statement, better still the statement that "the pilot has huge
amount of control in how risky a flight is or is not" is even better.

An indepth statistical analysis would take the 12 combination's of
variables i listed above (accidentally posted as michaelcase")
compared to other activities. However has Tom has already mentioned
it is difficult to get accurate numbers especially when you start
talking about incidents without injuries.

But it is useful to compare it to other activities since this is no
standard Risk level scale. It would be nice if we could says Soaring
rated a 6 on risk scale. But even then we would compare it to other
how other activities rated on the same scale. The benefit is it helps
pilot realize that they need to be diligent to keep it safe and helps
uninformed people make a decision about how much risk they willing to
accept.

The person riding to the airport on their Harley is probably less
likely to consider soaring too risky than the person who drives their
Volvo to the airport.

Brian