Stall strips vs. Washout

[k***@yahoo.com]

I've noticed a lot of aircraft are designed to use washout at the tips
to control stall behaviour. The idea as it was explained was that they
wanted the inboard part of the wing to stall before the outboard part
so aileron authority could be maintained a little longer.

I've also seen mention of stall strips being installed inboard to try
to affect the same thing.

It seems to me that trying to impart a twist of only a few degrees into
a structure that large, and have it maintain that twist under load and
over time (as opposed to jigged on a bench) is a fairly hard thing to
do correctly.

Also, with the washout, aren't you in effect constantly flying around
with the whole wing at a non-optimal AOA since each part of the wing is
slightly different AOA as you move out on the span?

Since airfoils are a trade off, among other things, of lift, drag, and
range of AOA, wouldn't it be better to extend the stall strip approach
to just having a progressive (or piece wise) airfoil cross section with
a sharper leading edge in-board moving out to a smooth rounded leading
edge near the tips (and ailerons)? So you have a lower drag, reduced
AOA range inboard, and higher drag albiet wider range AOA outboard.
And have no twist in the wing.

Discuss

[Rich S.]

Post by k***@yahoo.com
It seems to me that trying to impart a twist of only a few degrees into
a structure that large, and have it maintain that twist under load and
over time (as opposed to jigged on a bench) is a fairly hard thing to
do correctly.

Not correct. The wing is not built "straight" and then twisted. It is built
with the "twist" jigged in.

Rich S.

[Bill Daniels]

Wing twist, whether geometric or aerodynamic via a change in airfoil
spanwise is designed in. Stall strips are added later if the original
design proves to have unacceptable stall characteristics.

Stall strips hurt performance and should be avoided if at all possible. You
NEVER see stall strips on a sailplane. Careful selection of outboard wing
sections can produce very sweet stall behavior.

Twist, is usually an aerodynamic benefit across the whole speed range. It
helps maintain an elliptical spanwise distribution of lift.

Bill Daniels

Post by k***@yahoo.com
I've noticed a lot of aircraft are designed to use washout at the tips
to control stall behaviour. The idea as it was explained was that they
wanted the inboard part of the wing to stall before the outboard part
so aileron authority could be maintained a little longer.
I've also seen mention of stall strips being installed inboard to try
to affect the same thing.
It seems to me that trying to impart a twist of only a few degrees into
a structure that large, and have it maintain that twist under load and
over time (as opposed to jigged on a bench) is a fairly hard thing to
do correctly.
Also, with the washout, aren't you in effect constantly flying around
with the whole wing at a non-optimal AOA since each part of the wing is
slightly different AOA as you move out on the span?
Since airfoils are a trade off, among other things, of lift, drag, and
range of AOA, wouldn't it be better to extend the stall strip approach
to just having a progressive (or piece wise) airfoil cross section with
a sharper leading edge in-board moving out to a smooth rounded leading
edge near the tips (and ailerons)? So you have a lower drag, reduced
AOA range inboard, and higher drag albiet wider range AOA outboard.
And have no twist in the wing.
Discuss

[t***@mstay.com]

Bill,
Could you advise a source where one could find info on "aerodynamic"
twist? As I understand it, newer designs like the Lancair Legacy do not
have a geometric twist but use different airfoils and taper to provide
the twist. Thanks
Tom
-------

Post by Bill Daniels
Wing twist, whether geometric or aerodynamic via a change in airfoil
spanwise is designed in. Stall strips are added later if the

original

Post by Bill Daniels
design proves to have unacceptable stall characteristics.
Stall strips hurt performance and should be avoided if at all

possible. You

Post by Bill Daniels
NEVER see stall strips on a sailplane. Careful selection of outboard wing
sections can produce very sweet stall behavior.
Twist, is usually an aerodynamic benefit across the whole speed range. It
helps maintain an elliptical spanwise distribution of lift.
Bill Daniels

