Question - rudder flutter ?

[Bravo Two Zero]

What is rudder flutter ?

[Bertie the Bunyip[_19_]]

"Bravo Two Zero" > wrote in news:EyZbj.1217$Gr4.669
@newsfe08.phx:

> What is rudder flutter ?
>
>
>

A bit like the way a flag whips in a high wind. Any control surface can
flutter if the supporting surface is flexible enough to allow a
complimentary cyclic oscillation of the two surfaces (control and
stabilising surfaces).
Here's how it works. The control surface is displaced, loading up the
adjacent stabilising surface and bending it over to one side (the fin
in this case, but it can be the stab or the wing just as easily) The fin
has now suddenly been pushed to one side under tension and may now
spring back in the other direction carrying the hinged edge of the
rudder with it. the trailing edge of the rudder, however, will be left
behind in this move, deflecting and thereby making a control input that
contributes considerable force in the direction the rudder is now
moving. ( I know, I know, a pic here would help, but bear with me) the
fin is now stretched out in the other direction and ready to spring back
the other way repeating the cycle.
If the rudder is balanced on the hinge line, it will be far less likely
to support this cycle. The other way you can stem it is to make the stab
fin or wing very rigid and this is why biplanes can have as high a
redline as , say a Mooney might though the bipe might have no balance
area at all and the Mooney would. All the surfaces are too rigid to
allow the cycle to start.
You would think that a greater load on the surface, i.e, "G". would tend
to dampen the action, but the opposite is the case.
Flutter will appear at a lower speed if the surface has an aerodynamic
load on it.
Aerobatics are the most common arena for flutter, but poor maintenance
can also bring it on. A lot of high performance light planes have been
lost simply because they have been repainted without rebalancing the
surface, or the balance material has come loose or lost in a rebuild.
Mass balance is typically a bit of lead buried in a balance horn or some
other bit of the control surface ahead of the hinge line.
Aerodynamic balance can also be employed to help in this and that's
often where the mass balance is housed as well.
Large aircraft often use depleted uranium for the mass balance, BTW!




Bertie

[WingFlaps[_2_]]

On Dec 25, 4:18 pm, Bertie the Bunyip > wrote:
> "Bravo Two Zero" > wrote in news:EyZbj.1217$Gr4.669
> @newsfe08.phx:
>
> > What is rudder flutter ?
>
> A bit like the way a flag whips in a high wind. Any control surface can
> flutter if the supporting surface is flexible enough to allow a
> complimentary cyclic oscillation of the two surfaces (control and
> stabilising surfaces).
> Here's how it works. The control surface is displaced, loading up the
> adjacent stabilising surface and bending it over to one side (the fin
> in this case, but it can be the stab or the wing just as easily) The fin
> has now suddenly been pushed to one side under tension and may now
> spring back in the other direction carrying the hinged edge of the
> rudder with it. the trailing edge of the rudder, however, will be left
> behind in this move, deflecting and thereby making a control input that
> contributes considerable force in the direction the rudder is now
> moving. ( I know, I know, a pic here would help, but bear with me) the
> fin is now stretched out in the other direction and ready to spring back
> the other way repeating the cycle.
> If the rudder is balanced on the hinge line, it will be far less likely
> to support this cycle. The other way you can stem it is to make the stab
> fin or wing very rigid and this is why biplanes can have as high a
> redline as , say a Mooney might though the bipe might have no balance
> area at all and the Mooney would. All the surfaces are too rigid to
> allow the cycle to start.
> You would think that a greater load on the surface, i.e, "G". would tend
> to dampen the action, but the opposite is the case.
> Flutter will appear at a lower speed if the surface has an aerodynamic
> load on it.
> Aerobatics are the most common arena for flutter, but poor maintenance
> can also bring it on. A lot of high performance light planes have been
> lost simply because they have been repainted without rebalancing the
> surface, or the balance material has come loose or lost in a rebuild.
> Mass balance is typically a bit of lead buried in a balance horn or some
> other bit of the control surface ahead of the hinge line.
> Aerodynamic balance can also be employed to help in this and that's
> often where the mass balance is housed as well.
> Large aircraft often use depleted uranium for the mass balance, BTW!
>
> Bertie

To add to Bertie

The bottom line is that If the COG of the surface is behind it's
center of lift flutter is promoted. That's why most control surfaces
add weights (depleted uranium!?) to bring the COG forward. On the
preflight you check that that balance weights are there and fixed.
Flutter will destroy the surface, structure and it's hinges pretty
quickly.

Cheers

[Bertie the Bunyip[_19_]]

WingFlaps > wrote in news:797747ee-e7ec-4c72-b61b-
:

>
> The bottom line is that If the COG of the surface is behind it's
> center of lift flutter is promoted. That's why most control surfaces
> add weights (depleted uranium!?) to bring the COG forward. On the
> preflight you check that that balance weights are there and fixed.
> Flutter will destroy the surface, structure and it's hinges pretty
> quickly.
Actually, that's not quite correct. the CG of the surface has to be at the
hinge line, not it's Cl. to eliminate this tendency. It's down to the
rididity of the hinge in space, though. The less rigid the greater the need
for balancing. Most wings and stab surfaces are quite flexible, though, so
at least some balance, if not 100% (which would put it at the hinge line)
is reguired for most airplanes.


I saw a video of a twin Comanche on You tuvbe flutterign badly during
tests, but I can't find it now. The other ones there don't illustrate it
very well excepet maybe this one. http://www.youtube.com/watch?v=
8D7YCCLGu5Y
No control surface, but it's the flexibility of the wing that's causing the
problem. It's increasing in amplitude because each subsequent oscillation
is further and when it moves further it increases alpha which in turn
imparts more energy to the next oscillation..


Bertie

[WingFlaps[_2_]]

On Dec 26, 12:15 am, Bertie the Bunyip > wrote:
> WingFlaps > wrote in news:797747ee-e7ec-4c72-b61b-
> :
>
>
>
> > The bottom line is that If the COG of the surface is behind it's
> > center of lift flutter is promoted. That's why most control surfaces
> > add weights (depleted uranium!?) to bring the COG forward. On the
> > preflight you check that that balance weights are there and fixed.
> > Flutter will destroy the surface, structure and it's hinges pretty
> > quickly.
>
> Actually, that's not quite correct. the CG of the surface has to be at the
> hinge line, not it's Cl. to eliminate this tendency. It's down to the
> rididity of the hinge in space, though. The less rigid the greater the need
> for balancing. Most wings and stab surfaces are quite flexible, though, so
> at least some balance, if not 100% (which would put it at the hinge line)
> is reguired for most airplanes.
>

Err, I didn's say the Cl was at the hinge line (rather that COG must
be forward of control surface lift). But I agree, if the COG _can_ be
put at the the hinge line then not just control surface flutter is
reduced but also flying surface flutter (in this case fin + rudder).
The trouble with the lightt structures in a plane is that balancing
one end (e.g. with a leaded horn) may lead to tortional problems...

