Angle of attack

[Bill Daniels]

The threads on this subject has uncovered something that gives me chills.

Internationaly, gliding has an abominable safety record. Many fatal
accidents have as their root cause, failure by the pilot to maintain flying
speed or, stated more directly, control his angle of attack. Clearly, based
on these r.a.s threads on the subject, some do not understand AOA in some
fundamental way and that's chilling.

Controlling airspeed is simply not good enough - it's too abstract, too easy
to triviallize, too easy to misunderstand the significance of it.

Safety committees and organizations need to take this to hart. Here is a
root cause of our most dangerous accidents. The awareness of and
understanding of AOA has somehow slipped through the cracks. Slay this
dragon, and our accident numbers will look far better.

If the concept and practice of controlling angle of attack is not absolutely
ingrained in a pilot, the probability of an accident is non-trivial - in
fact, sooner or later, it's a near certainty. Awareness of AOA should never
be far from a pilots consiousness.

Controlling angle of attack is so fundamental to being a pilot that it's
staggering to think that it's possible to become one without it being
hammered into them until it's as instinctive as walking. Flying an aircraft
without this level of understanding is like being the captain of a ship
without understanding what makes it float.

As pilots, we do not fly the cockpit, the fuselage or the empenage - we fly
the wing. The wing is really the only thing that does fly, the rest is just
baggage.

Read Jim Webb's truly excellent book "Fly the wing".
http://www.amazon.com/Fly-Wing-James-Webb/dp/0813805414

Or equally good, Wolfgang Langewiesche's "Stick and Rudder". You can read
it free on line at Google Books.

Read these books - please! There is simply no subject in aviation that is
more fundamental or important to your survival.

Bill Daniels

[Udo]

I broached a subject on the http://soaringcanada.riq.ca/ The Round
Table but not with a direct question about A of A but more general, to
see what the response was. I tought it was interesting and revealing.
I ask "A question on minimizing stall accidents". I wanted to get a
sense of how this critical phase was being taught, in light of an
accident that happened just prior. If you want to see the answer you
my want to read some of the comments.
Udo




On Dec 11, 9:27 pm, "Bill Daniels" <bildan@comcast-dot-net> wrote:
> The threads on this subject has uncovered something that gives me chills.
>
> Internationaly, gliding has an abominable safety record. Many fatal
> accidents have as their root cause, failure by the pilot to maintain flying
> speed or, stated more directly, control his angle of attack. Clearly, based
> on these r.a.s threads on the subject, some do not understand AOA in some
> fundamental way and that's chilling.
>
> Controlling airspeed is simply not good enough - it's too abstract, too easy
> to triviallize, too easy to misunderstand the significance of it.
>
> Safety committees and organizations need to take this to hart. Here is a
> root cause of our most dangerous accidents. The awareness of and
> understanding of AOA has somehow slipped through the cracks. Slay this
> dragon, and our accident numbers will look far better.
>
> If the concept and practice of controlling angle of attack is not absolutely
> ingrained in a pilot, the probability of an accident is non-trivial - in
> fact, sooner or later, it's a near certainty. Awareness of AOA should never
> be far from a pilots consiousness.
>
> Controlling angle of attack is so fundamental to being a pilot that it's
> staggering to think that it's possible to become one without it being
> hammered into them until it's as instinctive as walking. Flying an aircraft
> without this level of understanding is like being the captain of a ship
> without understanding what makes it float.
>
> As pilots, we do not fly the cockpit, the fuselage or the empenage - we fly
> the wing. The wing is really the only thing that does fly, the rest is just
> baggage.
>
> Read Jim Webb's truly excellent book "Fly the wing".http://www.amazon.com/Fly-Wing-James-Webb/dp/0813805414
>
> Or equally good, Wolfgang Langewiesche's "Stick and Rudder". You can read
> it free on line at Google Books.
>
> Read these books - please! There is simply no subject in aviation that is
> more fundamental or important to your survival.
>
> Bill Daniels

[[email protected]]

On Dec 11, 6:27 pm, "Bill Daniels" <bildan@comcast-dot-net> wrote:
> The threads on this subject has uncovered something that gives me chills.
>
> Internationaly, gliding has an abominable safety record. Many fatal
> accidents have as their root cause, failure by the pilot to maintain flying
> speed or, stated more directly, control his angle of attack. Clearly, based
> on these r.a.s threads on the subject, some do not understand AOA in some
> fundamental way and that's chilling.
>
> Controlling airspeed is simply not good enough - it's too abstract, too easy
> to triviallize, too easy to misunderstand the significance of it.
>
> Safety committees and organizations need to take this to hart. Here is a
> root cause of our most dangerous accidents. The awareness of and
> understanding of AOA has somehow slipped through the cracks. Slay this
> dragon, and our accident numbers will look far better.
>
> If the concept and practice of controlling angle of attack is not absolutely
> ingrained in a pilot, the probability of an accident is non-trivial - in
> fact, sooner or later, it's a near certainty. Awareness of AOA should never
> be far from a pilots consiousness.
>
> Controlling angle of attack is so fundamental to being a pilot that it's
> staggering to think that it's possible to become one without it being
> hammered into them until it's as instinctive as walking. Flying an aircraft
> without this level of understanding is like being the captain of a ship
> without understanding what makes it float.
>
> As pilots, we do not fly the cockpit, the fuselage or the empenage - we fly
> the wing. The wing is really the only thing that does fly, the rest is just
> baggage.
>
> Read Jim Webb's truly excellent book "Fly the wing".http://www.amazon.com/Fly-Wing-James-Webb/dp/0813805414
>
> Or equally good, Wolfgang Langewiesche's "Stick and Rudder". You can read
> it free on line at Google Books.
>
> Read these books - please! There is simply no subject in aviation that is
> more fundamental or important to your survival.
>
> Bill Daniels

Bill,

You are wasting your breath, in this case several strokes of keys.

Jacek
Pasco, WA

[Chris Wells]

Of course, it doesn't help that the AOA control is called an "elevator", leading one to believe that it makes you go up & down - I've also seen a zillion references in TV & the movies that reinforced this belief.

As far as I'm concerned, Stick & Rudder is the best book on piloting an aircraft ever written. I have a copy printed in 1944.