Post by k***@yahoo.com
I've noticed a lot of aircraft are designed to use washout at the tips
to control stall behaviour. The idea as it was explained was that they
wanted the inboard part of the wing to stall before the outboard part
so aileron authority could be maintained a little longer.
I've also seen mention of stall strips being installed inboard to try
to affect the same thing.
It seems to me that trying to impart a twist of only a few degrees into
a structure that large, and have it maintain that twist under load and
over time (as opposed to jigged on a bench) is a fairly hard thing to
do correctly.
Also, with the washout, aren't you in effect constantly flying around
with the whole wing at a non-optimal AOA since each part of the wing is
slightly different AOA as you move out on the span?
Since airfoils are a trade off, among other things, of lift, drag, and
range of AOA, wouldn't it be better to extend the stall strip approach
to just having a progressive (or piece wise) airfoil cross section with
a sharper leading edge in-board moving out to a smooth rounded leading
edge near the tips (and ailerons)? So you have a lower drag, reduced
AOA range inboard, and higher drag albiet wider range AOA outboard.
And have no twist in the wing.
Discuss

[k***@yahoo.com]

Tom,

You're the one guy that's offered information that supported my
hypothesis. Having an actual twist seems like the last thing you'd
want to do on a "go fast" airplane like the Lancair.

Having the taper and different airfoils is a way of affecting stall
behaviour rather that providing an actual twist which wasn't an end in
itself, simply a method used in the past to achieve an end (stall
performance).

[Morgans]

Post by k***@yahoo.com
I've noticed a lot of aircraft are designed to use washout at the tips
to control stall behaviour. The idea as it was explained was that they
wanted the inboard part of the wing to stall before the outboard part
so aileron authority could be maintained a little longer.
I've also seen mention of stall strips being installed inboard to try
to affect the same thing.

Constant cord (Hershey Bar) wings need no twist, or stall strips, as they
stall naturally on the inboard section, with the tips remaining flying to
the end. They are not as efficient at high speeds as elliptical or tapered
wings, but that is seldom the mission of planes that have constant cord
wings.

[Kyle Boatright]

Post by Morgans

Post by k***@yahoo.com
I've noticed a lot of aircraft are designed to use washout at the tips
to control stall behaviour. The idea as it was explained was that they
wanted the inboard part of the wing to stall before the outboard part
so aileron authority could be maintained a little longer.
I've also seen mention of stall strips being installed inboard to try
to affect the same thing.

Constant cord (Hershey Bar) wings need no twist, or stall strips, as they
stall naturally on the inboard section, with the tips remaining flying to
the end. They are not as efficient at high speeds as elliptical or tapered
wings, but that is seldom the mission of planes that have constant cord
wings.
--
Jim in NC

This may be a good generalization, but I can think of at least two
exceptions. The Grumman AA-1 and the Piper Tomahawk. I've never paid much
attention to the Grumman AA-5, but I wouldn't be surprised to see 'em there
either.

KB

[Morgans]

Post by Kyle Boatright
This may be a good generalization, but I can think of at least two
exceptions. The Grumman AA-1 and the Piper Tomahawk. I've never paid much
attention to the Grumman AA-5, but I wouldn't be surprised to see 'em there
either.
KB

An exception to what? Surprised to see what, where? You gotta incude more
hints, unless you want to play 20 questions! :-)

[Rich S.]

Post by Morgans
An exception to what?

My guess would be your statement that "They (constant chord wings) are not
as efficient at high speeds as elliptical or tapered wings, but that is
seldom the mission of planes that have constant cord wings".

Surprised to see what, where?

Post by Morgans

Post by k***@yahoo.com
I've also seen mention of stall strips being installed inboard to try
to affect the same thing.

Constant cord (Hershey Bar) wings need no twist, or stall strips, as they
stall naturally on the inboard section. . .

But he is a bit obtuse with his referents. :-)

Rich S.

[Kyle Boatright]

Sorry about that. I'm gonna blame nasty sinus infection combined with a
mixture of meds.

My follow-up was directed at JSMorgan's comments on hershey bar wings and
stall strips:

"Constant cord (Hershey Bar) wings need no twist, or stall strips, as they
stall naturally on the inboard section"

Like I was trying to say last night, the AA-1 and Tomahawk both have hershey
bar wings and stall strips.

