Real stats on engine failures?

Sorry for the tone but it is incredible to me that anyone thinks that
changing oil protects against structural failure of a crankshaft or
connecting rod. Yes changing the oil makes the bearings, gears, cam/lifters
and all other rubbing/sliding parts last longer but it does not affect
cracking one bit.

Mike
MU-2


"Tom S." wrote in message
...

"Mike Rapoport" wrote in message
link.net...
Presumably you have never worked on an engine at all.. Please describe
how
changing engine oil keeps a connecting rod from breaking in half.


Please lose the patronizing tone that you came into this discussion with,
then I'll continue with my QUESTION. (No wonder that one guy said he came
into the group, then left after seeing the abuse some dole out.)

"Mike Rapoport" writes:

But do you agree that components that require maintenance (propeller,
cylinders, engine mounts, ...) can cause/accelerate crankshaft
failures?

I suppose that I agree to a limited extent, but virtually all
crankshaft/connecting rod failures are caused by a flaw/fault in
design/manufacture or installation. Once the crank or connecting rod is
installed, nothing is done to it and it is unseen until overhaul time. A
failure of either of these components is not going to put much, if any,
metal into the oil until the bitter end either..

I was thinking less of metal in the oil than the forces exerted on the
crankshaft. An out-of-balance prop or even a faulty spark plug can
cause out-of-spec. impluses to be exerted on the crankshaft.

I sure don't know how significant that is likely to be though. ('course
you can consider the stories of pilots taking off after prop. strikes as
an extreme.)

--kyler

(Rich Stowell) wrote
Geez Michael, settle down! So much stress in the cockpit cannot be
conducive to learning or safety...

I don't know about you, but I'm not in the cockpit when I post.

Interesting that I cited a specific source for my statement, which you
summarily ignore as either irrelevant or incapable of leading to
numbers that might be relevant to the concerns that started this post.
Have you read the study I cited?

Yes. It provided no sources on actual engine failure statistics.
Accident statistics are not the same thing at all. Engine failure
statistics from other than GA light piston airplanes also don't cut
it.

If it "hideously skews the picture" wouldn't that apply to all
accident numbers from NTSB?

Yes. NTSB numbers are not a valid way of estimating how often any
event occurs, unless that event always results in an accident or
incident. Actually, my experience with NTSB investigations of light
GA crashes leads me to believe that they're not good for anything at
all.

Each stall/spin accident represent the tip
of the stall/spin problem. Each engine failure accident represents the
tip of the engine failure scenario. Accident stats are a poor measure
of our overall stall/spin awareness, and of our ability to cope with
engine failures precisely because accident numbers represent the
relatively few pilots who have had an accident.

Now there's something we can agree on.

BTW, how do you define relatively few?

But useful information can be gleaned.

Not about the actual rate of incidence of any type of hazard, nor
about relative rates of incidence of various hazards.

Define "rarely." From an industrial accident prevention standpoint,
the theoretical ratio 1:30:300 is often applied wherein for every 331
hazardous encounters of a similar type, only one will progress as far
as an actual accident (significant damage and/or injury). The rest
fall under "incidents" and "hazards."

That ratio is nothing more than an expression of ignorance. In
reality, depnding on the hazard the numbers can be very different.


You neglected to define "rarely."

Consider it equivalent to your definition of "relatively few."

And which "numbers" can be very
different -- total numbers, ratios, what?

In this case, I specifically mean the ratios of accidents and
fatalities to total occurrences. The only numbers we REALLY have are
fatalities - a fatality is difficult to cover up, and thus I would
imagine all (or nearly all - say 98% or better) of fatal accidents are
reported and wind up in the NTSB reports. Non-injury accidents are
often not reported - I know of several where the owner did not have
insurance and did not want to bother with reporting anything. Yes, I
know this is a vilation of NTSB 830. BTW, that includes an engine
failure accident where the airplane was almost completely destroyed.

Granted, total raw numbers
can be significantly different between different accident types,
but--as the study of industrial accident prevention postulates--they
may be linked by comparable ratios or some other normalizing
parameter.

I think the important word here is 'postulate' which of course means
unproven (and maybe unprovable) assertion. Absent proof of a link,
Occam's Razor calls for the least hypothesis - no link.