Cheers

[WingFlaps[_2_]]

On Dec 26, 12:15 am, Bertie the Bunyip > wrote:

>
> I saw a video of a twin Comanche on You tuvbe flutterign badly during
> tests, but I can't find it now. The other ones there don't illustrate it
> very well excepet maybe this one.http://www.youtube.com/watch?v=
> 8D7YCCLGu5Y
> No control surface, but it's the flexibility of the wing that's causing the
> problem. It's increasing in amplitude because each subsequent oscillation
> is further and when it moves further it increases alpha which in turn
> imparts more energy to the next oscillation..

That sounds like divergence (not flutter)? Divergence is due to the
flexibility of the structure and a great example is Tacoma narrows?

Cheers

That

[Bertie the Bunyip[_19_]]

WingFlaps > wrote in
:

> On Dec 26, 12:15 am, Bertie the Bunyip > wrote:
>> WingFlaps > wrote in
>> news:797747ee-e7ec-4c72-b61b-
>> :
>>
>>
>>
>> > The bottom line is that If the COG of the surface is behind it's
>> > center of lift flutter is promoted. That's why most control
>> > surfaces add weights (depleted uranium!?) to bring the COG forward.
>> > On the preflight you check that that balance weights are there and
>> > fixed. Flutter will destroy the surface, structure and it's hinges
>> > pretty quickly.
>>
>> Actually, that's not quite correct. the CG of the surface has to be
>> at the hinge line, not it's Cl. to eliminate this tendency. It's down
>> to the rididity of the hinge in space, though. The less rigid the
>> greater the need for balancing. Most wings and stab surfaces are
>> quite flexible, though, so at least some balance, if not 100% (which
>> would put it at the hinge line) is reguired for most airplanes.
>>
>
> Err, I didn's say the Cl was at the hinge line (rather that COG must
> be forward of control surface lift).


I know. I understood what you said, but the Cl of the surface is
irrelevant to flutter.


But I agree, if the COG _can_ be
> put at the the hinge line then not just control surface flutter is
> reduced but also flying surface flutter (in this case fin + rudder).

They're th esame thing, really. Although you can have eiter, they're
caused by the same situation, the surface as a whole, whether or not it
has a seperate flying surface or not, is producing and flexing the
surface.
The control surface element is caused by the rudder or whatever, lagging
behind the moving fin due to inertia. This causes displacement of the
rudder and creates a rudder input which provokes the movement of the fin
even further. the combined inertia stretches the elastic fin and when it
gets as far as it;'s going to go in that direction, the elastic property
of the construction material flips it back the other way, leaving the
rudder behind and causing another rudder input in the opposite direction
and so on, increasing in amplitude until something fails, be it the
hinge, the spar, or whatever reahes it's limit first. Usually it's the
spar.

> The trouble with the lightt structures in a plane is that balancing
> one end (e.g. with a leaded horn) may lead to tortional problems..

Huh?
Torsional flutter is kinda outside the scope of this explanation, but
the amount required if you put it at the tip would be lower anyway if
you're not shooting for 100%, so that's why it is placed at the end if
that's the solution required. There are a few types where massive lumps
are mounted at the outboard ends of the ailerons. Others, like Cessnas,
just have loooong strips inside the hinge gap.

It's done all the time, but it doesn;t have to be at one end and it
doesn't have to be a horn. It also doesn't have to be a 100% balance if
the performance doesn't neccesitate it or if the stab or wing is rigid
enough for flutter not to be an issue within the speed envelope.
But for anythng that goes very fast, you have to have 100% balancing,
which means it's statically balanced at the hinge line.


Bertie

[[email protected]]

> The other way you can stem it is to make the stab
> fin or wing very rigid and this is why biplanes can have as high a
> redline as , say a Mooney might though the bipe might have no balance
> area at all and the Mooney would.

Is this because of the welded 4130 tube structure?

[Bertie the Bunyip[_19_]]

WingFlaps > wrote in
:

> On Dec 26, 12:15 am, Bertie the Bunyip > wrote:
>
>>
>> I saw a video of a twin Comanche on You tuvbe flutterign badly during
>> tests, but I can't find it now. The other ones there don't illustrate
>> it very well excepet maybe this one.http://www.youtube.com/watch?v=
>> 8D7YCCLGu5Y
>> No control surface, but it's the flexibility of the wing that's
>> causing the problem. It's increasing in amplitude because each
>> subsequent oscillation is further and when it moves further it
>> increases alpha which in turn imparts more energy to the next
>> oscillation..
>
> That sounds like divergence (not flutter)? Divergence is due to the
> flexibility of the structure and a great example is Tacoma narrows?
>


hmm, true.

Well, flutter is also down to flexibility. All kinds of flutter in all it's
incarnations.
So I suppose it could be said that flutter is a species of divergence.
Dunno, I'm not an engineer! What I've given is the dumbed down pilot
version of flutter.


