(Michael) wrote in message . com...
(Rich Stowell) wrote
Sorry I can't point you to the "harder" data you're looking for, but
here's perhaps a little perspective on the issue:

According to one NTSB Study, 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 (i.e.: a
random-event engine failure, not one attributed to such pilot errors
as fuel mismanagement).

Really? If that were true, then there would be hard data.


Yes, really -- see "A Study of Light Plane Stall Avoidance and
Suppression." By D.R. Ellis, Report No. FAA-RD-77-25, 1977, p. 6. As
for the "hard data" behind this finding, that's for you to follow up
on since this is your research project


What the NTSB study REALLY says is that these low time pilots are more
likely to encounter an inadvertent stall/spin LEADING TO AN ACCIDENT
than to have a genuine engine failure LEADING TO AN ACCIDENT.


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.


This is
because an engine failure rarely leads to an accident (at least if the
ones known to me are any indication) but an inadvertent stall/spin
usually leads to an accident.


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."

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. 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.

While it is true that one accident classification may be more
prevalent than another (e.g.: more stall/spin fatalities than ground
loop fatalities), the ratio of accidents-to-total encounters may very
well be equal. In that case, 1 out of 331 would be the same for engine
failures leading to accidents as for stall/spins leading to accidents,
or any other accident type. I guess one could argue that 1 accident
out of every 331 hazardous encounters is "rare" regardless of the
cause. In that context, one could then argue that compared to the
total number of stall/spin encounters, stall/spin accidents are
equally as "rare" as engine failure accidents.


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." See "General Aviation Pilot Stall
Awareness Training Study," by William C. Hoffman and Walter M.
Hollister, Report No. FAA-RD-77-26, 1976, p. 6.

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.

For example, stall while at 1-g and Vso and give it some yaw = spin;
stall at 1.95 times Vso with +3.8-g's (that's the same as saying "Va
and the design limit in the Normal Category") and give it some yaw =
spin; give any airplane the right amount of g's at a given airspeed
and give it some yaw = spin.

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.

Rich
http://www.richstowell.com