Industrial safety types love to quote statistics like this to scare
people, but in reality there is usually a reason why some hazardous
encounters lead to accidents or incidents while most do not. It's not
random. These reasons generally have to do with individual skill,
knowledge, and experience as well as factors the industrial safety
people are never told because they involve routine violations of
safety rules. Often the same dynamic plays out in NTSB
investigations.


The intent was not to scare anyone, but to try to add some perspective
tying the comparatively rare accident to the unknown (perhaps
unknowable) number of hazardous situations that are dealt with without
further incident.

And the perspective is flawed.

And yes, there are always reasons why aviation
accidents happen, be it attributable to Software (checklists, SOP's,
etc.), Hardware (airplane, systems, cockpit layout, etc.), Liveware
(the pilot, pax, ATC, etc.), Environment, or the interaction of some
or all of these.

The same is true of industrial accidents. In fact, when you get right
down to it, very few 'accidents' are due to random factors.

In other words, typically 1 out of 331 encounters of a similar type
results in an accident, whether it's precipitated by an engine failure
or an inadvertent stall/spin.

No, this is total nonsense because stall-spins and engine failures are
not similar. First of all, a mechanical failure generally occurs in a
manner that is beyond the pilot's control. When the main seal blows
out, or the engine swallows a valve, or a rod goes through a cylinder,
or the fuel injectors clog with rust - that's almost always completely
independent of pilot skill, knowledge, and judgment. On the other
hand, an inadvertent stall-spin is caused by the pilot. Therefore,
we're not even looking at the same population.

The point of the
pyramidal accident ratio is not to compare engine failures with
stall/spins. Yes, they are two dissimilar accident types in terms of
the driving mechanisms -- the engine in one case vs. the pilot in the
other. But that does not preclude the mix of accidents, hazards, and
incidents within each population from sharing a common relationship.

Well, no - they might share a common relationship through sheer chance
- but that's not the way to bet.

From that standpoint, so what if a hole is blown through the crankcase
and the windscreen gets covered with oil, obscuring the pilot's
ability to see well enough to land under control. The airplane still
gets busted and it's still labelled an engine failure accident.
Likewise, so what if the pilot skids a turn and causes the airplane
to spin into the ground. It's still a stall/spin accident. But for
each one of those accidents, there are many more pilots who, with an
oil-slicked windscreen, were able to land under control; there are
many more pilots who recognized the developing skid, corrected it, and
continued under control. The industrial accident maxim only attempts
to quantify how many within each group were able to avert the
accident.

You can disagree with the theory or its application (in which case, it
would be beneficial to put forth an alternative), but can't you do it
without denigrating?

There's no theory here to disagree with. There is a hypothesis
(advanced without proof) that aviation hazards follow the 1:30:300
distribution, with 331 hazard encounters leading to 30 accidents and 1
fatality (or 30 incidents and 1 accident - depending on how you apply
it). To qualify the hypothesis as a theory, you would need to propose
a logical mechanism for the numerical results. For it to be taken
seriously, you would also need supporting data on the relevant
elements, including some credible data on the rate of hazard
encounters not leading to accidents or incidents. What I am
denigrating here is the attempt to draw conclusions without either.

This is supposed to be a forum for learning -- is
this how you treat your students?

This is certainly how a student in the sciences would expect to be
treated if he tried to pass off the 300:30:1 ratio as a theory.

You're attempting to draw some conclusions about the relative
frequency of stall-spin events relative to engine failure events. No
such conclusions are possible if all you have to look at are accident
statistics.

Just by virtue of the fact that the pilot allowed the inadvertent
stall-spin situation to develop, we can expect that he is less likely
to handle it properly. The same is not true of engine failure.

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.

In the case of NTSB data, one could
extrapolate to get a feel for the order of magnitude of problems
pilots deal with in a particular category by multiplying the number of
accidents by 331.

This is absolutely ridiculous. In addition to the issue of hazard
exposure (mechanical engine failures don't discriminate but
stall-spins do) there is also the issue of hazard magnitude. Off
field landings in gliders, for example, are VERY rarely fatal. The
ratio there is 5000:1. On the other hand, I would be amazed if the
fatality ratio for midairs was much better than 3:1. 331 may be a
good all-around average in aviation (or it may not - data are not
available) but to apply it indiscriminately to all types of hazards
makes no sense at all.