KB

Post by Morgans

Post by Kyle Boatright
This may be a good generalization, but I can think of at least two
exceptions. The Grumman AA-1 and the Piper Tomahawk. I've never paid

much

Post by Kyle Boatright
attention to the Grumman AA-5, but I wouldn't be surprised to see 'em

there

Post by Kyle Boatright
either.
KB

An exception to what? Surprised to see what, where? You gotta incude more
hints, unless you want to play 20 questions! :-)
--
Jim in NC

[D***@yahoo.com]

Stall strips are used to fix a design shortcoming. No engineer
wants to design a wing that stalls sooner than absolutely necessary,
but some wings didn't behave as predicted and the stall strip was meant
to induce stall on the inboard wing areas and get the nose to drop
before the ailerons lost authority. The Tomahawk has a reputation for
some nasty stall/spin behavior, and I imagine the stall strips were
meant to alleviate it somewhat. The Bonanza has them, too. With newer
computer-generated airflow modelling it's easier to spot deficiencies
before the wing is built.

[k***@yahoo.com]

Sure you don't want the wing to stall before absolutely necessary, but
that is in effect what is done with having washout- making the inboard
section of the wing stall before it absolutely had to. They felt it
was preferable to do that so at the artificially early stall you'd
still have aileron control.

[Ernest Christley]

Post by k***@yahoo.com
Sure you don't want the wing to stall before absolutely necessary, but
that is in effect what is done with having washout- making the inboard
section of the wing stall before it absolutely had to. They felt it
was preferable to do that so at the artificially early stall you'd
still have aileron control.

Not exactly accurate. It more like, you know the plane is going to
stall at some point, but you'd like the pilot to know about it before it
happens. The twist lets the lift drop out slowly as the wing begins to
buffet. Before the spin happens, it is hoped that the pilot will have
awakened and lowered the nose a little.

[Frank van der Hulst]

Post by k***@yahoo.com
Sure you don't want the wing to stall before absolutely necessary, but
that is in effect what is done with having washout- making the inboard
section of the wing stall before it absolutely had to. They felt it
was preferable to do that so at the artificially early stall you'd
still have aileron control.

Yeah -- to put it another way: Putting down an aileron effectively
raises the angle of attack of the outboard part of the wing. So, if you
are near the stall, aileron movement causes the outboard part of the
up-going wing to stall, dropping that wing.

A bit of washout will cure this bad behaviour by having both wings stall
at about the same time.

Frank

[Peter Dohm]

They are also used to generate turbulence (buffet) to wake up the pilot.
In the case of the Tomahawk, they do so with a vengeance and a glance
back at the tail (which is doing quite a dance) will scare you s**tless!

Post by D***@yahoo.com
Stall strips are used to fix a design shortcoming. No engineer
wants to design a wing that stalls sooner than absolutely necessary,
but some wings didn't behave as predicted and the stall strip was meant
to induce stall on the inboard wing areas and get the nose to drop
before the ailerons lost authority. The Tomahawk has a reputation for
some nasty stall/spin behavior, and I imagine the stall strips were
meant to alleviate it somewhat. The Bonanza has them, too. With newer
computer-generated airflow modelling it's easier to spot deficiencies
before the wing is built.

[Roger]

Post by D***@yahoo.com
Stall strips are used to fix a design shortcoming. No engineer
wants to design a wing that stalls sooner than absolutely necessary,
but some wings didn't behave as predicted and the stall strip was meant
to induce stall on the inboard wing areas and get the nose to drop
before the ailerons lost authority. The Tomahawk has a reputation for
some nasty stall/spin behavior, and I imagine the stall strips were
meant to alleviate it somewhat. The Bonanza has them, too. With newer
computer-generated airflow modelling it's easier to spot deficiencies
before the wing is built.

The Bo has both stall strips and wash out, BUT in a stall it is a
"rudder only" airplane.

I see references made to the nose drop. Many aircraft can be held in
a stall without the nose falling. It can be done in the Deb/Bo and it
can be done in a Cherokee with the Hershey bar wing.

HOWEVER there is a marked difference in the way they behave in the
stall. You can hold the Cherokee in a stall and carefully make turns
with the ailerons remaining effective. To say that does not happen in
the Bo would be an understatement.