[Bob Whelan[_2_]]

Udo wrote:
> I broached a subject on the http://soaringcanada.riq.ca/ The Round
> Table but not with a direct question about A of A but more general, to
> see what the response was. I tought it was interesting and revealing.
> I ask "A question on minimizing stall accidents". I wanted to get a
> sense of how this critical phase was being taught, in light of an
> accident that happened just prior. If you want to see the answer you
> my want to read some of the comments.
> Udo
>
>
>
>
> On Dec 11, 9:27 pm, "Bill Daniels" <bildan@comcast-dot-net> wrote:
>> The threads on this subject has uncovered something that gives me chills.
>>
>> Internationaly, gliding has an abominable safety record. Many fatal
>> accidents have as their root cause, failure by the pilot to maintain flying
>> speed or, stated more directly, control his angle of attack. Clearly, based
>> on these r.a.s threads on the subject, some do not understand AOA in some
>> fundamental way and that's chilling.

When I went to collich in the U.S. (1967-1972), even though aeronautical
engineering (what I *really* wanted to major in) had morphed into
aerospace engineering (crummy commies), one forlorn airplane-based
course curricularly remained. Nonetheless, in that one (mostly a nearly
incomprehensible stability and control) aircraft-dominant course, it
became apparent to me that wings cared first about AoA, and only
secondarily about velocity of oncoming air. This was long before I'd
sat in a lightplane, seen a glider, or heard of (the very excellent)
"Stick and Rudder."

Soon after graduating, I bumbled into soaring, and the illness
permanently altered my life. Regrettably, I can no longer remember if
or how my instructor taught 'low speed flight' aspects. Can't remember
if he mentioned AoA, or if he merely said 'maintain flying speed.'

Doesn't matter, because the aforementioned course colored whatever my
instructor also conveyed.

In glider terms, if we assume compressibility isn't an issue (and it
isn't, for glider airspeeds), the wing cares Zero what speed your ASI
displays. Physically, it cares only about AoA of the oncoming air. Of
course, both are (through the stick) inter-related, but one (easier to
reliably measure) falls out in the wash, while the other (AoA),
physically determines what the wing is going to do next.

Now, (glider)pilot training reality demonstrably proves conceptual grasp
of the importance of AoA to the wing's immediate future actions (and
arguably, pilots' near-term lives) isn't required in order to obtain
one's pilot's license. Whether or not that's a good thing leads to this
thread's sort of 'religious arguments.' Fact is, cats can be skinned
multiple ways...

Personally, my brain is most comfortable understanding underlying
physical principles, even if it must (in part) rely on indirect
measurements (e.g. ASI, noise, 'feel,' etc.). I believe if a person
really and truly grasps the underlying physical principles governing the
consequences of his or her actions, s/he's more likely to do the
physically correct thing in moments of crisis, than not. Further,
s/he's less likely to (N.B. Key Word follows!) *inadvertently* go where
no thoughtful risk taker inadvertently wishes to go. (Kids, can you
spell "i*n-p*a*t*t*e*r*n s*t*a*l*l/s*p*i*n?")

Furthermore personally, I'd love to have an AoA gauge in my (flapped)
glider, even if NOT scientifically/numerically accurate. So long as
it's repeatable, I wouldn't care whether it showed my ship stalled at
10-degrees or 30-degrees AoA for 'whatever' flap deflection. That's the
difference between usable engineering accuracy, and scientific (e.g.
wind-tunnel-comparative) accuracy. Absence of the latter doesn't rule
out usefulness of the former.

'Reverently,'
Bob W.

[Tony Verhulst]

> As far as I'm concerned, Stick & Rudder is the best book on piloting
> an aircraft ever written. I have a copy printed in 1944.

I've heard (but not verified) that, next to the bible, Stick And Rudder
has been in continuous publication longer than any other book. My 1972
edition has 40 pages on what it takes to turn an airplane - and it's 40
pages that you *want* to read. Get this book if don't have it already!

Tony V. CFIG

[Bert Willing[_2_]]

Sorry Bill,

I don't know how you train your students, but the training I received, and
the training I give, ALWAYS refers to the attitude of the nose in respect to
the horizon, NEVER to ASI readings.
Nose attitude is the onboard AoA, and it works.

If in your environment the reference is ASI reading, then indeed this would
be indeed chilling.

On a winch launch, nose attitude does not work, but ASI reference does work.
Limits need to be greatly corrected in respect to free flight, but if you
don't get below this limit, you won't crash - because the limit is such that
you simply can't reach critical AoA by staying above the limit.

Bert

"Bill Daniels" <bildan@comcast-dot-net> wrote in message
. ..
> The threads on this subject has uncovered something that gives me chills.
>
> Internationaly, gliding has an abominable safety record. Many fatal
> accidents have as their root cause, failure by the pilot to maintain
> flying speed or, stated more directly, control his angle of attack.
> Clearly, based on these r.a.s threads on the subject, some do not
> understand AOA in some fundamental way and that's chilling.
>
> Controlling airspeed is simply not good enough - it's too abstract, too
> easy to triviallize, too easy to misunderstand the significance of it.
>
> Safety committees and organizations need to take this to hart. Here is a
> root cause of our most dangerous accidents. The awareness of and
> understanding of AOA has somehow slipped through the cracks. Slay this
> dragon, and our accident numbers will look far better.
>
> If the concept and practice of controlling angle of attack is not
> absolutely ingrained in a pilot, the probability of an accident is
> non-trivial - in fact, sooner or later, it's a near certainty. Awareness
> of AOA should never be far from a pilots consiousness.
>
> Controlling angle of attack is so fundamental to being a pilot that it's
> staggering to think that it's possible to become one without it being
> hammered into them until it's as instinctive as walking. Flying an
> aircraft without this level of understanding is like being the captain of
> a ship without understanding what makes it float.
>
> As pilots, we do not fly the cockpit, the fuselage or the empenage - we
> fly the wing. The wing is really the only thing that does fly, the rest
> is just baggage.
>
> Read Jim Webb's truly excellent book "Fly the wing".
> http://www.amazon.com/Fly-Wing-James-Webb/dp/0813805414
>
> Or equally good, Wolfgang Langewiesche's "Stick and Rudder". You can read
> it free on line at Google Books.
>
> Read these books - please! There is simply no subject in aviation that is
> more fundamental or important to your survival.
>
> Bill Daniels
>

[Scott[_1_]]

This is an interesting topic. How exactly does the horizon give you
angle of attack reference? I don't have much experience in gliders yet,
but in powered airplanes, the horizon can be in a lot of different
places with reference to the nose. For example, the nose might be
slightly above the horizon at stall with engine at idle, a lot more
above the horizon at stall with full power and the horizon might be
straight above the cockpit while holding a stall in a spin. In a
powered plane, the nose can be right on the horizon, but airspeed may be
just above stall as you are "mushing" through the air (ie level attitude
with reference to horizon, but sinking at a high rate). I was taught
that angle of attack was the angular difference between the wing chord
line and the wind flow direction. I would think a simple AoA indicator
would be a string suspended below a wire about 1 to 2 feet out in front
of the wing with a panel outboard of the string with lines drawn
representing angles drawn with a protractor such as 0 degrees, 5
degrees, 12 degrees, etc.


