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

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".

On the other hand, this:

"Just don't let airspeed get below a safe value and
stalls are not a problem."

is not an axiom to fly by. Students *should* know/be taught that a stall can
occur at any speed, any attitude, of course. But I see nothing wrong with
training students to keep their airspeed where it's supposed to be in the
pattern and on approach, which, I believe, is the context from which those
two quoted remarks were taken.

--
Chris Hoffmann
Student Pilot @ UES
30 hours

Chris,

It IS a myth. Stall is related to critical angle of attack and has
absolutely nothing to do with airspeed. The quoted stall speeds are based
on very important assumptions of configuration and power setting. Typically
when people talk about the stall speed of an airplane, they mean V0, which
is clean, flaps up, power off.

You can stall the airplane at Vne if you pull hard enough. There are enough
warbird accidents where the pilot stalled at the bottom of the loop and
flopped flat into the ground to prove the theory.

Shawn
"Chris Hoffmann" wrote in message
...
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".

On the other hand, this:

"Just don't let airspeed get below a safe value and
stalls are not a problem."

is not an axiom to fly by. Students *should* know/be taught that a stall
can
occur at any speed, any attitude, of course. But I see nothing wrong with
training students to keep their airspeed where it's supposed to be in the
pattern and on approach, which, I believe, is the context from which those
two quoted remarks were taken.

--
Chris Hoffmann
Student Pilot @ UES
30 hours

What's more, it is possible, though difficult, to fly slower than Vs and NOT
stall. Trivially, when the plane is standing on the ground, it is not
stalled.
If you botch a loop you can easily end up inverted at the top of a loop
with almost zero airspeed, and not be stalled. Of course in normal
flight it's very hard to lose speed without stalling, but if you
pull vertical you can do it. It's true that if you're below Vs and
not stalled, you won't have much lift either and you'll be
falling. But the airflow is still attached to the wing, and hence you are
not stalled.

John

"ShawnD2112" wrote in message
...
Chris,

It IS a myth. Stall is related to critical angle of attack and has
absolutely nothing to do with airspeed. The quoted stall speeds are based
on very important assumptions of configuration and power setting.
Typically
when people talk about the stall speed of an airplane, they mean V0, which
is clean, flaps up, power off.

You can stall the airplane at Vne if you pull hard enough. There are
enough
warbird accidents where the pilot stalled at the bottom of the loop and
flopped flat into the ground to prove the theory.

Shawn
"Chris Hoffmann" wrote in message
...
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".

On the other hand, this:

"Just don't let airspeed get below a safe value and
stalls are not a problem."

is not an axiom to fly by. Students *should* know/be taught that a stall
can
occur at any speed, any attitude, of course. But I see nothing wrong
with
training students to keep their airspeed where it's supposed to be in
the
pattern and on approach, which, I believe, is the context from which
those
two quoted remarks were taken.

--
Chris Hoffmann
Student Pilot @ UES
30 hours

John - Just to be clear, I'm only referring to approaches. I thought that's
what that part of the original post was about - a student learning to land.

Sean-
How can you say that stalls are unrelated to airspeed, when airspeed is
related to your angle of attack? (and John, at the top of a loop at zero
airspeed, where is the relative wind coming from, or at least about to come
from? Good thing a cliff doesn't magically appear under you at that point.)

You aren't (hopefully) coming in to land at Vne. Yes, you can stall an
airplane at any speed, but the point is you don't want to let your airspeed
drop too low on approach. Period.

Maybe I'm seeing this as two seperate training issues, whereas others are
seeing it as one and the same?

--
Chris Hoffmann
Student Pilot @ UES
30 hours

"Chris Hoffmann" wrote in message ...
John - Just to be clear, I'm only referring to approaches. I thought that's
what that part of the original post was about - a student learning to land.

Sean-
How can you say that stalls are unrelated to airspeed, when airspeed is
related to your angle of attack? (and John, at the top of a loop at zero
airspeed, where is the relative wind coming from, or at least about to come
from? Good thing a cliff doesn't magically appear under you at that point.)

You aren't (hopefully) coming in to land at Vne. Yes, you can stall an
airplane at any speed, but the point is you don't want to let your airspeed
drop too low on approach. Period.

Maybe I'm seeing this as two seperate training issues, whereas others are
seeing it as one and the same?