Bertie

[Bertie the Bunyip[_19_]]

wrote in news:d6ec528a-01a1-4a71-a603-
:

>> The other way you can stem it is to make the stab
>> fin or wing very rigid and this is why biplanes can have as high a
>> redline as , say a Mooney might though the bipe might have no balance
>> area at all and the Mooney would.
>
> Is this because of the welded 4130 tube structure?
>

No, the rigging. The wings on a bipe won't budge at all because of the
flying wires. Same for the stab. 4130 will flex really easily by itself.
You can bend it by hand!
But even the tail surfaces on those airplanes are braced at about half span
so they don't flex significantly. A cantilever aluminum or even a wood
structure will flex quite a lot so that must be taken into consideration if
you want any kind of reasonable redline.
That kind of exhausts my knowledge of the subject, but there are some guys
over in rec.aviation.homebuilt, amongst other places, that know this stuff
backwards and forwards.
Anthony also probably knows it just backwards



Bertie

[WingFlaps[_2_]]

On Dec 26, 5:31 am, Bertie the Bunyip > wrote:

> It's done all the time, but it doesn;t have to be at one end and it
> doesn't have to be a horn. It also doesn't have to be a 100% balance if
> the performance doesn't neccesitate it or if the stab or wing is rigid
> enough for flutter not to be an issue within the speed envelope.
> But for anythng that goes very fast, you have to have 100% balancing,
> which means it's statically balanced at the hinge line.
>

Even more than 100% is needed in some common planes (e.g. the
Bonanza). In this case a wing roll will be dampened automatically (I
think) -I'd guess it makes the plane feel more docile, but perhaps
you know this plane and can comment. But I disagree with you about one
point, the center of lift of the control surface is still important. I
think this is because the control linkages aren't stiff enough to stop
a control surface flutter. (I am keeping to the question of control
surface flutter and trying to avoid the coupling in of the flying
surface the control is attached to.)
I think you would agree that if the Cl of the surface were ahead of
it's COG control surface flutter would be guaranteed (no linkages
would be stiff enough to control it)? I believe that this mode may be
excited by the disturbed air flowing through the gap between control
surface and wing which slightly reduces the surface lift on one side
which then couples into the potential for the flutter. It would be
felt as a vibration in the stick whereas a wing flutter _might_ not be
felt through the stick at all (esp. if the control surface is 100%
balanced!!)

Nice to have a bit of flying/tech discussion instead of troll lures.

Cheers

leads to . I'll agree that normally the Cl will be behind the COG for
a typical triangular section control surface but if a dynamically
balanced design is sought, the Cl moves much closer to the hinge line
and then the COG may not be far enough forward. I'd suspect this might
have been a big problem with some early WW1 type rudders that looked
to be highly balanced.

Cheers

[WingFlaps[_2_]]

On Dec 26, 5:44 am, Bertie the Bunyip > wrote:

> Anthony also probably knows it just backwards

Does his sim show flutter beyond Vne? I wonder how that effect is
conveyed to the 'pilot' .

Cheers

[Bertie the Bunyip[_19_]]

WingFlaps > wrote in news:7896a421-7658-44d1-
:

> On Dec 26, 5:31 am, Bertie the Bunyip > wrote:
>
>> It's done all the time, but it doesn;t have to be at one end and it
>> doesn't have to be a horn. It also doesn't have to be a 100% balance
if
>> the performance doesn't neccesitate it or if the stab or wing is
rigid
>> enough for flutter not to be an issue within the speed envelope.
>> But for anythng that goes very fast, you have to have 100% balancing,
>> which means it's statically balanced at the hinge line.
>>
>
> Even more than 100% is needed in some common planes (e.g. the
> Bonanza). In this case a wing roll will be dampened automatically (I
> think) -I'd guess it makes the plane feel more docile, but perhaps
> you know this plane and can comment. But I disagree with you about one
> point, the center of lift of the control surface is still important. I
> think this is because the control linkages aren't stiff enough to stop
> a control surface flutter. (I am keeping to the question of control
> surface flutter and trying to avoid the coupling in of the flying
> surface the control is attached to.)
> I think you would agree that if the Cl of the surface were ahead of
> it's COG control surface flutter would be guaranteed (no linkages
> would be stiff enough to control it)? I believe that this mode may be
> excited by the disturbed air flowing through the gap between control
> surface and wing which slightly reduces the surface lift on one side
> which then couples into the potential for the flutter. It would be
> felt as a vibration in the stick whereas a wing flutter _might_ not be
> felt through the stick at all (esp. if the control surface is 100%
> balanced!!)
>
> Nice to have a bit of flying/tech discussion instead of troll lures.

Anthony must be out begging. I was bored.
>
> Cheers
>
> leads to . I'll agree that normally the Cl will be behind the COG for
> a typical triangular section control surface but if a dynamically
> balanced design is sought, the Cl moves much closer to the hinge line
> and then the COG may not be far enough forward. I'd suspect this might
> have been a big problem with some early WW1 type rudders that looked
> to be highly balanced.
>

Don;t think what you're saying about the Cl and the GG realationship of
the surface is correct, but I don't know for sure. The way most control
surfaces are constructed would pretty much gauruntee that that is the
case ( skinny at the back) but it's the wing or stab that is th emore
important ingredient there anyway.
Big flexible surfaces can flutter all by themselves as shown in that
clip of the A6 I posted and that might be what you mean about the Cl CG
relationship. In fact that's one of the reasons that a wing mounted
engine is a good idea and why the pods on jet airliners (which have the
structural rigidity of Jel-lo) are mounted out in front. The change in
CG helps dampen the flutter in the same way as mass balance on an
aileron would.


Bertie
>
>

[Bertie the Bunyip[_19_]]

WingFlaps > wrote in news:a27e082e-83e1-4df1-a634-
:

> On Dec 26, 5:44 am, Bertie the Bunyip > wrote:
>
>> Anthony also probably knows it just backwards
>
> Does his sim show flutter beyond Vne? I wonder how that effect is
> conveyed to the 'pilot' .

You could program it as a learning tool, but all it would be.is a lesson,
not an experience.


Sims are programmed to do all sorts of things like that, but it might as
well be a balloon that opens up and says "You're fluttering" as anything
else.


Bertie

[[email protected]]

> to support this cycle. The other way you can stem it is to make the stab
> fin or wing very rigid and this is why biplanes can have as high a
> redline as , say a Mooney might though the bipe might have no balance
> area at all and the Mooney would. All the surfaces are too rigid to
> allow the cycle to start.
> You would think that a greater load on the surface, i.e, "G". would tend
> to dampen the action, but the opposite is the case.
> Flutter will appear at a lower speed if the surface has an aerodynamic
> load on it.