Scott


Bert Willing wrote:
> Sorry Bill,
>
> I don't know how you train your students, but the training I received, and
> the training I give, ALWAYS refers to the attitude of the nose in respect to
> the horizon, NEVER to ASI readings.
> Nose attitude is the onboard AoA, and it works.
>
> If in your environment the reference is ASI reading, then indeed this would
> be indeed chilling.
>
> On a winch launch, nose attitude does not work, but ASI reference does work.
> Limits need to be greatly corrected in respect to free flight, but if you
> don't get below this limit, you won't crash - because the limit is such that
> you simply can't reach critical AoA by staying above the limit.
>
> Bert
>
> "Bill Daniels" <bildan@comcast-dot-net> wrote in message
> . ..
>
>>The threads on this subject has uncovered something that gives me chills.
>>
>>Internationaly, gliding has an abominable safety record. Many fatal
>>accidents have as their root cause, failure by the pilot to maintain
>>flying speed or, stated more directly, control his angle of attack.
>>Clearly, based on these r.a.s threads on the subject, some do not
>>understand AOA in some fundamental way and that's chilling.
>>
>>Controlling airspeed is simply not good enough - it's too abstract, too
>>easy to triviallize, too easy to misunderstand the significance of it.
>>
>>Safety committees and organizations need to take this to hart. Here is a
>>root cause of our most dangerous accidents. The awareness of and
>>understanding of AOA has somehow slipped through the cracks. Slay this
>>dragon, and our accident numbers will look far better.
>>
>>If the concept and practice of controlling angle of attack is not
>>absolutely ingrained in a pilot, the probability of an accident is
>>non-trivial - in fact, sooner or later, it's a near certainty. Awareness
>>of AOA should never be far from a pilots consiousness.
>>
>>Controlling angle of attack is so fundamental to being a pilot that it's
>>staggering to think that it's possible to become one without it being
>>hammered into them until it's as instinctive as walking. Flying an
>>aircraft without this level of understanding is like being the captain of
>>a ship without understanding what makes it float.
>>
>>As pilots, we do not fly the cockpit, the fuselage or the empenage - we
>>fly the wing. The wing is really the only thing that does fly, the rest
>>is just baggage.
>>
>>Read Jim Webb's truly excellent book "Fly the wing".
>>http://www.amazon.com/Fly-Wing-James-Webb/dp/0813805414
>>
>>Or equally good, Wolfgang Langewiesche's "Stick and Rudder". You can read
>>it free on line at Google Books.
>>
>>Read these books - please! There is simply no subject in aviation that is
>>more fundamental or important to your survival.
>>
>>Bill Daniels
>>
>
>
>

--
Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)

[Bill Daniels]

Exibit "A" below. I couldn't come up with a better example of what I'm
talking about.

"Bert Willing" > wrote in message
...
> Sorry Bill,
>
> I don't know how you train your students, but the training I received, and
> the training I give, ALWAYS refers to the attitude of the nose in respect
> to the horizon, NEVER to ASI readings.
> Nose attitude is the onboard AoA, and it works.
>
> If in your environment the reference is ASI reading, then indeed this
> would be indeed chilling.
>
> On a winch launch, nose attitude does not work, but ASI reference does
> work. Limits need to be greatly corrected in respect to free flight, but
> if you don't get below this limit, you won't crash - because the limit is
> such that you simply can't reach critical AoA by staying above the limit.
>
> Bert
>
> "Bill Daniels" <bildan@comcast-dot-net> wrote in message
> . ..
>> The threads on this subject has uncovered something that gives me chills.
>>
>> Internationaly, gliding has an abominable safety record. Many fatal
>> accidents have as their root cause, failure by the pilot to maintain
>> flying speed or, stated more directly, control his angle of attack.
>> Clearly, based on these r.a.s threads on the subject, some do not
>> understand AOA in some fundamental way and that's chilling.
>>
>> Controlling airspeed is simply not good enough - it's too abstract, too
>> easy to triviallize, too easy to misunderstand the significance of it.
>>
>> Safety committees and organizations need to take this to hart. Here is a
>> root cause of our most dangerous accidents. The awareness of and
>> understanding of AOA has somehow slipped through the cracks. Slay this
>> dragon, and our accident numbers will look far better.
>>
>> If the concept and practice of controlling angle of attack is not
>> absolutely ingrained in a pilot, the probability of an accident is
>> non-trivial - in fact, sooner or later, it's a near certainty. Awareness
>> of AOA should never be far from a pilots consiousness.
>>
>> Controlling angle of attack is so fundamental to being a pilot that it's
>> staggering to think that it's possible to become one without it being
>> hammered into them until it's as instinctive as walking. Flying an
>> aircraft without this level of understanding is like being the captain of
>> a ship without understanding what makes it float.
>>
>> As pilots, we do not fly the cockpit, the fuselage or the empenage - we
>> fly the wing. The wing is really the only thing that does fly, the rest
>> is just baggage.
>>
>> Read Jim Webb's truly excellent book "Fly the wing".
>> http://www.amazon.com/Fly-Wing-James-Webb/dp/0813805414
>>
>> Or equally good, Wolfgang Langewiesche's "Stick and Rudder". You can
>> read it free on line at Google Books.
>>
>> Read these books - please! There is simply no subject in aviation that
>> is more fundamental or important to your survival.
>>
>> Bill Daniels
>>
>
>

[toad]

On Dec 13, 7:10 am, Scott > wrote:
> This is an interesting topic. How exactly does the horizon give you
> angle of attack reference?