Be gentle, you're dealing with an idiot after all

I doubt it.

Please explain
how an engine failure does not discriminate, yet stall/spin accidents
do. The typical stall/spin profile involves a typical pilot on a
typical flight -- sounds pretty indiscriminate to me.

I don't believe a stall-spin involves a typical pilot at all. I
believe a typical pilot will recognize the loss of airspeed long
before a stall, never mind a spin, actually occurs. The pilot who
allows the situation to deteriorate to the point that an inadvertent
stall occurs is way behind the airplane. Letting it spin is worse.

Of course there are exceptions to this. If you fly just a few knots
over stall in turbulent air long enough (and this is a normal flight
mode for gliders) you will eventually stall. I don't know anyone with
more than 100 hours in a glider who has never stalled in a thermal.
If you fail to control yaw at that point, you will spin, and I know a
few people who have. However, because spin training is still the norm
for glider pilots, and because all glider pilots are aware of the
risk, this situation does not seem to be a significant cause of
fatalities. When glider pilots have fatal stall-spins, they have them
the same way power pilots do - when maneuvering to land.

Please cite your source for the 5000:1 ratio for gliders.

Strictly an estimate based on my experience with the sport. SSA
claims a membership of 14,000. Conservatively speaking, maybe 20% fly
XC, or 2800 people. On average, a XC pilot is going to land out once
a year; more if he's still learning. We have an outlanding-related
fatality once every few years. The last one I recall was Oran Nicks.

Also, glider
pilots are always performing engine-out landings, so it would seem to
make sense that they'd be better at it than those of us who fly
powered airplanes.

Exactly! Further, it's the more skilled glider pilots who go XC and
thus expose themselves to the risk of outlanding. An outlanding in a
glider is an event that discriminates in favor of the more skilled
pilot, and thus I would expect it to have a very low rate of fatality.
On the other hand, a stall-spin discriminates in favor of the less
skilled pilot, and thus I would expect it to have a higher rate of
fatality. Engine failure (due to mechanical problems) does not
discriminate by skill.

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.

As for fatality ratio -- yes, the fatality rates between accident
types is not at all equal.

Well, I'm glad we can agree on that. Now if we can simply get to the
next obvious step, that being that the accident/incident rates between
different types of hazards are not at all equal, and that therefore no
conclusions about the rate of occurence of various hazards can be
drawn from accident/incident reports, we'll have reached agreement.

Michael

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

Kyler

Another true (War) story.

T-28A

7 cyl 900 HP engine. (128+ HP per cyl)
2 blade Aero-Products prop (big wide paddle blades to absorb HP)
Prop shaft cut with a square corner where it transitioned to throw.
At original cruise rpm viborations/stresses caused prop shaft to break
off and prop depart plane.
Result - dead stick with prop missing.

Fixes tried.

1. Tried 3 blade prop which reduced stress on crank - worked but cost
too much to throw away the relatively new 2 blade props and get
new 3 blade props.

2. Dissambled engine and under cut (rounded) square corner betweem
shaft and throw. More failures.

3. Set up a restricted rpm range that could be transitioned but not
fly steady state in.

4. Raised cruise rpm 150 rpm changing stress on crank. These two
worked but reduced range and duraation a lot. Had to refuel after
every training mission vs flying two missions on one load of fuel.

Looks like this true life story supports both sides of the argument?

Big John


On Mon, 01 Dec 2003 20:09:35 GMT, Kyler Laird
wrote:

"Mike Rapoport" writes:

But do you agree that components that require maintenance (propeller,
cylinders, engine mounts, ...) can cause/accelerate crankshaft
failures?

I suppose that I agree to a limited extent, but virtually all
crankshaft/connecting rod failures are caused by a flaw/fault in
design/manufacture or installation. Once the crank or connecting rod is
installed, nothing is done to it and it is unseen until overhaul time. A
failure of either of these components is not going to put much, if any,
metal into the oil until the bitter end either..

I was thinking less of metal in the oil than the forces exerted on the
crankshaft. An out-of-balance prop or even a faulty spark plug can
cause out-of-spec. impluses to be exerted on the crankshaft.

I sure don't know how significant that is likely to be though. ('course
you can consider the stories of pilots taking off after prop. strikes as
an extreme.)

