AOPA Stall/Spin Study -- Stowell's Review (8,000 words)

Since the airspeed indicator (pitot tube) is pointed the same as the
wing, then "indicated airspeed" does mean something. For instance, if you
were to put the wing at a 90 degree AOA to the relative wind, then the
airspeed would also read nothing or almost nothing correct?

So I agree that airspeed doesn't matter, but indicated airspeed does.

Wayne



Remove "bra" and "panties" to reply

Airspeed alone means nothing with regard to when or whether the
airplane will stall. We need to think in terms of airspeed AND G-load
-- these are the two parameters that will give us a clue as to our
margin to the stall, or whether or not we are moving closer to, or
farther from, critical angle of attack

"Wayne" writes:

Since the airspeed indicator (pitot tube) is pointed the same as the
wing, then "indicated airspeed" does mean something. For instance,
if you were to put the wing at a 90 degree AOA to the relative wind,
then the airspeed would also read nothing or almost nothing correct?

So I agree that airspeed doesn't matter, but indicated airspeed
does.

His point was that the stall speeds marked on the ASI (Vs and Vso) are
applicable only at 1 G, maximum gross weight, and the appropriate
flap/gear configuration. That's why an angle-of-attack indicator
would be nice.

If you're doing anything that increases the G-load on the plane, like
turning or pulling up from a dive (i.e. anything that presses your
behind into the seat), the stall speeds will be higher; if the plane
is loaded below maximum gross weight, the stall speeds will be lower;
and so on.

It's a bit of an overstatement to say that stall speeds don't matter,
but you do have to take them with a big grain of salt. Let's say that
you have just recovered from a stall or spin and are now in a dive
heading quickly towards the ground. If you pull up hard, you might
stall the plane at close to double the Vs marked on the ASI.


All the best,


David

"David Megginson" wrote in message
...
His point was that the stall speeds marked on the ASI (Vs and Vso) are
applicable only at 1 G, maximum gross weight, and the appropriate
flap/gear configuration. That's why an angle-of-attack indicator
would be nice.


Well, in a way, the airspeed indicator IS an angle-of-attack indicator.

--
Chris Hoffmann
Student Pilot @ UES
30 hours

Airspeed alone means nothing with regard to when or whether the
airplane will stall. We need to think in terms of airspeed AND G-load
-- these are the two parameters that will give us a clue as to our
margin to the stall, or whether or not we are moving closer to, or
farther from, critical angle of attack.

......But won't airspeed alone change the "cushion" that you have to maneuver
with? A steep turn at 90 kts isn't usually a problem. Doing something like
that near Vso on final will almost certainly be one. As you point out, at
lower airspeeds the aircraft will stall with less of a load.

I don't dispute that there's more to stalls than airspeed. I just think
you're all putting too fine a point on this. If the hypothetical instructor
said, "Watch your airspeed, or you'll reduce the amount of G-load that the
airplane can handle and may invoke a stall if you decide to maneuver
drastically", then you probably wouldn't have a problem with it, but in the
time it took to say all that, the instructor and student would be hitting
the ground! Proper instruction of what causes a stall is one thing. Not
letting your student get out of control on an approach is another.

Let's "approach" this another way: You're the instructor in this case. Do
you want your student to maintain a certain airspeed on approach? If so,
why? And if they allow the plane to get below that speed, what are you going
to say to them?

--
Chris Hoffmann
Student Pilot @ UES
30 hours

I don't dispute that there's more to stalls than airspeed. I just
think you're all putting too fine a point on this.

I agree with you.

For every constant g-loading, there is an airspeed which is safe to
fly.

On Mon, 01 Sep 2003 20:18:34 GMT, "Chris Hoffmann"
wrote:

Airspeed alone means nothing with regard to when or whether the
airplane will stall. We need to think in terms of airspeed AND G-load
-- these are the two parameters that will give us a clue as to our
margin to the stall, or whether or not we are moving closer to, or
farther from, critical angle of attack.