It does NOT give an angle of attack reference.

The pitch attitude (horizon) differs from AOA by the climb angle. See
http://www.av8n.com/how/htm/aoa.html for a good explanation.


While I agree that understanding of AOA is crucial for a pilot. I
don't think that a AOA indicator would be very useful in gliders.
(except for flight testing of a new design)

I think that stall accidents are caused by lack of awareness and lack
of attention. Letting the airspeed "creep away" and incorrectly
responding to the loss of airspeed. Substituting an AOA dial for the
airspeed dial, won't change that.


AOA gauges seem best suited for heavy aircraft flown by reference to
instruments. Where you might have to wait a couple of minutes after
setting the AOA and power lever to get the airspeed to respond.
Gliders will change their airspeed much quicker than a 747 or F-14.
We also only really fly at 2 or 3 different weights. No ballast, half
or full. So we only really have to remember the best L/D speed for
these conditions.

Todd Smith
3S

[Eric Greenwell]

Bill Daniels wrote:

> Controlling airspeed is simply not good enough - it's too abstract, too easy
> to triviallize, too easy to misunderstand the significance of it.

snip
>
> As pilots, we do not fly the cockpit, the fuselage or the empenage - we fly
> the wing. The wing is really the only thing that does fly, the rest is just
> baggage.

While I agree with Bill that stalling the wing is a proximate cause of
stall/spin accidents, I don't understand his conclusion that getting
pilots to understand angle of attack (AOA) will help a lot (or even at
all). The big problem is AOA is an abstract engineering parameter,
because pilots can't see it, can't hear it, and can't feel it. We can
see attitude and airpeed, we can hear airspeed and stall rumble, and we
can feel stick position and stick forces, so that is what we use to fly
by. I sure don't think about AOA when I'm flying.

IF we had a "good" AOA indicator or pre-stall indicator, THEN we might
be able to fly more safely using it. And that is something the soaring
community has wanted for decades, but so far, we don't have any in wide
use. So, I think we need people to experiment with currently available
AOA units, like Safeflight's and DG's. If they seem useful, try them on
students, and see if students learn fly more safely or more quickly. If
AOA indicators seem promising, it might lead to better/cheaper
indicators, and begin to spread throughout the fleet.

Until we can hear it, see it, or feel it, we won't be able to use.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[Bob Kuykendall]

On Dec 13, 2:16 am, "Bert Willing" <bw_no_spam_ple...@tango-
whisky.com> wrote:

>... Nose attitude is the onboard AoA, and it works...

Apologies for the dogpile, but I think that's wrong and wrong. I
believe that thinking like that is exactly what leads to the types of
insidious stall/spin entries that most often become accidents.

That's not to say that nose angle isn't a useful tool. In straight-and-
level flight, and in stable coordinated turns, nose angle and nose
angle rate are key indicators of speed and acceleration.

However, straight-and-level flight and stable coordinated turns
constitute a very small subset of the available flight regimes, and
are among those least likely to offer unanticipated stall spin
entries.

Also, in flapped ships, and especially in glidepath-flapped ships,
nose angle is virtually useless as a speed reference independent of
flap deflection. In a good old HP glider, you can have your toes on
the horizon and be tearing along at a stable 80 kts. Or you can be
going almost straight down at a stable 80 kts and viewing the horizon
through the crown of the canopy.

So far as soaring and sailplanes go, I'm basically an anti-
gadgetarian. For years, the most complicated device in my ship was the
digital clock. However, I think that a simple, effective AOA indicator
with an intuitive display would be a real asset. And, it would be
useful not only for stall/spin protection but also for cruise and
thermal optimization.

Thanks, Bob K.

[bumper]

I'm getting pretty tired of all this "Angle of Attack" business.

As a pacifist (I abhor violence when it's directed at me) I would prefer we
use the term, "Angle of Retreat" instead.

Remember, fly the tail, the wing will take care of itself.

bumper
"Dare to be different . . . circle in sink."
zz
Minden
purveyor of Quiet Vents and MKII (non AOA) yaw strings.
"Bob Kuykendall" > wrote in message
...
> On Dec 13, 2:16 am, "Bert Willing" <bw_no_spam_ple...@tango-
> whisky.com> wrote:
>
>>... Nose attitude is the onboard AoA, and it works...
>
> Apologies for the dogpile, but I think that's wrong and wrong. I
> believe that thinking like that is exactly what leads to the types of
> insidious stall/spin entries that most often become accidents.
>
> That's not to say that nose angle isn't a useful tool. In straight-and-
> level flight, and in stable coordinated turns, nose angle and nose
> angle rate are key indicators of speed and acceleration.
>
> However, straight-and-level flight and stable coordinated turns
> constitute a very small subset of the available flight regimes, and
> are among those least likely to offer unanticipated stall spin
> entries.
>
> Also, in flapped ships, and especially in glidepath-flapped ships,
> nose angle is virtually useless as a speed reference independent of
> flap deflection. In a good old HP glider, you can have your toes on
> the horizon and be tearing along at a stable 80 kts. Or you can be
> going almost straight down at a stable 80 kts and viewing the horizon
> through the crown of the canopy.
>
> So far as soaring and sailplanes go, I'm basically an anti-
> gadgetarian. For years, the most complicated device in my ship was the
> digital clock. However, I think that a simple, effective AOA indicator
> with an intuitive display would be a real asset. And, it would be
> useful not only for stall/spin protection but also for cruise and
> thermal optimization.
>
> Thanks, Bob K.

[Scott[_1_]]

Hey Bob, quick question for you...I seem to recall hearing during
powered flight training that says a wing will always stall at a fixed
angle of attack, regardless of what the airspeed is. I think it was
said this is regardless of loading, airspeed, etc. If this IS true, AoA
indicators might be useful, especially if an indicator is on the
instrument panel and maybe, if it were a simple bar graph of different
colored LEDs, one could calibrate it to give an audible stall warning
horn...whatcha think???

Scott
Corben Junior Ace (limited glider time!)

