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


(Michael) wrote in message . com...
(Rich Stowell) wrote
Really? If that were true, then there would be hard data.
Yes, really

No, not really. No hard numbers on actual engine failures (or
stall-spins for that matter) - only the ones that led to an NTSB
reported accident.


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? Have you followed up on the
references cited in that study to see where it might lead in the quest
for hard numbers on this issue? Or is it easier to just tell everyone
else that they're idiots rather than trying to make a serious
contribution to the discussion?


True, but that's stating the obvious since NTSB only gets involved in,
and thus only reports on, those encounters that have led to actual
accidents.

But this hideously skews the picture. The only way the events are
comparable is if the probability of an engine failure leading to an
accident is approximately equivalent to the probability of a
stall-spin leading to an accident. This is exactly what I am
disputing.


If it "hideously skews the picture" wouldn't that apply to all
accident numbers from NTSB? 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. But useful information
can be gleaned. Insight into the broader problems might be found as
well. And yes, some kind of logical extrapolation may then be possible
to assess the overall magnitude of the issue.


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


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 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.


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.

OK, Michael knows best, everyone else is an idiot. 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.

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


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. I would postulate
that the majority of active pilots (except maybe for students)
practice simulated engine outs far less than 50% of the time.


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 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.

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

As for mid-airs, during the period 1977-1986, 40 percent of the
mid-airs ended without injury.

As for fatality ratio -- yes, the fatality rates between accident
types is not at all equal. But for the purposes of counting accidents,
a situation in which the pilot walks away unhurt, but the airplane's
wing is torn off, is still an "accident" and is therefore equivalent
to a case where a pilot lands in a field with the only damage being a
tree branch through the windscreen, which kills the pilot. They are
both accidents per the definition of the term.


For that matter, most engine failure fatalities in light singles are
not the result of collision with terrain (which is usually survivable)
but of failure to maintain flying speed (which usually isn't). That's
basically a stall/spin anyway.

Two things: First, approximately 19 percent of stall/spin accidents
are preceded by an engine failure. But the primary accident cause is
still listed as "stall/spin."

There is one school of thought that considers this proper. Just
because engine power is lost is no excuse to stall and spin. Gliders
don't even have engines. However, that doesn't change the fact that
had the engine kept running, the stall-spin would likely not have
happened.

Second, the contention that "failure to maintain flying speed" is
"basically a stall/spin anyway" is pure myth. Spins are the result of
two ingredients that must coexist: yaw and stall. And neither yaw nor
stall is a function of airspeed. Up to the point where the wings
decide to bend or break, stalls and spins can and do occur at any
airspeed, and in any attitude.

That's all great, but the reality is that in normal flight (not
involving aerobatics or other abrupt maneuvering) stall avoidance is
all about keeping your airspeed up. Those 19% of stall-spins caused
by engine failure are the result of trying to stretch the glide or
maneuvering to make a landing area, and likely both.

In my experience, and based on the research I've read, I'd postulate
that the majority of stall/spin accidents occur with the airplane
operating somewhere between 1.07 to 1.20 times Vso and 1.15 to 1.41-g.
In other words, with pilots pulling into an uncoordinated, accelerated
stall while turning at bank angles between 30 and 45 degrees.

That's great, but had those pilots maintained at least 1.3 Vso for
these maneuvers, they would not have stalled. Thus saying airspeed is
irrelevant is technically correct but not particularly useful.

Yes, you can stall at any airspeed in any attitude. I've stalled at
100+ kts (in a plane which normally stalled at 60 kts), full power,
and the nose 80 degrees below the horizon - as an aerobatic instructor
I'm sure you know exactly what I did wrong to make that happen. That
doesn't change the reality - in an engine-out situation, the
stall-spin is caused by a failure to maintain flying speed.


No -- the stall/spin is caused by yaw and stall, period. Don't yaw and
the airplane will not spin, regardless of speed. Be aware of the
relationship between g-load and airspeed trend and accidental stalls
are less likely. Continuing to tell pilots to fly faster, in order to
"maintain flyng speed," unneccessarily makes a lot of perfectly good
runways either inaccessible or dangerous to too many pilots. I've seen
only two stall/spin accidents here at my 2500-foot home airport over
the years, but I've seen many more airplanes broken because they
over-ran the runway flying fast enough to "maintain flying speed."

As educators, we can do better than that...

Rich
http://www.richstowell.com