Holding the Deb/Bo in a stall is like standing on a tight rope that's
not very tight. It's a balancing act done with the rudder and the
ailerons are kept neutral. If there is a general use airplane that
enforces "don't use the ailerons in a stall", it has to be the Bo or
at least the 33s. Forget and use the ailerons and you will get a
chance to put that unusual attitude recovery practice to use.

With practice (and open cowl flaps) you can wobble around in a stall
for quite a while. In a departure stall you can hold a *relatively*
slow rate of descent at full power. Mine does not like partial power
and seems to be a bit more unruly than it is with full, or climb
power.

It is at its nastiest with gear and flaps out. Just stay ahead of the
airplane and it's very predictable even in stalls.

I was doing some checking the other day and found the Deb has a lower
wing loading than a Cherokee 180 and just about half that of a Glasair
III.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

[Morgans]

Post by Roger
I was doing some checking the other day and found the Deb has a lower
wing loading than a Cherokee 180 and just about half that of a Glasair
III.
Roger Halstead

I'm not surprised at that, with the Glasair. Fast glass =high loading. I
am surprised at the 180. Less, but close?

[Roger]

On Thu, 24 Feb 2005 22:36:20 -0500, "Morgans"

Post by Morgans

Post by Roger
I was doing some checking the other day and found the Deb has a lower
wing loading than a Cherokee 180 and just about half that of a Glasair
III.
Roger Halstead

I'm not surprised at that, with the Glasair. Fast glass =high loading. I
am surprised at the 180. Less, but close?

Very close

The Deb is 16.3, and Arrow is 17 and I'm trying to remember the 180 is
slightly less than the Arrow. The G-III is just under 30. (29
something plus change)

The thing is, you can come in very steep (calculate speed for weight)
with just enough power for energy to flare, plant the mains, lower the
nose, get on the brakes, and haul back on the yoke and that sucker
will surprise you with a very short landing and extremely short roll
out.

Stall with only me, half fuel, gear down and full flaps is only 55
MPH. (That is STEEP!)
Going the other direction with that wing loading and 260HP it'll hit
pattern altitude at, or just past the end of the 3800 foot runway.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

[Morgans]

Post by Kyle Boatright
Like I was trying to say last night, the AA-1 and Tomahawk both have hershey
bar wings and stall strips.
KB

The AA-1 had them more to make the high speed stall more noticeable, as I
recall reading , somewhere.

The AA-1 was hot little number, for that HP, and people changing to it from
slower designs could have hardly ever have produced a real mean high speed
stall in their earlier planes, as most other designs of that HP and period
were close to 50% slower.

The stall strips were there to get the pilot's attention, earlier, before
they got into trouble.

Or so I recall reading.

Tomahawks just were nasty to handle in a stall, because of the T-tail way
out of the prop blast, and they need to stall earlier to keep elevator
control? I'm guessing about that one, just from what I have heard.

[Bill Daniels]

"Morgans" <***@chJUarNKer.net> wrote in message news:3qNSd.5262$***@fe04.lga...
snip>

Post by Morgans
Tomahawks just were nasty to handle in a stall, because of the T-tail way
out of the prop blast, and they need to stall earlier to keep elevator
control? I'm guessing about that one, just from what I have heard.
--
Jim in NC

I recall the following story from the early 1970's.

It seems that the #2 American light aircraft manufacturer wanted to compete
with the Cezzna 150 so they built the little Axe prototype with a clean wing
using a nifty new NASA wing section and then asked some CFI's to fly it.
The CFI's said, "Nice little airplane - good performance and very
forgiving." "But, we think a trainer should spin more easily."

So, #2 modified their prototype with stall strips on the OUTBOARD wing
leading edge and asked the CFI's to fly it again. They said, "Man, will
that thing spin - nice trainer".

So, #2 laid off it's design team and built a bunch of Axes. However,
reports started coming in almost immediately of smoking craters as CFI's and
their students spun them in.

#2 needed a quick fix so, in the tradition of American Business Management,
it hired some consultants. The consultants looked in their "How to Fix an
Airplane" comic book for the section on "Bad Stall Behavior". The comic
book said, "Add stall strips to the INBOARD wing leading edge."

There was nothing in the comic book saying, "Remove outboard stall strips."

That's why the Axe has both inboard AND outboard stall strips - and why it
flies like an anvil.

