How I Learned to Stop Worrying and Love the Bomb

Frank,

On Friday, January 17, 2014 10:38:48 PM UTC-5, Frank Whiteley wrote:

1/3333 beat the odds. 2007, 6, but one was most assuredly a suicide, so a skewed factor,
thus 5 is the acceptable number. Again, we're at 1/2000. 1/1800 just kind of looks about
right given what we know about the pilot population. The number is likely better than overall
odds of traffic, ladders, being a pedestrian, or cleaning the gutters, etc.

There's an article by Tom Knauff that comes up with very similar numbers:

http://www.eglider.org/NewsArticles/...mergencies.htm

Now, the thing is, coming up with informative statistics is difficult in this context, and it is difficult to put these statistics into perspective for the average glider pilot or person potentially interested in gliding.

As for the latter, a lot of this has to do with the fact that people are notoriously bad at judging and handling probabilities of rare events. No disrespect to anyone here. (I make my living by doing university research into people's cognitive "in"abilities, and people's mistakes in decision-making are very well established.)

Second, I would point out that while the probability of dying seems acceptable, risk (and "expected utility") has a second component: the cost in the event that something does happen. Many of us have lost a friend in a gliding accident. It was after I talked to the dad who lost his twenty-something year-old daughter (and my friend) in a gliding accident, that I understood what such fatalities mean to one's family, friends, club mates, workplace, and so on. I think we might underestimate this, and the numbers don't really do this any justice.

As for the statistics, I wish we could express the probability of a fatality per glider flight. If we assume 11,000 SSA members and 6.7 fatalities in the US annually, how many flights do people do, on average? If it's 20 flights (given that many people don't fly much), I get to 30 micromorts. The right way to do this would be to survey logged hours (ensuring random sampling and an acceptable response rate), and count accidents for sample population (i.e., sample from SSA membership, and count only SSA-member accidents). I think that the OLC database might be a good population, provided your result then applies to people enthusiastic and experienced enough to log their flights there.

I want to point out that risk expressed in terms of number of flights or flight hours is also difficult to interpret, because the relationship between flights and total risk is not linear. Highly inexperienced, not-current pilots are likely to be less safe. Very high-time pilots might also be less safe, as they would tend to fly in a broader range of conditions and over other terrain. That's why I would call the "10-years of risk equals 10 times .18 probability" perhaps a back-of-the envelope approximation, but also armchair statistics.

Gliding brings plenty of long-term health benefits as well. Many of us are 70 y/o and pretty fit, physically and mentally. Self-selection or causation? I don't know. We're not taking this into accounts so far.

A much more informative estimate might be one's individual assessment, or even our assessment of the other guy rigging his glider. Am I fit to fly today? Have I checked those control connections? Am I diligent with checklists? Do I know the weather? Am I current? And so on.

All of that said - nothing is a "safe" activity. We're all going to die of something. The question is: when that day comes, have we lived?

On Saturday, January 18, 2014 9:55:20 AM UTC-8, son_of_flubber wrote:
On Friday, January 17, 2014 10:38:48 PM UTC-5, Frank Whiteley wrote:

1/1800 just kind of looks about right given what we know about the pilot population.



Thanks for this well-considered number, it completes the picture. To relate it back to the context of my original point...



1/1800 equates to a .18% chance of glider related fatality in each year of flying. Over ten years that would be .18 X 10 = 1.8% cumulative risk over 10 years (say 2%).



Side by side with my original mortality prognosis (individual based on my age and health status):



I have a 19% chance of dieing from all other causes in the next ten years..



I have a 2% chance of dieing in a glider in the next 10 years.



Say a 10:1 chance of dying of natural causes before I die in a glider. I'm good with that, but I will keep looking for ways to improve my odds.

Our club got into this topic a couple of years ago regarding the old statement of the drive to the airport being the most dangerous part of a glider flight. I went about the analysis a little bit differently, but came to about the same number for gliding. Per the NHTSA statistics, in 2011, auto fatalities were 15.28 per 100,000 (1/6,545) licensed drivers. Using this set of data leads to a 0.015% chance of becoming an auto fatality statistic. Bottom line is that flying a glider is more dangerous than driving a car, but in a risk/benefit assessment, the risk of gliding is (generally) fully acceptable, and the benefits (enjoyment, challenge, etc) far more than offset the risk. Similarly, auto fatality statistics apply to the average commuter, not race car drivers, who have their own risk/benefit analysis which leads them to accept a higher risk for participating in their sport.

The risk of a fatality is not the same as the likelihood. We expose ourselves to the risk of an auto fatality much more frequently than we do to a gliding fatality. For the auto side, there is a low risk, which coupled with the frequency still leads to a low likelihood of a fatality. For soaring, the risk is much higher (although still low), and the frequency of exposure is less. I haven't worked out the likelihood for soaring, but it is probably less than the risk might lead one to think.

Of keen interest to me, just recently having cataract surgery, the risk of a major complication from the cataract surgery, up to and including blindness, is about the same as a soaring fatality (in the analyses overall). Having had the surgery, I wouldn't try to keep flying without having it, now that I know the impact of cataracts on vision. Likewise, so long as I take care of pre-flight, in-flight and post-flight tasks in a safe manner, I'm confident that risk of a fatality while flying remains low - for me. Not wanting to judge, I've watched other pilots do - or not do - things that makes their risk of having an accident, fatal or not, much higher than 1/1800. (Note: the risk of a group is essentially an average for that group. For some members, the risk is much less, and for others, much higher. So, for one pilot the risk might consistently be 1/500 and for another 1/2500. And, the risk can vary from flight to flight, depending on a number of factors. Bottom line - the averages help, but don't tell any one pilot what is going to happen any one time, or over their flying career.)

It is interesting to note that since 1994 the auto fatality rate has been consistently declining primarily related to auto and road safety measures, not better driving habits or heightened driver safety awareness. Maybe a message there for soaring safety, maybe not, since so many fatalities occur on takeoffs and landings. But driver error is as a contributor to auto fatalities, and some auto safety improvements have led to fewer fatalities regardless of driver error.

Another 2 cents worth.

On Saturday, January 18, 2014 9:55:20 AM UTC-8, son_of_flubber wrote:
On Friday, January 17, 2014 10:38:48 PM UTC-5, Frank Whiteley wrote:

1/1800 just kind of looks about right given what we know about the pilot population.



Thanks for this well-considered number, it completes the picture. To relate it back to the context of my original point...



1/1800 equates to a .18% chance of glider related fatality in each year of flying. Over ten years that would be .18 X 10 = 1.8% cumulative risk over 10 years (say 2%).



Side by side with my original mortality prognosis (individual based on my age and health status):



I have a 19% chance of dieing from all other causes in the next ten years.



I have a 2% chance of dieing in a glider in the next 10 years.



Say a 10:1 chance of dying of natural causes before I die in a glider. I'm good with that, but I will keep looking for ways to improve my odds.

I agree with your math for us old geezers, but if you run the numbers for a 20 years old for their risk of dying in a glider vs natural cause? I bet the results will not be too encouraging...

Ramy