Bob Kuykendall wrote:
> On Dec 13, 2:16 am, "Bert Willing" <bw_no_spam_ple...@tango-
> whisky.com> wrote:
>
>
>>... Nose attitude is the onboard AoA, and it works...
>
>
> Apologies for the dogpile, but I think that's wrong and wrong. I
> believe that thinking like that is exactly what leads to the types of
> insidious stall/spin entries that most often become accidents.
>
> That's not to say that nose angle isn't a useful tool. In straight-and-
> level flight, and in stable coordinated turns, nose angle and nose
> angle rate are key indicators of speed and acceleration.
>
> However, straight-and-level flight and stable coordinated turns
> constitute a very small subset of the available flight regimes, and
> are among those least likely to offer unanticipated stall spin
> entries.
>
> Also, in flapped ships, and especially in glidepath-flapped ships,
> nose angle is virtually useless as a speed reference independent of
> flap deflection. In a good old HP glider, you can have your toes on
> the horizon and be tearing along at a stable 80 kts. Or you can be
> going almost straight down at a stable 80 kts and viewing the horizon
> through the crown of the canopy.
>
> So far as soaring and sailplanes go, I'm basically an anti-
> gadgetarian. For years, the most complicated device in my ship was the
> digital clock. However, I think that a simple, effective AOA indicator
> with an intuitive display would be a real asset. And, it would be
> useful not only for stall/spin protection but also for cruise and
> thermal optimization.
>
> Thanks, Bob K.

--
Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)

[HL Falbaum]

By Golly---I think you are on to something here!
See post by Mike Borgelt on the other, related, thread.

Hartley Falbaum
KF Georgia USA


"bumper" > wrote in message
...
> I'm getting pretty tired of all this "Angle of Attack" business.
>
>
> Remember, fly the tail, the wing will take care of itself.
>
> bumper
> "Dare to be different . . . circle in sink."
> zz
> Minden
> purveyor of Quiet Vents and MKII (non AOA) yaw strings.

[Wayne Paul]

Scott,

It is true. A wing stalls for a given angle of attack for a given flap
setting. It is not dependent on wing loading, attitude, etc. The index
system you described exists on US Naval aircraft. Depending on the
aircraft, it is either mounted on the glare shield or the HUD. In either
case, it is visible while looking out the windscreen. In addition an
external set of lights showing AOA are placed such that they can be seen by
the LSO (Landing Signals Officer) on the flight deck.

Of all the instruments in the A-3B and A-6A , the AOA is the only one I
would like to add to my HP-14.

Wayne
HP-14 "6F"
http://www.soaridaho.com/Schreder/HP-14/N990/N990.html



"Scott" > wrote in message
.. .
> Hey Bob, quick question for you...I seem to recall hearing during powered
> flight training that says a wing will always stall at a fixed angle of
> attack, regardless of what the airspeed is. I think it was said this is
> regardless of loading, airspeed, etc. If this IS true, AoA indicators
> might be useful, especially if an indicator is on the instrument panel and
> maybe, if it were a simple bar graph of different colored LEDs, one could
> calibrate it to give an audible stall warning horn...whatcha think???
>
> Scott
> Corben Junior Ace (limited glider time!)
>
> Bob Kuykendall wrote:
>> On Dec 13, 2:16 am, "Bert Willing" <bw_no_spam_ple...@tango-
>> whisky.com> wrote:
>>
>>
>>>... Nose attitude is the onboard AoA, and it works...
>>
>>
>> Apologies for the dogpile, but I think that's wrong and wrong. I
>> believe that thinking like that is exactly what leads to the types of
>> insidious stall/spin entries that most often become accidents.
>>
>> That's not to say that nose angle isn't a useful tool. In straight-and-
>> level flight, and in stable coordinated turns, nose angle and nose
>> angle rate are key indicators of speed and acceleration.
>>
>> However, straight-and-level flight and stable coordinated turns
>> constitute a very small subset of the available flight regimes, and
>> are among those least likely to offer unanticipated stall spin
>> entries.
>>
>> Also, in flapped ships, and especially in glidepath-flapped ships,
>> nose angle is virtually useless as a speed reference independent of
>> flap deflection. In a good old HP glider, you can have your toes on
>> the horizon and be tearing along at a stable 80 kts. Or you can be
>> going almost straight down at a stable 80 kts and viewing the horizon
>> through the crown of the canopy.
>>
>> So far as soaring and sailplanes go, I'm basically an anti-
>> gadgetarian. For years, the most complicated device in my ship was the
>> digital clock. However, I think that a simple, effective AOA indicator
>> with an intuitive display would be a real asset. And, it would be
>> useful not only for stall/spin protection but also for cruise and
>> thermal optimization.
>>
>> Thanks, Bob K.
>
> --
> Scott
> http://corbenflyer.tripod.com/
> Gotta Fly or Gonna Die
> Building RV-4 (Super Slow Build Version)

[Scott[_1_]]

If they're good enough for the squids, they're good enough for me! ;)

When I was in the USAF, I think I recall seeing moveable vanes on the
side of the fuselage on C-135 types (I assume they were AoA senders)...