So at a practical level, is it reasonable to say that avoiding a red-
lining of airspeed is sufficient to avoid flutter in small GA
airplanes? Or are there other things to watch out for in normal flight
to avoid flutter? I didn't quite follow the part about flutter at
lower speeds but thanks for the informative post,

[[email protected]]

On Dec 25, 10:44*am, Bertie the Bunyip > wrote:
> wrote in news:d6ec528a-01a1-4a71-a603-
> :
>
> >> The other way you can stem it is to make the stab
> >> fin or wing very rigid and this is why biplanes can have as high a
> >> redline as , say a Mooney might though the bipe might have no balance
> >> area at all and the Mooney would.
>
> > Is this because of the welded 4130 tube structure?
>
> No, the rigging. The wings on a bipe won't budge at all because of the
> flying wires. Same for the stab. 4130 will flex really easily by itself.
> You can bend it by hand!
> But even the tail surfaces on those airplanes are braced at about half span
> so they don't flex significantly. A cantilever aluminum or even a wood
> structure will flex quite a lot so that must be taken into consideration if
> you want any kind of reasonable redline.
> That kind of exhausts my knowledge of the subject, but there are some guys
> over in rec.aviation.homebuilt, amongst other places, that know this stuff
> backwards and forwards.
> Anthony also probably knows it just backwards
>
> Bertie

Ah, bracing. So the vertical stabilizer of a 4130 is internally braced
by cable?

Well, I figure I'm going to order the plans for the AcroSport II, even
if I don't wind up building it as a first aircraft (or ever). $125
ain't exactly expensive. I spend more on wines for dinner every couple
of weeks.

I'll still probably go STOL first, it'll take a lot less time to
build.

The links to the wing flutter and failure were VERY edumacational. Vne
-- respect it with your life.

[george]

On Dec 26, 6:36 am, WingFlaps > wrote:
> On Dec 26, 5:44 am, Bertie the Bunyip > wrote:
>
> > Anthony also probably knows it just backwards
>
> Does his sim show flutter beyond Vne? I wonder how that effect is
> conveyed to the 'pilot' .
>
His Vne is when the monitor falls off the desk

[Bertie the Bunyip[_19_]]

wrote in news:2615a64e-b660-42a1-a2a2-e09e08ff5b94
@i12g2000prf.googlegroups.com:

>
>> to support this cycle. The other way you can stem it is to make the stab
>> fin or wing very rigid and this is why biplanes can have as high a
>> redline as , say a Mooney might though the bipe might have no balance
>> area at all and the Mooney would. All the surfaces are too rigid to
>> allow the cycle to start.
>> You would think that a greater load on the surface, i.e, "G". would tend
>> to dampen the action, but the opposite is the case.
>> Flutter will appear at a lower speed if the surface has an aerodynamic
>> load on it.
>
>
> So at a practical level, is it reasonable to say that avoiding a red-
> lining of airspeed is sufficient to avoid flutter in small GA
> airplanes?

Yeah. If the airplane itself is OK. I can't think of any other reason why
it would start.

Or are there other things to watch out for in normal flight
> to avoid flutter? I didn't quite follow the part about flutter at
> lower speeds but thanks for the informative post,


Relative to where it would start unloaded. IOW if you were overspeeding as
a result of an unusual attitude recovery and you were pulling like hell at
the same time, the flutter would appear at a lower airspeed than it would
if you were just in a dive with the wing loaded at 1 G. Both of these
speeds should still be over red-line.

Bertie

[Bertie the Bunyip[_19_]]

wrote in
:

> On Dec 25, 10:44*am, Bertie the Bunyip > wrote:
>> wrote in news:d6ec528a-01a1-4a71-a603-
>> :
>>
>> >> The other way you can stem it is to make the stab
>> >> fin or wing very rigid and this is why biplanes can have as high a
>> >> redline as , say a Mooney might though the bipe might have no
>> >> balance area at all and the Mooney would.
>>
>> > Is this because of the welded 4130 tube structure?
>>
>> No, the rigging. The wings on a bipe won't budge at all because of
>> the flying wires. Same for the stab. 4130 will flex really easily by
>> itself. You can bend it by hand!
>> But even the tail surfaces on those airplanes are braced at about
>> half spa
> n
>> so they don't flex significantly. A cantilever aluminum or even a
>> wood structure will flex quite a lot so that must be taken into
>> consideration i
> f
>> you want any kind of reasonable redline.
>> That kind of exhausts my knowledge of the subject, but there are some
>> guys
>
>> over in rec.aviation.homebuilt, amongst other places, that know this
>> stuff
>
>> backwards and forwards.
>> Anthony also probably knows it just backwards
>>
>> Bertie
>
> Ah, bracing. So the vertical stabilizer of a 4130 is internally braced
> by cable?

No, I'm talking about airplanes like Cubs or homebuilt bipes with
externally wire braced tails. Having said that, I don't think the
Wittman Tailwind has externally braced tail surfaces and I'm pretty sure
the tail is 4130 tube and God knows it's fast, so I don't know how Steve
Wittman managed that.
>
> Well, I figure I'm going to order the plans for the AcroSport II, even
> if I don't wind up building it as a first aircraft (or ever). $125
> ain't exactly expensive. I spend more on wines for dinner every couple
> of weeks.
>
> I'll still probably go STOL first, it'll take a lot less time to
> build.

What, like a Kitfox?

Bertie

[[email protected]]

On Dec 25, 1:22*pm, george > wrote:
> On Dec 26, 6:36 am, WingFlaps > wrote:> On Dec 26, 5:44 am, Bertie the Bunyip > wrote:
>
> > > Anthony also probably knows it just backwards
>
> > Does his sim show flutter beyond Vne? I wonder how that effect is
> > conveyed to the 'pilot' .
>
> His Vne is when the monitor falls off the desk

Heh, catastrophic failure.

I was goofing around with MSFT a couple of weeks ago. Downloaded a
182RG. It sucked, kinda, cause it was freeware.

Anyway I pushed past Vne. The plane started "shaking" --
uncontrollable oscillations which, I guess, might've led to it coming
apart. But I pulled out of the "dive" before that happened. I've had
the T-38 bust on me by "pulling up" too quickly at high simulated
speed.

[[email protected]]

> What, like a Kitfox?
>

CH701.

There's a guy has his own grass strip just east of Burnet (shows up as
Deiterich on the San Anton sectional), he's got a 701 and I hope to go
out and take a look at it pretty soon. Just need to find the time.

It is very small but it looks quite fun for STOL operations.

Only thing about it is that, even though you only need a short space
to land in, if you do loose your engine there better be a field within
a couple of miles -- glide ratio little better than a piano ...