.....But won't airspeed alone change the "cushion" that you have to maneuver
with? A steep turn at 90 kts isn't usually a problem. Doing something like
that near Vso on final will almost certainly be one. As you point out, at
lower airspeeds the aircraft will stall with less of a load.

I don't dispute that there's more to stalls than airspeed. I just think
you're all putting too fine a point on this. If the hypothetical instructor
said, "Watch your airspeed, or you'll reduce the amount of G-load that the
airplane can handle and may invoke a stall if you decide to maneuver
drastically", then you probably wouldn't have a problem with it, but in the
time it took to say all that, the instructor and student would be hitting
the ground! Proper instruction of what causes a stall is one thing. Not
letting your student get out of control on an approach is another.

Let's "approach" this another way: You're the instructor in this case. Do
you want your student to maintain a certain airspeed on approach? If so,
why? And if they allow the plane to get below that speed, what are you going
to say to them?

If the instructor only says to the student "Ensure your airspeed on
approach is above the stall speed", then the instructor is not
fulfilling his/her responsibility to the student.

If the instructor says to the student "Since we are flying at just
about a constant 1G throughout the approach, the Vso stall speed
marked on the airspeed indicator is the speed at which the aircraft
will stall. Therefore, keep a margin of whatever the instructor
determines is appropriate knots above that Vso airspeed as some
protection against a stall." then the instructor is working a a
proper foundation of understanding for the student.

By the way, "Stick and Rudder" is probably my favorate book on
flying too, but it must be read carefully and critically.

Originally Posted by Chris Hoffmann

The first thing that jumped out at me from your report is this:

Another myth cited in the AOPA study is "watch your airspeed, or
you're going to stall this airplane!"

Pardon me, but if your airspeed gets below stall speed, you ARE going to
stall. Further, if your airspeed is below the usual 1.3 Vso safety cushion,
you are getting to the point where all it takes is a turn too steep, or a
bit of tailwind, or a yank back on the yoke, and you are LIKELY to stall.
This is not "myth".
snip

I was fortunate enough to have taken Rich's EMT training twice many years ago. "Stall speed" as noted in the POH for your airplane really means "stalling speed at 1G". The wing can stall, or not stall, at any speed down to zero - it depends on the AOA and nothing more. Think about a hammerhead turn: you go vertical, and at the top the wing has a nearly zero speed, but also a nearly zero AOA, so it doesn't "stall" and then nose over to the front.

In the interest of fairness, following is the AOPA ASF response to my
review. All of this, including the link to the original study, is
posted on my web site as well at http://www.richstowell.com/aopa.htm:


-------START-------

September 8, 2003

Dear Rich:

Thanks for your review of ASF's report on the role of stall/spin
accidents in general aviation. Having an extra voice on the subject -
especially from a respected unusual attitude trainer like yourself -
can only help in our common mission of educating pilots and improving
the GA accident rate.
Reading through your comments, it sounded a bit adversarial in places
and yet we agree on many points. In the very first paragraph, you
accuse ASF of fabricating a myth [ Pilots who believe that aerobatic
training will enable a recovery from an inadvertent spin in the
traffic pattern are fooling themselves. ] solely for this study. To
provide a more balanced viewpoint, you might also have quoted the next
few sentences "This study is not intended to discount the value of
properly conducted aerobatic and spin training. Training in a
controlled environment with a trained instructor is beneficial. The
most important aspect of the training should be recognition and
prevention."

That doesn't sound like we "….essentially missed the point of spin
training."

Regarding the myth, I'd suggest that the reason you hadn't heard it
is that it exists mostly among the pilots you HAVEN'T been associating
with - those who haven't sought out spin training, and who aren't
professional spin or aerobatic instructors. The pilots who subscribe
to this myth are among many all over this country who pick up much
incorrect information in the process of hangar flying. They may be a
minority, but minorities are precisely the ones who make the accident
statistics, but let's get to some of your key points.