--kyler

(Rich Stowell) wrote
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?

Well, it would be satisfactory if you had a valid way of estimating
the error. However, this still requires data. It's really very
unfortunate that data collection in GA is a bad joke. It's a lot
better at the Part 135/121 levels. For example, in those operations
every engine failure is reported (at least for turbine engines). A
skydiver friend of mine once looked up engine failure rates on the
PT-6 engines that power Twin Otters. The numbers looked artificailly
low to him. He started making phone calls to friends. It's not easy
data to get, but his best estimate is that Twin Otters in Part 91
service have an engine failure rate about 300 times higher than in
Part 91 service. He admits that the real number could be as low as 50
and as high as 1000, because of uncertainties in how operating hours
are estimated as well as uncertainties in which inciddents were
unique.

It's very frustrating as an instructor not to be able to give your
student solid estimates on which risks are truly significant, but the
alternative (reaching firm conclusions from nonexistent numbers) is
far worse.

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

Well, that's great - now define hazardous encounters. With engine
failure, it's easy. The engine stops making power (or stops making
sufficient power to maintain level flight) and you have an encounter.
With off-field landings it's easy - when you commit to an off-field
landing, you have an encounter. Stall-spins are harder. Does the
hazard encounter start when autorotation begins? When the stall
breaks? When the buffet starts? When the stall horn goes off? See
the problem?

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?

Whatever is required to maintain proficiency. If during your
recurrent training cycle you handle the engine failure competently
(meaning accomplish the task smoothly and with the successful outcome
never seriously in doubt) then you are maintaining proficiency.
Otherwise you are not.

Specific numbers are very much a function of the airplane and pilot
proficiency, and one size does not fit all.

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.

I think so too, assuming that what you mean by react appropriately is
point the plane someplace reasonable and maintain proper flying speed
to the flare. I doubt he will select the optimal location or make a
great landing, but those things are probably not crucial to his
survival.

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.

No argument.

In fact, typical pilots under duress will invariably only be able to
perform as well as their most basic skill set allows.

Define most basic skill set. Keep in mind that for some, this will
include night partial panel flying. For others, it may be
substantially more limited.

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.

I'm not convinced that's true. I suspect that the pilots who
voluntarily get emergency maneuvers training are the same pilots who
doubt their ability to handle emergencies. Such doubts are usually
justified.

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.

So how many inadvertent stall-spins do they get to see under normal
conditions?

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.

That's probably true, but on the other hand most modern airplanes have
to be pretty severely mishandled to cause an inadvertent spin. The
same is not true of gliders and aerobatic airplanes, but the people
flying those tend to be trained by a completely different sort of
instructor.

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.

Why do you keep going back to the patently unprovable? All we know is
that they are more likely to have an accident caused by stall-spin
rather than engine failure. This tells us nothing about the
likelihood of encountering either hazard.

Now let's consider something else. A pilot who flies 200 hours a year
is 10 times more likely to have an engine failure than one who flies
20 hours a year, since engine failure is not under his control. Are
you seriously suggesting that a pilot who flies 200 hours a year is 10
times more likely to inadvertently spin than one who flies 20 hours a
year? I would argue that he is LESS likely to inadvertently spin,
since the higher level of proficiency that is a nearly inevitable
result of flying a lot and often will make him less likely to miss the
rather obvious clues.

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).

However, only half of those are private pilots. Tens of thousands are
professional pilots who fly hundreds of hours a year. Thus the
reality is that a large number (maybe the majority) of these 'active'
private pilots are actually flying less than 20 hours a year. IMO it
is not possible for such a pilot to be proficient at all. In fact,
I'm going to take back what I said - if the average pilot is indeed
flying 20 hours a year, then I will readily admit that inadvertent
stall-spin accidents are going to happen to the average pilot. I
guess my point is that they ought not to happen to the proficient
pilot. Instead of looking at total hours, we should really be looking
at hours flown a year, and even then there are other factors since not
all hours are created equal.

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)???

Sure. I guarantee you that there is SOME definiton of "close enough
to each other to be considered a hazardous encounter" that will make
the numbers work. By the same token, there is SOME definiton of
"stall-spin hazard" that will make the numbers work. This is
meaningless.

Michael

(Michael) wrote in message . com...