Scott

Wayne Paul wrote:
> Scott,
>
> It is true. A wing stalls for a given angle of attack for a given flap
> setting. It is not dependent on wing loading, attitude, etc. The index
> system you described exists on US Naval aircraft. Depending on the
> aircraft, it is either mounted on the glare shield or the HUD. In either
> case, it is visible while looking out the windscreen. In addition an
> external set of lights showing AOA are placed such that they can be seen by
> the LSO (Landing Signals Officer) on the flight deck.
>
> Of all the instruments in the A-3B and A-6A , the AOA is the only one I
> would like to add to my HP-14.
>
> Wayne
> HP-14 "6F"
> http://www.soaridaho.com/Schreder/HP-14/N990/N990.html
>
>
>
> "Scott" > wrote in message
> .. .
>
>>Hey Bob, quick question for you...I seem to recall hearing during powered
>>flight training that says a wing will always stall at a fixed angle of
>>attack, regardless of what the airspeed is. I think it was said this is
>>regardless of loading, airspeed, etc. If this IS true, AoA indicators
>>might be useful, especially if an indicator is on the instrument panel and
>>maybe, if it were a simple bar graph of different colored LEDs, one could
>>calibrate it to give an audible stall warning horn...whatcha think???
>>
>>Scott
>>Corben Junior Ace (limited glider time!)
>>
>>Bob Kuykendall wrote:
>>
>>>On Dec 13, 2:16 am, "Bert Willing" <bw_no_spam_ple...@tango-
>>>whisky.com> wrote:
>>>
>>>
>>>
>>>>... Nose attitude is the onboard AoA, and it works...
>>>
>>>
>>>Apologies for the dogpile, but I think that's wrong and wrong. I
>>>believe that thinking like that is exactly what leads to the types of
>>>insidious stall/spin entries that most often become accidents.
>>>
>>>That's not to say that nose angle isn't a useful tool. In straight-and-
>>>level flight, and in stable coordinated turns, nose angle and nose
>>>angle rate are key indicators of speed and acceleration.
>>>
>>>However, straight-and-level flight and stable coordinated turns
>>>constitute a very small subset of the available flight regimes, and
>>>are among those least likely to offer unanticipated stall spin
>>>entries.
>>>
>>>Also, in flapped ships, and especially in glidepath-flapped ships,
>>>nose angle is virtually useless as a speed reference independent of
>>>flap deflection. In a good old HP glider, you can have your toes on
>>>the horizon and be tearing along at a stable 80 kts. Or you can be
>>>going almost straight down at a stable 80 kts and viewing the horizon
>>>through the crown of the canopy.
>>>
>>>So far as soaring and sailplanes go, I'm basically an anti-
>>>gadgetarian. For years, the most complicated device in my ship was the
>>>digital clock. However, I think that a simple, effective AOA indicator
>>>with an intuitive display would be a real asset. And, it would be
>>>useful not only for stall/spin protection but also for cruise and
>>>thermal optimization.
>>>
>>>Thanks, Bob K.
>>
>>--
>>Scott
>>http://corbenflyer.tripod.com/
>>Gotta Fly or Gonna Die
>>Building RV-4 (Super Slow Build Version)
>
>
>

--
Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)

[Chris Wells]

As far as I'm concerned, Stick & Rudder is the best book on piloting
an aircraft ever written. I have a copy printed in 1944.

I've heard (but not verified) that, next to the bible, Stick And Rudder
has been in continuous publication longer than any other book. My 1972
edition has 40 pages on what it takes to turn an airplane - and it's 40
pages that you *want* to read. Get this book if don't have it already!

Tony V. CFIG

What about "Extraordinary Popular Delusions and the Madness of Crowds"? That's still in print...

[Bob Kuykendall]

On Dec 14, 5:41 am, Chris Wells <Chris.Wells.
> wrote:

> What about "Extraordinary Popular Delusions and the Madness of
> Crowds"? That's still in print...

In print? Heck, this is RAS. We practice it daily here.

Bob K.

[hans]

Until I read the book 'Ruder and Stick' I thought you can not hear the
AoA. But now I know that I can hear large changes in the AoA. Just turn
down the radio and the variometer and listen to your glider when you are
flying at different AoA at the same speed. You will realize marked
differences in sound of your gilder. Our Duo sounds different at
thermaling AoA and at stall AoA. The sound at stall AoA is much deeper
than at thermaling AoA.

You can feel the distance to the stalling AoA in the elevator. If you
are far away from the stall AoA a small increase in back pressure on the
stick will lead to a much larger change of the attitude than at an AoA
close to stall speed.

Unfortunately we train our students in practical flying for attitude
controlled flight. This is a very successful strategy to reach an
intended equilibrium speed in calm air if a slow control loop is
sufficient to reach the equilibrium. But it is not a very good technique
to fly in the turbulent air close to a ridge. There as in winch launch
we train to rely more in the ASI, but again this is just a successful
technique, if a slow control loop is sufficient to reach the equilibrium.

It would be much better to have a fast AoA in the glider and to use it
in the control loop, because it would tell you all the time how far you
are away from the stalling AoA.


Eric Greenwell schrieb:
> Bill Daniels wrote:
>
>> Controlling airspeed is simply not good enough - it's too abstract,
>> too easy to triviallize, too easy to misunderstand the significance of
>> it.
>
> snip
>>
>> As pilots, we do not fly the cockpit, the fuselage or the empenage -
>> we fly the wing. The wing is really the only thing that does fly, the
>> rest is just baggage.
>
> While I agree with Bill that stalling the wing is a proximate cause of
> stall/spin accidents, I don't understand his conclusion that getting
> pilots to understand angle of attack (AOA) will help a lot (or even at
> all). The big problem is AOA is an abstract engineering parameter,
> because pilots can't see it, can't hear it, and can't feel it. We can
> see attitude and airpeed, we can hear airspeed and stall rumble, and we
> can feel stick position and stick forces, so that is what we use to fly
> by. I sure don't think about AOA when I'm flying.
>
> IF we had a "good" AOA indicator or pre-stall indicator, THEN we might
> be able to fly more safely using it. And that is something the soaring
> community has wanted for decades, but so far, we don't have any in wide
> use. So, I think we need people to experiment with currently available
> AOA units, like Safeflight's and DG's. If they seem useful, try them on
> students, and see if students learn fly more safely or more quickly. If
> AOA indicators seem promising, it might lead to better/cheaper
> indicators, and begin to spread throughout the fleet.
>
> Until we can hear it, see it, or feel it, we won't be able to use.
>

[Chris Wells]

Until I read the book 'Ruder and Stick' I thought you can not hear the
AoA. But now I know that I can hear large changes in the AoA. Just turn
down the radio and the variometer and listen to your glider when you are
flying at different AoA at the same speed. You will realize marked
differences in sound of your gilder. Our Duo sounds different at
thermaling AoA and at stall AoA. The sound at stall AoA is much deeper
than at thermaling AoA.

You can feel the distance to the stalling AoA in the elevator. If you
are far away from the stall AoA a small increase in back pressure on the
stick will lead to a much larger change of the attitude than at an AoA
close to stall speed.





This is exactly how I learned to fly hang gliders. I mostly use my ears, but the bar pressure is also important. It also helps to have a helmet with earholes in it - you can sometimes hear which side the thermal is on. An important difference between planes & hang gliders is that the trim is always set at the same speed, so you can tell if you're at min sink or best glide using bar pressure.

[J a c k[_2_]]

Eric Greenwell wrote:


> The big problem is AOA is an abstract engineering parameter,
> because pilots can't see it, can't hear it, and can't feel it. We can
> see attitude and airpeed...