"The study claims that this myth ("watch your airspeed, or you're
going to stall this airplane") is largely propagated by flight
instructors...."

We agree that it IS largely propagated by flight instructors. It was
nice of you to add that many of those instructors are low-time,
under-trained and/or under-informed, but that's something we've agreed
upon in the past and continue to do so. We also clearly laid out the
true path to safety lies in the angle of attack.

"AOPA has been known to disseminate stall/spin mythology as well."

We did explore the possibility of proving (or disproving) the
statement that more pilots were killed in spin training accidents than
in real emergencies. That information was provided by several FAA
officials, who believed that to be the case. We couldn't prove that,
either way, if the "more" was correct. There were certainly training
accidents, however. Older NTSB records were only recently made
available online, and even then only back to 1962. Again, you left
out context by not quoting the sentence preceding, " Because of
improved aerodynamics and an emphasis on avoidance, the number of
spin-related accidents has dropped significantly."

"I believe... however, that... in exchange for relaxing spin training
and aircraft spin certification requirements, manufacturers were to
develop more spin resistant designs. Manufacturers have largely failed
to live up to their end of the bargain."
We agree again and it's right there in the ASF study: "Officials at
the time also reasoned that if there was no spin requirement for
private pilots, then aircraft manufacturers would also be encouraged
to produce aircraft with greater spin-resistant characteristics." In
addition, ASF's new premier live seminar on Maneuvering Flight (which
will debut at AOPA Expo in October and will run through the first half
of 2004 nationwide) uses a NASA study and other evidence to clearly
establish that not everything possible has been done through aircraft
engineering to minimize stall/spin accidents.
There is some movement in that direction recently with the
certification of spin resistant aircraft and your own point, that one
reason for the drop in accidents was that newer aircraft introduced in
the 50's and beyond were somewhat more spin resistant. So technology
does make a difference, perhaps more reliably than other methods. By
the way, in the seminar we recommend that if pilots elect to take
unusual attitude and spin training, that they go to professionals like
you who have the expertise and the equipment to do the job safely.

"Of interest is AOPA's conclusion that "it appears that ATP's are
generally the most experienced and knowledgeable pilots, while
students are under very close supervision to ensure their safety."

The additional study of ATP stall/spin accident rates in your report
certainly is interesting, but it only confirms ASF's original
conclusion that private and commercial pilots were the groups most in
danger of a stall/spin accident. We did NOT look at aerobatic
involvement.
"If the reason Student pilots have a 4 percent stall/spin fatality
rate is due to "very close supervision to ensure their safety" as
concluded in the AOPA study, then wouldn't it follow that flight
instructors would also have a comparably low stall/spin fatality
rate?"

Students, by regulation, are required to have very close supervision
in all phases of training leading up to the private pilot certificate.
Regarding CFI's being as safe, No, not necessarily. It is the CFI's
doing the supervising for solo students and they appear to apply
different standards to themselves when in a dual flight situation.
As the ASF study points out, the numbers involved are fairly small: a
total of only 44 fatal stall/spin accidents in an instructional
setting over a 10-year period. That the majority (91%) happened with
CFIs on board may very well be due to insufficient spin training of
CFIs today, as those CFIs provide dual instruction in some of the most
risk-prone corners of the flight envelope.
"(The decrease in stall/spin accidents after 1949) myth attempts to
create a non-existent cause-and-effect relationship."
Not quite sure what you're saying here, but there is no myth that spin
accidents when down, coincident with the deletion of the spin demo
requirement. We absolutely agree this was also influenced by multiple
factors previously mentioned.
Aviation accident investigation and reporting not only isn't an exact
science, but (as we all agree) has changed and evolved over the years.
Your report on the ASF study points out quite correctly that many
factors could be involved in the decrease in the number of stall/spin
accidents since deletion of the spin requirement from the private
pilot certificate in 1949, including changes in training and testing,
training methodologies, aircraft engineering and other things. Even
definitions of accident causes have evolved over the years, further
muddying the water. But on its most essential level, NTSB accident
reports clearly show that GA accidents due to stalls and spins have
indisputably decreased over the years.

