Michael,

Your experience vis-a-vis how NTSB accident numbers (reported) stack
up compared to the actual total number of accidents (reported +
unreported) is not at all unusual. I too know of numerous unreported
accidents. But this isn't peculiar to aviation -- it probably happens
in a lot of different settings and more often than we realize. That's
what makes estimating and/or extrapolating accident information so
difficult. Perhaps if we always stated a number plus-or-minus some
estimate of the error that'd be satisfactory?

Again, my intent was to try to establish some kind of broader context
for the numbers, imprecise as they may be, unknowable as they may be.
Regarding the accident pyramid applied to aviation, see Diehl, Alan E.
"Human Performance and Systems Safety Considerations in Aviation
Mishaps," The International Journal of Aviation Psychology, vol. 1,
no. 2, pp. 97-106; see also Veillette, Patrick R., "Not All Spins Are
Equal," University of Utah, 1986 (notes from a presentation).

"Relatively few" is the 1 accident per 331 (or X) total hazardous
encounters.


(Michael) wrote in message . com...

I would disagree thusly: the pilot who does not routinely ("routinely"
meaning at least 50% of the time) simulate an engine failure followed
by a glide to landing (even from abeam the numbers would be
beneficial) is equally as likely not to be able to handle an engine
failure to a successful landing (i.e.: no accident) as a pilot who
allows the development of an inadvertent stall/spin.

See, this is another example of a hypothesis (I would not even
consider it a theory) that won't stand the light of day. Where did
you come up with 50%? Are you suggesting that a pilot who only makes
20 landings a year (hardly unusual, given how little most private
pilots fly), of which 10 are simulated engine failures, will do better
with a real engine failure than a pilot who makes 300 landings a year,
of which only 30 are simulated engine failures?

It only makes sense that those who don't practice power-off landings
are less likely to be able to competently perform them when necessary,
but going from that to hard numbers without additional evidence is
simply not reasonable.


As a flight instructor charged with the task of educating pilots and
(hopefully) offering them guidance in terms of how often to practice
certain procedures/maneuvers on their own, what frequency do you
recommend in this regard, and on what is that recommendation based? My
suggestion to practice gliding approaches to landing on the order of
50% of the time is based on my anecdotal experience flying with
licensed pilots in the EMT Program, including performing 14,000+
landings, the great majority of which have been gliding approaches in
many types of light airplanes.

I think we'd agree that the number of such practice approaches is
somewhere between 0 percent of the time (airline-type flying) and 100
percent of the time (gliders). Also, and though it hasn't been stated
explicitly, I'm talking in terms of the "average," "typical," "normal"
pilot flying the typical light airplane on a typical flight. That
said, I do believe that an average pilot who performs 10 gliding
approaches out of the 20 approaches annually will be likely to react
appropriately to an engine failure. Now, because this pilot may lack
the breadth of experience of your atypical 300-landings-per-year pilot
who practices gliding 10 percent of the time, the less-experienced
pilot (but who is more representative of the norm) may not be as
precise overall, yet the fundamental skill set needed to cope should
be there nonetheless.

In fact, typical pilots under duress will invariably only be able to
perform as well as their most basic skill set allows. And those skills
that are the most practiced, the most familiar, the most "natural" to
the pilot are the ones that will largely determine the outcome. Again,
this is based on my anecdotal experience instructing 1,000's of pilots
while they are placed under duress during emergency maneuver training
-- typical pilots from across the country who are representative
"products" of our national flight training system.

Also based on my experience, the dominant experience and instincts of
the 300-landings-per-year pilot who practices glides 10 percent of the
time are not those consistent with gliding, but are those consistent
with powered approaches. Such a pilot may actually have to fight
harder against the natural urges/tendencies developed and reinforced
during all those powered approaches.


I don't believe a stall-spin involves a typical pilot at all.

The numbers and the anecdotal experience of professional
spin/aerobatic flight instructors are totally at odds with your
belief. The typical pilot is trained by the typical flight instructor,
who himself/herself has a marginal understanding of, and marginal
practical experience with, anything related to stalls and spins and
therefore, is incapable of adequately providing stall/spin awareness
training to their students. See "Re-Examination of Stall/Spin
Prevention Training," Transportation Research Record, No. 1379,
National Research Council, Transportation Research Board, 1993, by
Patrick Veillette.

Anecdotally, I see it firsthand every day either flying with, or
providing stall/spin seminars to, typical pilots from all around the
country -- again, they are representative products of our national
flight training system. Moreover, the statistics in every way point to
typically-trained pilots on typical flights: NTSB's special study
covering the years 1967-69 showed that 1/3 of stall/spin accidents
involved pilots with more than 1,000 hours of flight time. The median
pilot experience of those involved in stall/spins was 400 hours.
Though even higher time pilots succumb to stall/spin accidents, we can
profile who is most at risk of an accidental stall/spin as follows:
it's the pilot who has logged fewer than 1,000 hours; who is on a
daytime pleasure flight in good weather; who is in the traffic
pattern; and who is either turning or climbing. Leading up to the
inadvertent stall/spin, the pilot will be distracted into making a
critical error in judgment. Fixation on the unfolding accident will
effectively render 1 in 3 pilots deaf to the blaring stall warning
horn. And pilots with fewer than either 500 hours total time, or 100
hours in type, are more likely to encounter an inadvertent stall/spin
than to have a genuine engine failure.

Consider the following 1987 stats as well: the U.S. boasted 699,653
active pilots who collectively logged an estimated 47.9 million flight
hours. Amortized, pilots averaged 68 hours each that year
(unfortunately, this average had decreased to less than 50 hours per
pilot per year during the 1990's). Consider, too, that the average
active flying career of a general aviation pilot is estimated to be 17
years. Hence, the typical pilot will accumulate close to 1,200 hours
total time. The majority of pilots--students, private pilots,
CFIs--remain squarely in the bull's-eye of the stall/spin accident
zone throughout their aviation careers. They are the ones encountering
accidental stalls and spins, most of which are just hazardous
encounters, some of which result in accidents.


As for mid-airs, during the period 1977-1986, 40 percent of the
mid-airs ended without injury.
So my estimate of a minimum 25% fatality rate for midairs (3:1)
doesn't sound too far off. Certainly 1:30:300 is not a good fit.

Somewhere, somehow the discussion shifted from "total accidents" to
"fatal accidents only." The 1:30:300 is all hazardous encounters
leading to all accidents, not total accidents vs. fatal accidents vs.
some-injury accidents vs. non-injury accidents. Regarding mid-airs,
the question would be, "for each mid-air, how many times are airplanes
coming close enough to each other to be considered a hazardous
encounter (especially when pilots in both airplanes have their heads
buried in the cockpit on a clear VFR day)?" Maybe 331 times as many as
the total number of mid-airs that resulted in accidents (whether those
on board were injured, killed, or not)???

Rich
http://www.richstowell.com