The only airspeed I've ever "seen" in a glider was indicated on the face
of the mechanical ASI--a rather remote approximation--and as a sole
indication of stalling speed can be hugely misleading. AOA, within the
limitations of the instrument and the installation, is never wrong--no
matter the speed, g-loading, or aircraft weight.


> ...we can hear airspeed and stall rumble, and we
> can feel stick position and stick forces, so that is what we use to fly
> by. I sure don't think about AOA when I'm flying.

You would if you had an AOA to think about. In its absence you have
learned to substitute those other vague indications, some of which are
present in some situations but not in others, and some of which, though
present, are of little use in any but the narrowest of circumstances.
Don't knock AOA until you've used it.


> Until we can hear it, see it, or feel it, we won't be able to use [it].

And until you use it, you won't be able to hear, see, or feel it.

It's basically the difference between a (ASI) love letter and a (AOA)
caress. I know which I prefer, especially when time is of the
essence--which it is anytime an object is in motion.


Jack

[J a c k[_2_]]

toad wrote:


> While I agree that understanding of AOA is crucial for a pilot. I
> don't think that a AOA indicator would be very useful in gliders


Why would the best reference for the actual performance of the aircraft
be less desirable than an error-prone and very approximate indication
which, like a stopped clock, is exactly right about twice a day?



> I think that stall accidents are caused by lack of awareness and lack
> of attention. Letting the airspeed "creep away" and incorrectly
> responding to the loss of airspeed. Substituting an AOA dial for the
> airspeed dial, won't change that.


It is my understanding that one is supposed to be able to fly a glider
safely without reference to the ASI, and I suppose that should also then
apply to AOA as well. Obviously, not everyone can do so. And there are a
few each year that manage to demonstrate the inability to fly safely in
spite of the availability of a working ASI. It is also possible that the
fact that the stall speed of a given sailplane on a given flight could
be +/- 15%, or more, from book speed _in one-g flight_ should be given
more thorough consideration. Do we know then what it might be in a 30-60
degree banked final turn, or in a wind shear condition where the ASI
reads considerably below the book stalling speed? "More" is an answer,
in one case, and "Less" in the other. How much more or less we find by
trial and error, guesswork and luck--or not. An AOA would tell us
instantly and throughout the normal operating range of the glider, and
beyond, just how close to the stall we are operating.



> AOA gauges seem best suited for heavy aircraft flown by reference to
> instruments. Where you might have to wait a couple of minutes after
> setting the AOA and power lever to get the airspeed to respond.
> Gliders will change their airspeed much quicker than a 747 or F-14.


I can't use the F-14 or the 747 as a reference, because I have not flown
either. My understanding is that the F-14 can accelerate rather rapidly
and slow down pretty quickly as well. High performance military aircraft
which I have flown certainly exhibited that capability. To say that any
of them, or even a 747, could not accelerate more rapidly than an
unpowered glider in a specified attitude seems an incompletely
considered statement, but perhaps you can provide some evidence to
support your claim.



> We also only really fly at 2 or 3 different weights. So we only
> really have to remember the best L/D speed for these conditions.

Be my guest--memorize as many speeds as you like. You'll still be
guessing at how close your ASI is to the actual stalling speed at any
particular moment. AOA never lies: any g-load; any altitude; any
attitude; any airspeed.



Jack

[Eric Greenwell]

J a c k wrote:
> Eric Greenwell wrote:
> > The big problem is AOA is an abstract engineering parameter,
>> because pilots can't see it, can't hear it, and can't feel it. We can
>> see attitude and airpeed...
>
> The only airspeed I've ever "seen" in a glider was indicated on the face
> of the mechanical ASI--a rather remote approximation--

The AIS is close enough, except in a slip, because doesn't have to be
accurate, just consistent. The flight manual values are based on what it
shows, not what the actual airspeed is.

> and as a sole
> indication of stalling speed can be hugely misleading.

Indeed, and that's why we use other indications in addition.

> AOA, within the
> limitations of the instrument and the installation, is never wrong--no
> matter the speed, g-loading, or aircraft weight.

In fact, the AOA instrument on every glider I've owned (six) was always
"wrong", because none of them had one. I like the idea, but the reality
is I've never had one, so I've never used one. Ditto for most pilots
when flying gliders.

>
>> ...we can hear airspeed and stall rumble, and we can feel stick
>> position and stick forces, so that is what we use to fly by. I sure
>> don't think about AOA when I'm flying.
>
> You would if you had an AOA to think about.

Well, yeah, but I don't.

> In its absence you have
> learned to substitute those other vague indications

I never had an AOA indicator, so I didn't learn to "substitute" for it,
I learned the vague indications from the very beginning. IF a suitable
AOA indicator became available in my glider, I would probably learn to
substitute it for the vague indications. Or maybe not - I don't know how
much value it would have for my flying until I try it.


> , some of which are
> present in some situations but not in others, and some of which, though
> present, are of little use in any but the narrowest of circumstances.

On the contrary, the "vague indications" have served me well for 5000+
hours of flying cross country!

> Don't knock AOA until you've used it.

I have never knocked AOA indicators as a *potentially* useful device. I
like the idea. I am skeptical that teaching pilots about AOA will reduce
accidents, as Bill suggested, UNLESS we have an AOA indicator for them
to look at (or hear/feel). I haven't seen any documentation that AOA
will improve safety or performance significantly, just personal opinions
that it will, so I am skeptical of enthusiastic claims that it will do so.

>
>
>> Until we can hear it, see it, or feel it, we won't be able to use [it].
>
> And until you use it, you won't be able to hear, see, or feel it.
>
> It's basically the difference between a (ASI) love letter and a (AOA)
> caress. I know which I prefer, especially when time is of the
> essence--which it is anytime an object is in motion.

Which one do you use in your glider, and where can I get one for my glider?

We need to have units in gliders, in use, before we can make any serious
claims about it's effectiveness. It seems like it should help, but so
far, the people that have used them were flying jets. Apparently, it's
essential in then environment, but jets aren't gliders. so we still
don't know.

I hope some pilots will try the Safeflight unit and the DG unit (and
others I'm not aware of), and report their experiences. If the reports
are positive, it might spur further use and lead to improved units, and
the best techniques for using them.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[Eric Greenwell]

> Be my guest--memorize as many speeds as you like. You'll still be
> guessing at how close your ASI is to the actual stalling speed at any
> particular moment. AOA never lies: any g-load; any altitude; any
> attitude; any airspeed.