Bill Daniels

[Dude]

Post by Morgans
Tomahawks just were nasty to handle in a stall, because of the T-tail way
out of the prop blast, and they need to stall earlier to keep elevator
control? I'm guessing about that one, just from what I have heard.
--
Jim in NC

Gotta dispel this myth. As the former owner of a T-tail airplane, I can
assure you that the traumahawk's troubles were not merely the result of a
T-tail. The overall design just was not that good.

T-tail vs. Cruciform is just like high vs. low wing.

Piper wanted a T-tail because they thought it would sell more planes. Had
they wanted a high wing I suspect at the time they would have done just as
poorly. You can't just move the horizontal stab and attach it differently
any more than you can do so with the wings. They did, and it didn't work
well.

[Morgans]

Post by Dude
Gotta dispel this myth. As the former owner of a T-tail airplane, I can
assure you that the traumahawk's troubles were not merely the result of a
T-tail. The overall design just was not that good.

What was wrong with the design? Of course, this is all your opinion. <g>

[Kyle Boatright]

Post by Morgans

Post by Dude
Gotta dispel this myth. As the former owner of a T-tail airplane, I can
assure you that the traumahawk's troubles were not merely the result of a
T-tail. The overall design just was not that good.

What was wrong with the design? Of course, this is all your opinion. <g>
--
Jim in NC

I owned a Tomahawk for 5 or 6 years. A great little airplane. Compared to
the Cessna two seaters, it has more interior room, better visibiltiy, and
equal cruise performance. The stall speed is 10 mph faster, and the
airplane can/will drop a wing if you stall it (but I've done that trick in a
C-152 as well). FBO gossip would have you believe that dozens of Tomahawks
have spun in due to unrecoverable spins during training, wheras a review of
the NTSB reports doesn't show this at all. Instead, it shows that quite a
few have gone down due to low altitude stalls and/or spins. Anyone who
stalls an airplane in the pattern is looking for trouble, and the Tomahawk
isn't as forgiving in that regime as a C-152.

Could Piper have done a better job? Certainly. They chose a high performance
airfoil in an application where it offered more disadvantages than
advantages. Beyond that, they didn't design the tail structure properly,
which led to a series of AD's. Last time I checked, no Tomahawks had been
lost due to structural failures, which is the other FBO rumor about the
Tomahawk - "the tail will come off"...

KB

[Mark Smith]

Post by Kyle Boatright

Post by Morgans

Post by Dude
Gotta dispel this myth. As the former owner of a T-tail airplane, I can
assure you that the traumahawk's troubles were not merely the result of a
T-tail. The overall design just was not that good.

What was wrong with the design? Of course, this is all your opinion. <g>
--
Jim in NC

I owned a Tomahawk for 5 or 6 years. A great little airplane. Compared to
the Cessna two seaters, it has more interior room, better visibiltiy, and
equal cruise performance. The stall speed is 10 mph faster, and the
airplane can/will drop a wing if you stall it (but I've done that trick in a
C-152 as well). FBO gossip would have you believe that dozens of Tomahawks
have spun in due to unrecoverable spins during training, wheras a review of
the NTSB reports doesn't show this at all. Instead, it shows that quite a
few have gone down due to low altitude stalls and/or spins. Anyone who
stalls an airplane in the pattern is looking for trouble, and the Tomahawk
isn't as forgiving in that regime as a C-152.
Could Piper have done a better job? Certainly. They chose a high performance
airfoil in an application where it offered more disadvantages than
advantages. Beyond that, they didn't design the tail structure properly,
which led to a series of AD's. Last time I checked, no Tomahawks had been
lost due to structural failures, which is the other FBO rumor about the
Tomahawk - "the tail will come off"...
KB

So are you saying it is a really great plane,

or a real piece of shit ?


I am glad to read that it on;y stall/spins/kills folks in the pattern
and never during training.

I'll know just when to sell it !