Chris, you have a good point. Yes, the stall speed of your plane
changes with a variety of factors but we're talking about a known
situation, landing. Not a 3 G turn or floating a loop over the top at
..5 Gs. While a J-3 cub is easily landed without reference to airspeed,
as you go up in aircraft watching *SPEED* on final becomes more
important, unless you are likey enough to own an AOA gauge. In fact,
in heavy iron flying this *SPEED* is computed for that exact flight,
so each approach may have a different approach speed. For a 172,
things like weight variations aren't as critical as in a 747 so we
provide students with a target number for appoach. Of course, if you
choose to pull a 3 G turn or over gross the plane, that number will
not work. I think people are just poking you here to see how you will
react. As a Mooney owner I can tell you speed is critical. The Mooney
Aircraft & Pilots Association recommends no more than 1.2 Vso for
normal landing since being 10 knots fast sucks up about 1500 feet
extra runway. Yes, weight or G loading will effect this (density
altitude and humidity will effect the TAS of the stall too, but we're
just interested in IAS here). Bush pilots often stall there planes
before coming down to know what indicated *SPEED* their plane will
stall at with the current weight. This allows them to land very, very
short.

-Robert, CFI

"ShawnD2112" wrote in message

You can stall the airplane at Vne if you pull hard enough. There are
enough
warbird accidents where the pilot stalled at the bottom of the loop and
flopped flat into the ground to prove the theory.

But not likely at Vne. That is likely to massively overstress the airframe.
moo

Chris Hoffmann wrote:
On the other hand, this:
"Just don't let airspeed get below a safe value and stalls are not a problem."
is not an axiom to fly by. Students *should* know/be taught that a stall can
occur at any speed, any attitude, of course. But I see nothing wrong with
training students to keep their airspeed where it's supposed to be in the
pattern and on approach, which, I believe, is the context from which those
two quoted remarks were taken.

And do not forget that stall speed increases with angle of bank and
G-loading.
Look at the POH for the aircraft you fly and find the charts that list
the stall speed at various angles of bank and flaps.
Remember that the listed stalls speeds are for max gross weight, unless
your POH specifically list stall at other weights. Reduce the aircraft
weight and the stall speeds reduce linearly.
If you increase the G-load (positive) you generally increase the stall
speed. Similarly, if you decrease G-load (negative or less than one) you
reduce stall speed.

"Chris Hoffmann" wrote in message ...
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".


Ah, but therein lies the rub! Within the ability of the structure to
withstand G-load without deforming/breaking, the airplane can be
stalled at ANY airspeed. In that context, every airspeed is a
potential "stall speed" provided the G's applied are sufficient to
exceed critical angle of attack. "Getting below stall speed" is only
meaningful if the instantaneous G-load is specified.

For example, if I pull 3.8 G's while at Maneuvering speed, Va, the
airlane will stall (Va = 1.95Vso). If I am in wings-level flight (1
G), then the stall speed is Vso. An infinite number of G and speed
combinations exists in between Va and Vso that will result in a stall,
even 1.3Vso is a stall speed at the appropriate G-load (G can also be
interpreted as bank angle).

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.

To reduce the likelihood of stalling: If airspeed is decreasing,
G-load MUST also decrease; if airspeed is increasing, then the
airplane can tolerate an increase in G's. We need to develop a sense
of changes in both speed and G to have any reasonable chance of
sensing our proximity to stall.

Also, even the AOPA study correctly identifies the "watch your
airspeed" statement as a myth. I was just expanding on it...



On the other hand, this:

"Just don't let airspeed get below a safe value and
stalls are not a problem."

is not an axiom to fly by. Students *should* know/be taught that a stall can
occur at any speed, any attitude, of course. But I see nothing wrong with
training students to keep their airspeed where it's supposed to be in the
pattern and on approach, which, I believe, is the context from which those
two quoted remarks were taken.

Sensing airspeed AND G-load trends are critical, not airspeed alone.
The V-G diagram is the best illustration of the interaction of speed,
G, stall, and structural damage.

Be Safe,

Rich
http://www.richstowell.com

(Rich Stowell) writes:

For example, if I pull 3.8 G's while at Maneuvering speed, Va, the
airlane will stall (Va = 1.95Vso). If I am in wings-level flight (1
G), then the stall speed is Vso. An infinite number of G and speed
combinations exists in between Va and Vso that will result in a stall,
even 1.3Vso is a stall speed at the appropriate G-load (G can also be
interpreted as bank angle).

Don't forget to add in the case of pulling out of a dive.


All the best,


David

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