It's very frustrating as an instructor not to be able to give your
student solid estimates on which risks are truly significant, but the
alternative (reaching firm conclusions from nonexistent numbers) is
far worse.

I agree about the frustration. I disagree that I was in any way trying
to reach firm conclusions; just trying to offer some sense of the
scope of the potential problem, be it engine failures or stall/spins.

And I do think it is fair in the case of the stall/spin, for example,
to say that the last maneuver performed by nearly one out of four
pilots who's aviation career has ended in death and who also ended up
in the NTSB database was a stall/spin. This does provide some context
about the stall/spin risk, especially in the accident process leading
to generation of an NTSB report.


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?

Whatever is required to maintain proficiency. If during your
recurrent training cycle you handle the engine failure competently
(meaning accomplish the task smoothly and with the successful outcome
never seriously in doubt) then you are maintaining proficiency.
Otherwise you are not.


But what about in between the recurrent training cycle? Do you make
any recommendations to your students at all in this regard? What to
work on, how to work on it, what frequency to practice? And in terms
of "smoothly with the successful outcome never seriously in doubt" --
do you apply Practical Test Standards to the tasks -- which are
minimum acceptable standards, i.e.: training to the lowest common
denominator -- or do you challenge your students to be better than the
average, the minimum standard? And if you challenge them to take their
flying to the next level, I would assume that would be based on your
own experience, both personally and as an instructor dealing with the
problems, errors, and misunderstandings your students commonly have
when they fly with you, no?

And I would bet that sans any hard scientific data to support your
anecdotal experience, you could tell me with reasonable certainty
where the problem areas will be, specifically what the errors will be,
etc. that you will encounter with the majority of your students under
certain tasks.


Specific numbers are very much a function of the airplane and pilot
proficiency, and one size does not fit all.

For the majority of GA pilots flying GA airplanes, I have not found
that to be the case at all. The problems I deal with with my students
all fall within a pretty well-defined envelope across the board,
across light, single-engine, GA airplanes. In fact, I would say I've
found it much more difficult for higher time pilots to break their bad
habits simply because the habits have been ingrained for far too long.
The typical profile of the pilot I fly with is a pilot who is active
in general aviation, active in the ratings process, active in the
pursuit of knowledge, experience, safety, and who has 100 to 600 hours
total time. These pilots come from all over the U.S., from all kinds
of flight schools, flying all kinds of light, single-engine airplanes.
And I often fly with them in the equipment they are used to flying.
Anything from the Cirrus SR20/22, to the J-3 Cub, to the C-206 Amphib,
to the Pitts, Pipers, Cessnas, RV's, Zlins, even rarer airplanes like
the Aero Subaru and the FAA Bravo.

In that sense, the pilots I deal with are likely above the average in
terms of their approach to flying and flight safety -- that's why they
are training with me. That and the realization that the primary flight
training process often leaves a lot to be desired in terms of dealing
with many different safety issues, not to mention the pure art of
flying the airplane.



In fact, typical pilots under duress will invariably only be able to
perform as well as their most basic skill set allows.

Define most basic skill set. Keep in mind that for some, this will
include night partial panel flying. For others, it may be
substantially more limited.

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.

I'm not convinced that's true. I suspect that the pilots who
voluntarily get emergency maneuvers training are the same pilots who
doubt their ability to handle emergencies. Such doubts are usually
justified.

See above about the typical pilot profile of those I fly with -- they
are likely above average and at least recognize and deal with any
issues they may have. But for each one of the pilots who takes spin,
EMT, or aerobatic training for safety reasons, there may be scores of
others who have no clue, or who have simply given up and left aviation
altogether because of unaddresses issues/fears that could have been
dealt with.


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.

So how many inadvertent stall-spins do they get to see under normal
conditions?

I'm not sure I understand the question...


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.

That's probably true, but on the other hand most modern airplanes have
to be pretty severely mishandled to cause an inadvertent spin.


Not true -- I routinely demonstrate one variant of the classic skidded
turn base-to-final at altitude with students, and in every single
spins-approved airplane I've ever tried this in, I've been successful
entering a spin from a left turn, with 1200-1800 rpm, without any
aileron, with less than full rudder and elevator inputs, and with the
ball less than 1/2 ball width out of center. This has been true even
in spins-approved airplanes that either would not, or were very
reluctant to, perform a left spin entered normally.