[Bertie the Bunyip[_19_]]

wrote in news:b417bb1d-52bc-4423-8300-
:

>> What, like a Kitfox?
>>
>
> CH701.
>
> There's a guy has his own grass strip just east of Burnet (shows up as
> Deiterich on the San Anton sectional), he's got a 701 and I hope to go
> out and take a look at it pretty soon. Just need to find the time.
>
> It is very small but it looks quite fun for STOL operations.
>
> Only thing about it is that, even though you only need a short space
> to land in, if you do loose your engine there better be a field within
> a couple of miles -- glide ratio little better than a piano ...
>

You'll get one of those thngs out of anywhere, but if the field is, say,
400 yards or more, you'll get an acrosport in and out of it easily. Even
shorter if ou're sharp.

Bertie

[[email protected]]

> You'll get one of those thngs out of anywhere, but if the field is, say,
> 400 yards or more, you'll get an acrosport in and out of it easily. Even
> shorter if ou're sharp.
>

Suffice to say I'm pretty excited about the AcroSport, it's
performance, and how you can fly it. Plus, it's a fabric covered
biplane. How kick azz is that? Well, very.

It's a longer term project though.

I wonder if you could use a Mazda 13B -- should fit in the weight / hp
range. Not many moving parts to break, either. Hmm. Don't know if
anybody's done aerobatics with a 13B though.

I want to give a shot at plans building the 701. There's a nice set of
videos that show quite a bit of the 701 construction sequence from
those Canadian guys at Can Zac. I might buy some of it as a kit to
save some time though.

I suppose these thoughts are way off topic. To bring it back: I know
of only one Zenith STOL that had structural failure probably due to
flutter as a result of exceeding Vne: somebody dived an 801 at the
ground and apprently ripped the wings off on the way down. NTSB report
says both pilot and passenger had a good bit of THC in their blood ...
only fatalities I know of in the STOL series from Zenith and clearly
pilot caused.

[WingFlaps]

On Dec 26, 6:45 am, Bertie the Bunyip > wrote:
> WingFlaps > wrote in news:7896a421-7658-44d1-
> :
>
>
>
>
>
> > On Dec 26, 5:31 am, Bertie the Bunyip > wrote:
>
> >> It's done all the time, but it doesn;t have to be at one end and it
> >> doesn't have to be a horn. It also doesn't have to be a 100% balance
> if
> >> the performance doesn't neccesitate it or if the stab or wing is
> rigid
> >> enough for flutter not to be an issue within the speed envelope.
> >> But for anythng that goes very fast, you have to have 100% balancing,
> >> which means it's statically balanced at the hinge line.
>
> > Even more than 100% is needed in some common planes (e.g. the
> > Bonanza). In this case a wing roll will be dampened automatically (I
> > think) -I'd guess it makes the plane feel more docile, but perhaps
> > you know this plane and can comment. But I disagree with you about one
> > point, the center of lift of the control surface is still important. I
> > think this is because the control linkages aren't stiff enough to stop
> > a control surface flutter. (I am keeping to the question of control
> > surface flutter and trying to avoid the coupling in of the flying
> > surface the control is attached to.)
> > I think you would agree that if the Cl of the surface were ahead of
> > it's COG control surface flutter would be guaranteed (no linkages
> > would be stiff enough to control it)? I believe that this mode may be
> > excited by the disturbed air flowing through the gap between control
> > surface and wing which slightly reduces the surface lift on one side
> > which then couples into the potential for the flutter. It would be
> > felt as a vibration in the stick whereas a wing flutter _might_ not be
> > felt through the stick at all (esp. if the control surface is 100%
> > balanced!!)
>
> > Nice to have a bit of flying/tech discussion instead of troll lures.
>
> Anthony must be out begging. I was bored.
>
>
>
> > Cheers
>
> > leads to . I'll agree that normally the Cl will be behind the COG for
> > a typical triangular section control surface but if a dynamically
> > balanced design is sought, the Cl moves much closer to the hinge line
> > and then the COG may not be far enough forward. I'd suspect this might
> > have been a big problem with some early WW1 type rudders that looked
> > to be highly balanced.
>
> Don;t think what you're saying about the Cl and the GG realationship of
> the surface is correct, but I don't know for sure. The way most control
> surfaces are constructed would pretty much gauruntee that that is the
> case ( skinny at the back) but it's the wing or stab that is th emore
> important ingredient there anyway.

Yes, I agree that the wing or stab is important -but control surface
flutter (maybe more common in models with loose linkages) is bad too.
Loss of the elevator is probably a terminal failure.

> Big flexible surfaces can flutter all by themselves as shown in that
> clip of the A6 I posted and that might be what you mean about the Cl CG
> relationship.

Yes that's what I'm thinking about.

>In fact that's one of the reasons that a wing mounted
> engine is a good idea and why the pods on jet airliners (which have the
> structural rigidity of Jel-lo) are mounted out in front. The change in
> CG helps dampen the flutter in the same way as mass balance on an
> aileron would.

A good point, I hadn't thought about engine pylons serving that
function.

Cheers

[Stefan]

Bravo Two Zero schrieb:

> What is rudder flutter ?

This is rudder flutter. (Actually, it's aileron flutter, but the
principle is the same.)

http://www.youtube.com/watch?v=kQI3AWpTWhM

I should add that this was a test flight done by the factory test pilot
and the wings were reinforced for this test. Standard wings would have
fallen off pretty quickly, as you can see in related videos.

[[email protected]]

>
> Relative to where it would start unloaded. IOW if you were overspeeding as
> a result of an unusual attitude recovery and you were pulling like hell at
> the same time, the flutter would appear at a lower airspeed than it would
> if you were just in a dive with the wing loaded at 1 G. Both of these
> speeds should still be over red-line.

Ah, I see, that makes it more clear. Interesting how flutter sounds so
benign (like a butterfly!) but is actually more like a quick trip to
the graveyard. However it must be a rare phenomenon because I never
came across the term in my PPL training and I don't remember even
seeing this topic discussed in any AOPA article in the last 2 years.