While I think an AOA indicator might be useful, isn't this over selling
it's ability? How about with ice, rain, or bugs on the wing - is the
stalling AOA still the same? Does the AOA indicator read correctly in
slip? Does it read the AOA of the inboard tip and the outboard tip in a
turn? What if it freezes, or gets water it?

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

[Bert Willing[_2_]]

Sorry Bob,

I can't agree to that.
In level flight and coordinated turns, the nose attitude as an absolute
reference for the AoA for a given flap setting.
Most stall/spin entries happen exactly in this configuration (at least here
in Europe, maybe in the US you die differently) when people fly at critical
AoA close to the ground and then initiate a turn.
On flapped gliders, this happens with the flaps in thermal position, so who
cares about the AoA for the other flap positions? Haven't heared of any
fatal stall accident where the flaps have been at -10 degree...
If a pilot isn't aware that the nose is too high, why the hell would he care
what an AoA meter tells him?

Bert

"Bob Kuykendall" > wrote in message
...
> On Dec 13, 2:16 am, "Bert Willing" <bw_no_spam_ple...@tango-
> whisky.com> wrote:
>
>>... Nose attitude is the onboard AoA, and it works...
>
> Apologies for the dogpile, but I think that's wrong and wrong. I
> believe that thinking like that is exactly what leads to the types of
> insidious stall/spin entries that most often become accidents.
>
> That's not to say that nose angle isn't a useful tool. In straight-and-
> level flight, and in stable coordinated turns, nose angle and nose
> angle rate are key indicators of speed and acceleration.
>
> However, straight-and-level flight and stable coordinated turns
> constitute a very small subset of the available flight regimes, and
> are among those least likely to offer unanticipated stall spin
> entries.
>
> Also, in flapped ships, and especially in glidepath-flapped ships,
> nose angle is virtually useless as a speed reference independent of
> flap deflection. In a good old HP glider, you can have your toes on
> the horizon and be tearing along at a stable 80 kts. Or you can be
> going almost straight down at a stable 80 kts and viewing the horizon
> through the crown of the canopy.
>
> So far as soaring and sailplanes go, I'm basically an anti-
> gadgetarian. For years, the most complicated device in my ship was the
> digital clock. However, I think that a simple, effective AOA indicator
> with an intuitive display would be a real asset. And, it would be
> useful not only for stall/spin protection but also for cruise and
> thermal optimization.
>
> Thanks, Bob K.

[J a c k[_2_]]

Eric Greenwell wrote:
>
>> Be my guest--memorize as many speeds as you like. You'll still be
>> guessing at how close your ASI is to the actual stalling speed at any
>> particular moment. AOA never lies: any g-load; any altitude; any
>> attitude; any airspeed.
>
> While I think an AOA indicator might be useful, isn't this over selling
> it's ability? How about with ice, rain, or bugs on the wing - is the
> stalling AOA still the same? Does the AOA indicator read correctly in
> slip? Does it read the AOA of the inboard tip and the outboard tip in a
> turn? What if it freezes, or gets water it?


See both Daniels' and Pfeiffer's recent comments in the nearby "AoA Keep
it Going" thread.


Jack

[fred]

On Dec 16, 8:06 pm, J a c k > wrote:
> toad wrote:
> > While I agree that understanding of AOA is crucial for a pilot. I
> > don't think that a AOA indicator would be very useful in gliders
>
> Why would the best reference for the actual performance of the aircraft
> be less desirable than an error-prone and very approximate indication
> which, like a stopped clock, is exactly right about twice a day?
>
> > I think that stall accidents are caused by lack of awareness and lack
> > of attention. Letting the airspeed "creep away" and incorrectly
> > responding to the loss of airspeed. Substituting an AOA dial for the
> > airspeed dial, won't change that.
>
> It is my understanding that one is supposed to be able to fly a glider
> safely without reference to the ASI, and I suppose that should also then
> apply to AOA as well. Obviously, not everyone can do so. And there are a
> few each year that manage to demonstrate the inability to fly safely in
> spite of the availability of a working ASI. It is also possible that the
> fact that the stall speed of a given sailplane on a given flight could
> be +/- 15%, or more, from book speed _in one-g flight_ should be given
> more thorough consideration. Do we know then what it might be in a 30-60
> degree banked final turn, or in a wind shear condition where the ASI
> reads considerably below the book stalling speed? "More" is an answer,
> in one case, and "Less" in the other. How much more or less we find by
> trial and error, guesswork and luck--or not. An AOA would tell us
> instantly and throughout the normal operating range of the glider, and
> beyond, just how close to the stall we are operating.
>
> > AOA gauges seem best suited for heavy aircraft flown by reference to
> > instruments. Where you might have to wait a couple of minutes after
> > setting the AOA and power lever to get the airspeed to respond.
> > Gliders will change their airspeed much quicker than a 747 or F-14.
>
> I can't use the F-14 or the 747 as a reference, because I have not flown
> either. My understanding is that the F-14 can accelerate rather rapidly
> and slow down pretty quickly as well. High performance military aircraft
> which I have flown certainly exhibited that capability. To say that any
> of them, or even a 747, could not accelerate more rapidly than an
> unpowered glider in a specified attitude seems an incompletely
> considered statement, but perhaps you can provide some evidence to
> support your claim.
>
> > We also only really fly at 2 or 3 different weights. So we only
> > really have to remember the best L/D speed for these conditions.
>
> Be my guest--memorize as many speeds as you like. You'll still be
> guessing at how close your ASI is to the actual stalling speed at any
> particular moment. AOA never lies: any g-load; any altitude; any
> attitude; any airspeed.
>
> Jack

AOA is my favorite subject to teach. It is not easy but is a life
saver. Most pilots really don't understand relative wind. Ask them to
explain it. What happens when a gust is encountered + or -? Near a
stall the asi pitot tube is at an angle to the wind and is less
accurate. I use a pieceof yarn taped to the side od the canopy with a
"normal" air flow line marked. A the moment of the stall, the string
rises as you approach the stall. It is only a cheap teaching aid. I
probe my students understanding of why and where does the AOA COME
FROM AND WHY. Lift depends on speed of the air and angle of
attack...and it varies in many ways. At altitude, my students get a
lot of slow flight experience. They know! Fred