See also "Rudder and Elevator Effects on the Incipient Spin
Characteristics of a Typical General Aviation Training Aircraft." AIAA
Paper 93-0016. Reno, NV: January, 1993, by Patrick Veillette.



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.

Why do you keep going back to the patently unprovable? All we know is
that they are more likely to have an accident caused by stall-spin
rather than engine failure. This tells us nothing about the
likelihood of encountering either hazard.

Thos enumbers are from an NTSB study. I'm notmaking them up. Perhaps
you'd be happier if I prefaced with "Pilots who make it into the NTSB
database share these characteristics..."


Now let's consider something else. A pilot who flies 200 hours a year
is 10 times more likely to have an engine failure than one who flies
20 hours a year, since engine failure is not under his control. Are
you seriously suggesting that a pilot who flies 200 hours a year is 10
times more likely to inadvertently spin than one who flies 20 hours a
year? I would argue that he is LESS likely to inadvertently spin,
since the higher level of proficiency that is a nearly inevitable
result of flying a lot and often will make him less likely to miss the
rather obvious clues.


You admitted yourself, all flight time is not equal. In that regard, I
would say the pilot who flies 200 hours a year of white-knuckled
X-country, averaging one power-on landing every 2 hours, who is
deathly afraid of stalls to begin with and has never spun, and flies
by the adage "maintain lots of extra flying speed just in case" is far
more likely to encounter an inadvertent stall/spin in a stall/spin
critical situation than a pilot who flies 20 hours a year in his
Pitts, 30 minutes at a shot, performing advanced aerobatic maneuvers
and averaging 4 gliding landings per hour (my former Pitts partner did
just this last year). I'd bet on the survival of this Pitts pilot over
the other one in a similar stall/spin critical scenario.

Perhaps a better gage of a pilot's ability to deal with stall/spin
critical operations is not flight time, but rather the number of
landings per hour. After all, one trip around the pattern exercises
many, many critical piloting skills. It would be interesting perhaps
to do a study with this as the hypothesis -- would this interest
you???

Rich
http://www.richstowell.com

(Rich Stowell) wrote
And I do think it is fair in the case of the stall/spin, for example,
to say that the last maneuver performed by nearly one out of four
pilots who's aviation career has ended in death and who also ended up
in the NTSB database was a stall/spin. This does provide some context
about the stall/spin risk, especially in the accident process leading
to generation of an NTSB report.

Yes, this provides some context. Where I disagree is that it provides
any information as to the relative occurrences of stall/spins vs.
engine failures.

But what about in between the recurrent training cycle? Do you make
any recommendations to your students at all in this regard?

Yes - but they are specific to the individual. It can't be otherwise.
I've done recurrent training for a variety of people ranging from low
time private pilots on end of the scale to an airline captain with 5
digit time on the other.

What to
work on, how to work on it, what frequency to practice? And in terms
of "smoothly with the successful outcome never seriously in doubt" --
do you apply Practical Test Standards to the tasks -- which are
minimum acceptable standards, i.e.: training to the lowest common
denominator -- or do you challenge your students to be better than the
average, the minimum standard?

I apply the minimum standard to decide if the person gets a signature
in his logbook certifying that he has completed a BFR/ICC. Beyond
that, I tailor the training to the individual. The guy with less than
10 hours IMC time is challenged when I give him the hardest task of
the flight - I fail his vacuum gyros and autopilot and he has to hand
fly the GPS approach. The airline captain gets to do a single engine
hand flown ILS to CAT II minima as a warmup. The idea that one size
fits all is ridiculous.

Specific numbers are very much a function of the airplane and pilot
proficiency, and one size does not fit all.

For the majority of GA pilots flying GA airplanes, I have not found
that to be the case at all. The problems I deal with with my students
all fall within a pretty well-defined envelope across the board,
across light, single-engine, GA airplanes. In fact, I would say I've
found it much more difficult for higher time pilots to break their bad
habits simply because the habits have been ingrained for far too long.
The typical profile of the pilot I fly with is a pilot who is active
in general aviation, active in the ratings process, active in the
pursuit of knowledge, experience, safety, and who has 100 to 600 hours
total time.