"The discussion of altitude losses during stalls and spins referenced
in the AOPA study lacks context; the information as provided,
therefore, is misleading."

No, all the context is there, including the sources for data ASF used
in the study. In the case of average altitude loss during stalls, we
used the best available information from the manufacturers. Most
pilots understand that professional test pilots using new aircraft
conduct these tests, and that the individual pilot's mileage may vary,
usually in the direction of more, rather than less, altitude loss. Is
there a CFI anywhere who has not warned students, "give yourself some
margin when calculating aircraft performance?"
For other aspects of altitude losses, we used the best available data
from extensive FAA and NASA tests, as well as an in-depth study of our
own GA Accident Database. Bottom line - the numbers in the POH are
the basis upon additional decisions should be made. You have to start
somewhere and this conversation proves our point - recovery from a low
altitude spin is unlikely.

"Here, too, the AOPA study misleads readers regarding so-called
significant differences between Tomahawk and Cessna 150/152 spin
behavior."

We've been down this road before, and our conclusion that the Piper
Tomahawk is NOT a particularly dangerous airplane when properly flown
stands. It does have spin behavior that - while meeting FAA
certification standards - is not as docile as most, other training
aircraft, but that in itself doesn't make it dangerous. As with many
aviation safety issues, it's the pilot who makes the difference,
especially when dealing with matters of aircraft design.
Since our last go-around on this issue, we've been watching the
accident record for Piper Tomahawks very carefully to see if your
concerns about the design could be validated. So far, they can't: the
last stall/spin accident involving a Tomahawk was in 1999, near
Warrensburg, Illinois. The aircraft had been loaded nearly 100 pounds
over its maximum gross weight, which the NTSB cited as a contributing
factor. If there was a systemic problem I believe we'd see more than
one accident in 4 years. Will there be another PA38 spin accident in
the future? Probably, which will raise all the old arguments but
pilots do have to understand the nature of their machines. Occasional
individual failures, as tragic as they may be, do not show
non-compliance with certification rules. It shows that some aircraft
are not as docile as others in certain flight regimes. Your original
position, as I recall was that the Tomahawk was a dangerous aircraft.
ASF's consistent position is that this aircraft, like many, that has
some different traits that pilots should be aware of.
We'd also direct your readers to my feature article that appeared in
February '03 AOPA Pilot - Spinning In -
http://www.aopa.org/asf/asfarticles/2003/sp0302.html. It reviews some
of this history, interesting NASA research and of the challenges of
educating pilots in spin resistant aircraft. Like any airplane, they
shouldn't be flown contrary to explicit warnings in the POH.
Rich, I'd like to thank you for your analysis of the ASF study,
because it provides solid additional information that - for the most
part - reinforces the conclusions in the ASF study. There are some
points that were taken out of context, but generally, we agree. I also
remind your readers that we are proponents of quality unusual attitude
training as stated in the opening paragraph of the study.

Safe Flights,

Bruce Landsberg
Executive Director
AOPA Air Safety Foundation

-------END---------

"Rich Stowell" wrote in message
om...
In the interest of fairness, following is the AOPA ASF response to my
review. All of this, including the link to the original study, is
posted on my web site as well at http://www.richstowell.com/aopa.htm:


Dead link

Morgans wrote:
"Rich Stowell" wrote in message
om...

In the interest of fairness, following is the AOPA ASF response to my
review. All of this, including the link to the original study, is
posted on my web site as well at http://www.richstowell.com/aopa.htm:



Dead link


Live link
http://www.richstowell.com/aopa.htm


WW