[Kyle Boatright]

"

Post by Mark Smith

Post by Kyle Boatright
I owned a Tomahawk for 5 or 6 years. A great little airplane. Compared to
the Cessna two seaters, it has more interior room, better visibiltiy, and
equal cruise performance. The stall speed is 10 mph faster, and the
airplane can/will drop a wing if you stall it (but I've done that trick in a
C-152 as well). FBO gossip would have you believe that dozens of
Tomahawks
have spun in due to unrecoverable spins during training, wheras a review of
the NTSB reports doesn't show this at all. Instead, it shows that quite a
few have gone down due to low altitude stalls and/or spins. Anyone who
stalls an airplane in the pattern is looking for trouble, and the Tomahawk
isn't as forgiving in that regime as a C-152.
Could Piper have done a better job? Certainly. They chose a high performance
airfoil in an application where it offered more disadvantages than
advantages. Beyond that, they didn't design the tail structure properly,
which led to a series of AD's. Last time I checked, no Tomahawks had been
lost due to structural failures, which is the other FBO rumor about the
Tomahawk - "the tail will come off"...
KB

So are you saying it is a really great plane,
or a real piece of shit ?
I am glad to read that it on;y stall/spins/kills folks in the pattern
and never during training.
I'll know just when to sell it !
--
Mark Smith
Tri-State Kite Sales
1121 N Locust St
Mt Vernon, IN 47620
1-812-838-6351

The point is that pattern altitude (or less) is a bad place to stall an
airplane. Stall on the base to final turn in all but the most forgiving GA
aircraft and your chances of meeting your maker are pretty good.

KB

[Roger]

On Mon, 21 Feb 2005 17:42:36 -0500, "Morgans"

Post by Morgans

Post by k***@yahoo.com
I've noticed a lot of aircraft are designed to use washout at the tips
to control stall behaviour. The idea as it was explained was that they
wanted the inboard part of the wing to stall before the outboard part
so aileron authority could be maintained a little longer.
I've also seen mention of stall strips being installed inboard to try
to affect the same thing.

Constant cord (Hershey Bar) wings need no twist, or stall strips, as they
stall naturally on the inboard section, with the tips remaining flying to
the end. They are not as efficient at high speeds as elliptical or tapered
wings, but that is seldom the mission of planes that have constant cord
wings.

The old "Hershey Bar Wing" Cherokees are the only planes I've flow
that I could put into a stall, keep it in the stall, and still make
turns using the ailerons. Many airplanes don't like that and in
particular the Bo series of planes are likely to roll over with which
ever wing you try to raise going down instead. It's amazing how fast
they can put the greasy side up.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

[Orval Fairbairn]

Post by Roger
On Mon, 21 Feb 2005 17:42:36 -0500, "Morgans"

Post by Morgans

Post by k***@yahoo.com
I've noticed a lot of aircraft are designed to use washout at the tips
to control stall behaviour. The idea as it was explained was that they
wanted the inboard part of the wing to stall before the outboard part
so aileron authority could be maintained a little longer.
I've also seen mention of stall strips being installed inboard to try
to affect the same thing.

Constant cord (Hershey Bar) wings need no twist, or stall strips, as they
stall naturally on the inboard section, with the tips remaining flying to
the end. They are not as efficient at high speeds as elliptical or tapered
wings, but that is seldom the mission of planes that have constant cord
wings.

The old "Hershey Bar Wing" Cherokees are the only planes I've flow
that I could put into a stall, keep it in the stall, and still make
turns using the ailerons. Many airplanes don't like that and in
particular the Bo series of planes are likely to roll over with which
ever wing you try to raise going down instead. It's amazing how fast
they can put the greasy side up.
Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

The old Meyers 200 was another plane that you could hold in a stall and
rock the wings with the ailerons without falling off into a spin. It
also had about 3 deg of wing twist.

[Jan Carlsson]

Some aeroplanes have stall strips just to give stall warning, by make the
h-tail vibrate from the turbulence.

some Hershey-bar wings have twist to improve its handling.

most all taper wing have some washout in form of twist or aerodynamically or
a combination of the two.

aerodynamic washout can be achieved by using an airfoil at the tip with more
camber, or more nose camber (drop nose)

Messersmith was probably one of the first to use a combination of twist and
a more cambered tip airfoil, it is made so the zero-lift line at tip have a
small amount of twist compered to the root airfoils zero-lift line, the cord
line have then a larger amount of twist. At high speed the tip will not
produce negative lift due to the small difference in zero-lift line.

Jan Carlsson
www.jcpropellerdesign.com