In other words, you're mostly flying with low time pilots. I suppose
the lower the experience level, the more consistent the performance.
After all, at zero hours most people perform about the same

Seriously, because of the kind of instruction you do, your clientele
is self-selected. I think that tends to homogenize the sample.

In that sense, the pilots I deal with are likely above the average in
terms of their approach to flying and flight safety -- that's why they
are training with me.

One could just as easily say that they lack confidence and feel the
need for additional training in emergency procedures, and maybe the
lack of confidence is justified.

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.

So how many inadvertent stall-spins do they get to see under normal
conditions?

I'm not sure I understand the question...

When doing aerobatic (or emergency maneuvering) training, the
probability of inadvertent stall is high. In fact, I have
inadvertently stalled several times, and once almost spun, but every
one of those instances was while learning or practicing aerobatic
maneuvers. These are not normal conditions, and in any case the risk
is low because everything is done at relatively high altitude, in an
appropriate airplane, with proper training, etc.

I've also seen one inadvertent stall-spin from the back seat of a
glider. The student was a very low time power pilot on his first
glider flight, and he was practicing thermaling flight. That's what I
mean by normal conditions - when a student is doing routine things and
botches them badly enough to stall and spin.

Not true -- I routinely demonstrate one variant of the classic skidded
turn base-to-final

I think skidding the base to final turn AND being slow is pretty
serious mishandling of the airplane. In a glider instructional
situation, it's certain to cause noise from the back seat. Of course
the profile of the average glider instructor is a lot different from
the average power instructor.

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.

Why do you keep going back to the patently unprovable? All we know is
that they are more likely to have an accident caused by stall-spin
rather than engine failure. This tells us nothing about the
likelihood of encountering either hazard.

Thos enumbers are from an NTSB study. I'm notmaking them up. Perhaps
you'd be happier if I prefaced with "Pilots who make it into the NTSB
database share these characteristics..."

No, the proper preface is "Accidents that make it into the NTSB
database share these characteristics." You have absolutely no idea
what sort of hazard encounters these pilots had that did not end in an
accident. The concept I'm going for here is "The rate of accidents is
not an indicator of the rate of hazard encounters."

Now let's consider something else. A pilot who flies 200 hours a year
is 10 times more likely to have an engine failure than one who flies
20 hours a year, since engine failure is not under his control. Are
you seriously suggesting that a pilot who flies 200 hours a year is 10
times more likely to inadvertently spin than one who flies 20 hours a
year? I would argue that he is LESS likely to inadvertently spin,
since the higher level of proficiency that is a nearly inevitable
result of flying a lot and often will make him less likely to miss the
rather obvious clues.

You admitted yourself, all flight time is not equal.

Absolutely. It's simply the only reliable measure we have.

In that regard, I
would say the pilot who flies 200 hours a year of white-knuckled
X-country, averaging one power-on landing every 2 hours, who is
deathly afraid of stalls to begin with and has never spun, and flies
by the adage "maintain lots of extra flying speed just in case" is far
more likely to encounter an inadvertent stall/spin in a stall/spin
critical situation than a pilot who flies 20 hours a year in his
Pitts, 30 minutes at a shot, performing advanced aerobatic maneuvers
and averaging 4 gliding landings per hour (my former Pitts partner did
just this last year). I'd bet on the survival of this Pitts pilot over
the other one in a similar stall/spin critical scenario.

No argument at all. And unfortunately I've met the 200 hours of white
knuckled XC guy. He absolutely refured to turn off the autopilot in
IMC; I could tell he was extremely nervous when I hand flew his plane
for a few minutes. His landings are all power-on. If he encounters a
spin, I doubt he will survive it. But he's not the norm, either.
Typically when a pilot flies 200 hours a year, he's proficient.

Perhaps a better gage of a pilot's ability to deal with stall/spin
critical operations is not flight time, but rather the number of
landings per hour.

I would say landings per year, and rate power-on and power-off
differently. For that matter, different aircraft rate differently.
In a glider, you're never far from a stall. In fact, I have to wonder
if my experience with students is skewed because so many of them are
glider pilots as well... In a Cherokee, you have to work hard to
stall.

After all, one trip around the pattern exercises
many, many critical piloting skills. It would be interesting perhaps
to do a study with this as the hypothesis -- would this interest
you???

Sure. Where would you get the data?

Michael