[F. Baum]

On Dec 25, 10:45*am, Bertie the Bunyip > wrote:

> Big flexible surfaces can flutter all by themselves *as shown in that
> clip of the A6 I posted and that might be what you mean about the Cl CG
> relationship. In fact that's one of the reasons that a wing mounted
> engine is a good idea and why the pods on jet airliners (which have the
> structural rigidity of Jel-lo) are mounted out in front. The change in
> CG helps dampen the flutter in the same way as mass balance on an
> aileron would.
>
Bertie, What are you trying to do here? Do you realize that your
respectful aviation related post will ruin this list for guys like Jay
and his petty abusive OT posts ?
FB

[Bertie the Bunyip[_19_]]

wrote in news:b98d38db-fc5c-4cc8-9272-
:

>> You'll get one of those thngs out of anywhere, but if the field is,
say,
>> 400 yards or more, you'll get an acrosport in and out of it easily.
Even
>> shorter if ou're sharp.
>>
>
> Suffice to say I'm pretty excited about the AcroSport, it's
> performance, and how you can fly it. Plus, it's a fabric covered
> biplane. How kick azz is that? Well, very.
>
> It's a longer term project though.
>
> I wonder if you could use a Mazda 13B -- should fit in the weight / hp
> range. Not many moving parts to break, either. Hmm. Don't know if
> anybody's done aerobatics with a 13B though.


You could, but It's easier and cheaper to use an airplane engine at the
end of the day. Unless it's your "thing" to mess with things like that.
If you're just looking to save money, forget it.
>
> I want to give a shot at plans building the 701. There's a nice set of
> videos that show quite a bit of the 701 construction sequence from
> those Canadian guys at Can Zac. I might buy some of it as a kit to
> save some time though.

Yeah, someone in my group built one fairly quickly. I haven't flown it
but I've eyed them up over the years. Not very fast, though.
You could prolly get an acrosport cheap enough partly finished or one
needing a recover.
>
> I suppose these thoughts are way off topic. To bring it back: I know
> of only one Zenith STOL that had structural failure probably due to
> flutter as a result of exceeding Vne: somebody dived an 801 at the
> ground and apprently ripped the wings off on the way down. NTSB report
> says both pilot and passenger had a good bit of THC in their blood ...
> only fatalities I know of in the STOL series from Zenith and clearly
> pilot caused.
>

Yipes.. The only thing I don;t like about those Zenairs is they are
very light indeed. That 6061 is beer can stuff really, but the airplanes
have a good record, so...
You might not need the STOL performance unless you're flying out of your
own driveway, though. they're pretty slow....


Bertie
>

[Bertie the Bunyip[_19_]]

WingFlaps > wrote in news:b113861f-e022-4153-b0e5-
:

>>
>> Don;t think what you're saying about the Cl and the GG realationship
of
>> the surface is correct, but I don't know for sure. The way most
control
>> surfaces are constructed would pretty much gauruntee that that is the
>> case ( skinny at the back) but it's the wing or stab that is th emore
>> important ingredient there anyway.
>
> Yes, I agree that the wing or stab is important -but control surface
> flutter (maybe more common in models with loose linkages) is bad too.
> Loss of the elevator is probably a terminal failure.
>

You're misunderstanding what I'm saying.

Control surface flutter is caused by a lack of rigidity in the wing.
Control surface flutter probably won't fail the surface itself, it wll
fail the surface it's attatched to. Your elevators prolly won't fall
off, but your stab will probsbly fail, or even the fuselage, long before
th ehinge lets go.

>> Big flexible surfaces can flutter all by themselves as shown in that
>> clip of the A6 I posted and that might be what you mean about the Cl
CG
>> relationship.
>
> Yes that's what I'm thinking about.

Those are unlikely in light planes.
>
>>In fact that's one of the reasons that a wing mounted
>> engine is a good idea and why the pods on jet airliners (which have
the
>> structural rigidity of Jel-lo) are mounted out in front. The change
in
>> CG helps dampen the flutter in the same way as mass balance on an
>> aileron would.
>
> A good point, I hadn't thought about engine pylons serving that
> function.



Bertie

[Bertie the Bunyip[_19_]]

wrote in
:

>
>>
>> Relative to where it would start unloaded. IOW if you were
>> overspeeding as a result of an unusual attitude recovery and you were
>> pulling like hell at the same time, the flutter would appear at a
>> lower airspeed than it would if you were just in a dive with the wing
>> loaded at 1 G. Both of these speeds should still be over red-line.
>
> Ah, I see, that makes it more clear. Interesting how flutter sounds so
> benign (like a butterfly!) but is actually more like a quick trip to
> the graveyard.

It is. I know someone who died doing aerobatics which induced flutter. It
was a Sonerai. Aileron flutter. It snapped the spar and the wing warapped
around the top of the canopy precluding his exit. He rode it in trying to
get it to roll to et the wing off and securing the airplane for impact at
the end. He was using this little VW powered airplane to try and compete in
competition aerobatics.It wasn't up to the task. I think there was a bit of
re-design of the aircraft after that.

However it must be a rare phenomenon because I never
> came across the term in my PPL training and I don't remember even
> seeing this topic discussed in any AOPA article in the last 2 years.

It's more common than you think. A lot of WX accidents, for instance, where
there is loss of control due to disorientation in cloud often ended up in
an inflight breakup precipitated by a spiral dive or other stressful flight
condition. Next time you see an airplane scattered across several fields,
you can be relatively certain that flutter did at least some of the damage
on the way down.



Bertie

[Bertie the Bunyip[_19_]]

"F. Baum" > wrote in news:8149eb30-36fe-4721-8858-
:

> On Dec 25, 10:45*am, Bertie the Bunyip > wrote:
>
>> Big flexible surfaces can flutter all by themselves *as shown in that
>> clip of the A6 I posted and that might be what you mean about the Cl CG
>> relationship. In fact that's one of the reasons that a wing mounted
>> engine is a good idea and why the pods on jet airliners (which have the
>> structural rigidity of Jel-lo) are mounted out in front. The change in
>> CG helps dampen the flutter in the same way as mass balance on an
>> aileron would.
>>
> Bertie, What are you trying to do here? Do you realize that your
> respectful aviation related post will ruin this list for guys like Jay
> and his petty abusive OT posts ?

God, I hope he told my IP tha! I clearly need to be stopped.


Bertie

[WingFlaps]

On Dec 26, 11:55 am, Bertie the Bunyip > wrote:

>
> Control surface flutter is caused by a lack of rigidity in the wing.
> Control surface flutter probably won't fail the surface itself, it wll
> fail the surface it's attatched to. Your elevators prolly won't fall
> off, but your stab will probsbly fail, or even the fuselage, long before
> th ehinge lets go.
>

Here's a case to think about:
http://www.flyingmag.com/article.asp?section_id=15&article_id=112&print_page=y

"It's hard to understand how a coat of paint can add three-quarters of
a pound to a surface area of only around 15 square feet, but the
National Transportation Safety Board's (NTSB) report on the accident
passes over this oddity without comment. Apparently, however,
investigators hypothesized that the other control surfaces, including
the mostly vanished rudder, might have been similarly overweight and
underbalanced, and Grob's analysts affirmed that rudder flutter was
possible under these conditions. The probable cause of the accident,
the NTSB concluded, was "failure of maintenance personnel to rebalance
the flight controls after the airplane had been repainted, which
resulted in rudder flutter and inflight breakup of the airplane."

The hinge allowed the rudder to drop off first followed by other bits.

Cheers

[[email protected]]

> Yipes.. *The only thing I don;t like about those Zenairs is they are
> very light indeed. That 6061 is beer can stuff really, but the airplanes
> have a good record, so...
> You might not need the STOL performance unless you're flying out of your
> own driveway, though. they're pretty slow....

Yup, slow. Check this out. If you could have a "favorite" NTSB
accident report, then this would be my favorite:

"As the pilot approached the vicinity of the destination airport, he
noted that the winds were about 35 to 40 miles per hour (mph). In
order to land into the wind he opted to perform a landing on a ramp
area of the airport. The airplane touched down on the ramp's surface
with a forward groundspeed of about 3 mph. A side load was placed on
the left main landing gear, and the tire subsequently deflated. The
airplane veered to the left and pitched forward, resulting in damage
to the firewall. A weather reporting station in the area reported
winds at 24 mph, gusting to 28 mph."

There's a lot of these flying and they have been around since
something like 1985 or so. Not many NTSB reports and no fatals.

Anyway it just looks like good plain fun.

[[email protected]]

> It's more common than you think. A lot of WX accidents, for instance, where
> there is loss of control due to disorientation in cloud *often ended up in
> an inflight breakup precipitated by a spiral dive or other stressful flight
> condition. Next time you see an airplane scattered across several fields,
> you can be relatively certain that flutter did at least some of the damage
> on the way down.

And it even happens to people like Scott Crossfield.

[[email protected]]

> "It's hard to understand how a coat of paint can add three-quarters of
> a pound to a surface area of only around 15 square feet, but the
> National Transportation Safety Board's (NTSB) report on the accident
> passes over this oddity without comment. Apparently, however,
> investigators hypothesized that the other control surfaces, including
> the mostly vanished rudder, might have been similarly overweight and
> underbalanced, and Grob's analysts affirmed that rudder flutter was
> possible under these conditions."

Hell.

Why paint?

[[email protected]]

> Here's a case to think about:http://www.flyingmag.com/article.asp?section_id=15&article_id=112&pri...

From this same article:

Flutter is usually associated with high speed, but low-speed aircraft
can also flutter if they are sufficiently flexible. In 1991 a
homebuilt amphibian crashed during an early test flight after one of
its external-airfoil flaperons fluttered, causing the left wing to
separate from the airplane. The builder-pilot was wearing a parachute,
but he bailed out at such a low altitude that there was insufficient
time for it to open. In this case, the builder had elected not to
install the "strongly recommended" balance weights on the flaperons
because they would make the airplane heavier, and he "felt that they
were not needed."

This makes me remember something I read in William Wynne's Corvair
conversion manual: "It's not the probability of being right, it's the
cost of being wrong."

I think I'll stick to the plans and have it checked by a third party.

[Bravo Two Zero]

"Stefan" > wrote in message
...
> Bravo Two Zero schrieb:
>
>> What is rudder flutter ?
>
> This is rudder flutter. (Actually, it's aileron flutter, but the principle
> is the same.)
>
> http://www.youtube.com/watch?v=kQI3AWpTWhM
>
> I should add that this was a test flight done by the factory test pilot
> and the wings were reinforced for this test. Standard wings would have
> fallen off pretty quickly, as you can see in related videos.


Thanks Guys espec. Bertie the Bunyip.

So the next question would be, if you experience rudder flutter in flight,
what would you do ( apart from prey !!!)

[WingFlaps]

On Dec 26, 7:38 pm, "Bravo Two Zero" > wrote:
> "Stefan" > wrote in message
>
> ...
>
> > Bravo Two Zero schrieb:
>
> >> What is rudder flutter ?
>
> > This is rudder flutter. (Actually, it's aileron flutter, but the principle
> > is the same.)
>
> >http://www.youtube.com/watch?v=kQI3AWpTWhM
>
> > I should add that this was a test flight done by the factory test pilot
> > and the wings were reinforced for this test. Standard wings would have
> > fallen off pretty quickly, as you can see in related videos.
>
> Thanks Guys espec. Bertie the Bunyip.
>
> So the next question would be, if you experience rudder flutter in flight,
> what would you do ( apart from prey !!!)

Reduce speed ASAP

Cheers

[Bertie the Bunyip[_19_]]

WingFlaps > wrote in
:

> On Dec 26, 11:55 am, Bertie the Bunyip > wrote:
>
>>
>> Control surface flutter is caused by a lack of rigidity in the wing.
>> Control surface flutter probably won't fail the surface itself, it
>> wll fail the surface it's attatched to. Your elevators prolly won't
>> fall off, but your stab will probsbly fail, or even the fuselage,
>> long before th ehinge lets go.
>>
>
> Here's a case to think about:
> http://www.flyingmag.com/article.asp?section_id=15&article_id=112
&print
> _page=y
>
> "It's hard to understand how a coat of paint can add three-quarters of
> a pound to a surface area of only around 15 square feet,



Pick up a can of paint sometime!


This is a relatively common problem, believe it or not. There have been
lots of accidents over the years on repainted aicraft. When Bonanazas
started to come apart in numbers large enough to catch the NTSB's
attention, at least a few of them were down to repaints without correct
balancing done afterwards.


but the
> National Transportation Safety Board's (NTSB) report on the accident
> passes over this oddity without comment. Apparently, however,
> investigators hypothesized that the other control surfaces, including
> the mostly vanished rudder, might have been similarly overweight and
> underbalanced, and Grob's analysts affirmed that rudder flutter was
> possible under these conditions. The probable cause of the accident,
> the NTSB concluded, was "failure of maintenance personnel to rebalance
> the flight controls after the airplane had been repainted, which
> resulted in rudder flutter and inflight breakup of the airplane."
>
> The hinge allowed the rudder to drop off first followed by other bits.


Yeah, but it probably fractured the fuselage just before it departed the
aircraft.. I remember reading the report on a lass glider that got
flutter momentarily in the elevator. The pilot managed to land it to
find the aft half of the fuselage was almost completely gone, the tail
held on only by threads.
I had a low freq tye of flutter once. I was flying a Twin Beech on a
sched pax service and after airborne on the second sector a hinged
inspection panel on the outboard section of the top wing opened (the
airplane had been on an inspection) and the panel, probably about
10"X6" flapped up and down and caused a sympathetic motion in the
aileron, probably a couple of Hz or so. There's a name for this kind of
flutter, but I can't remember it. We slowed down and the freq decreasd,
but I don't think it ever went away. It was more than a bit disturbing,
but fortunately the flight was relatively short.


Bertie

[Bertie the Bunyip[_19_]]

wrote in
:

>> Here's a case to think
>> about:http://www.flyingmag.com/article.asp?section_id=15&article_id=11
>> 2&pri...
>
> From this same article:
>
> Flutter is usually associated with high speed, but low-speed aircraft
> can also flutter if they are sufficiently flexible. In 1991 a
> homebuilt amphibian crashed during an early test flight after one of
> its external-airfoil flaperons fluttered, causing the left wing to
> separate from the airplane. The builder-pilot was wearing a parachute,
> but he bailed out at such a low altitude that there was insufficient
> time for it to open. In this case, the builder had elected not to
> install the "strongly recommended" balance weights on the flaperons
> because they would make the airplane heavier, and he "felt that they
> were not needed."
>
> This makes me remember something I read in William Wynne's Corvair
> conversion manual: "It's not the probability of being right, it's the
> cost of being wrong."
>
> I think I'll stick to the plans and have it checked by a third party.
>
Good plan. You'll find that the Acrosport probably doesn't have balance
weights on it because it's so rigid, but the 701 more than likely will have
quite large ones. IIRC all the control surfaces have very large aerodynamic
balance areas anyway, so it's very simple to add stips of lead in the
leading edge to bring them to the specified balance.
What you usually do is get a postage scale and put it under the trailing
edge after painting and add lead untio it gets to the specified weight.


Bertie

[Bertie the Bunyip[_19_]]

wrote in news:3d7e88e1-8aa9-449a-b6a9-
:

>> Yipes.. *The only thing I don;t like about those Zenairs is they are
>> very light indeed. That 6061 is beer can stuff really, but the
airplanes
>> have a good record, so...
>> You might not need the STOL performance unless you're flying out of
your
>> own driveway, though. they're pretty slow....
>
> Yup, slow. Check this out. If you could have a "favorite" NTSB
> accident report, then this would be my favorite:
>
> "As the pilot approached the vicinity of the destination airport, he
> noted that the winds were about 35 to 40 miles per hour (mph). In
> order to land into the wind he opted to perform a landing on a ramp
> area of the airport. The airplane touched down on the ramp's surface
> with a forward groundspeed of about 3 mph. A side load was placed on
> the left main landing gear, and the tire subsequently deflated. The
> airplane veered to the left and pitched forward, resulting in damage
> to the firewall. A weather reporting station in the area reported
> winds at 24 mph, gusting to 28 mph."


Yeah, done this in cubs and t-carts. Good fun!
Minus the last bit of course.
>
> There's a lot of these flying and they have been around since
> something like 1985 or so. Not many NTSB reports and no fatals.
>
> Anyway it just looks like good plain fun.


Mm, that is a god record. Usually some tit manages to kill himself doing
something incredibly stupid like opting to use some aluminum tubing he's
taken off an old deck chair or something. Or the guy you mentioned
before who left the balance weights off his airplane..


Bertie
>

[Bertie the Bunyip[_19_]]

wrote in
:

>> It's more common than you think. A lot of WX accidents, for instance,
>> wher
> e
>> there is loss of control due to disorientation in cloud *often ended
>> up
> in
>> an inflight breakup precipitated by a spiral dive or other stressful
>> fligh
> t
>> condition. Next time you see an airplane scattered across several
>> fields, you can be relatively certain that flutter did at least some
>> of the damage
>
>> on the way down.
>
> And it even happens to people like Scott Crossfield.
>

Yeah..

Bertie

[Bertie the Bunyip[_19_]]

"Bravo Two Zero" > wrote in
:

>
> "Stefan" > wrote in message
> ...
>> Bravo Two Zero schrieb:
>>
>>> What is rudder flutter ?
>>
>> This is rudder flutter. (Actually, it's aileron flutter, but the
>> principle is the same.)
>>
>> http://www.youtube.com/watch?v=kQI3AWpTWhM
>>
>> I should add that this was a test flight done by the factory test
>> pilot and the wings were reinforced for this test. Standard wings
>> would have fallen off pretty quickly, as you can see in related
>> videos.
>
>
> Thanks Guys espec. Bertie the Bunyip.
>
> So the next question would be, if you experience rudder flutter in
> flight, what would you do ( apart from prey !!!)
>
>
>

Bail out if I could. The airplane will probably be shredded. I've only ever
heard of one lightplane that survived a flutter incident. having said that,
the only ones you hear of are the ones that go in.

Bertie

[Bertie the Bunyip[_19_]]

WingFlaps > wrote in
:

> On Dec 26, 7:38 pm, "Bravo Two Zero" > wrote:
>> "Stefan" > wrote in message
>>
>> ...
>>
>> > Bravo Two Zero schrieb:
>>
>> >> What is rudder flutter ?
>>
>> > This is rudder flutter. (Actually, it's aileron flutter, but the
>> > principle is the same.)
>>
>> >http://www.youtube.com/watch?v=kQI3AWpTWhM
>>
>> > I should add that this was a test flight done by the factory test
>> > pilot and the wings were reinforced for this test. Standard wings
>> > would have fallen off pretty quickly, as you can see in related
>> > videos.
>>
>> Thanks Guys espec. Bertie the Bunyip.
>>
>> So the next question would be, if you experience rudder flutter in
>> flight, what would you do ( apart from prey !!!)
>
> Reduce speed ASAP

Yes, if you get it and the airplane stays together, but you have to
remember to be as smooth as possible in the recovery. Loading up the
airplane will exacerbate the problem. It;s test pilot stuff, really.
BTW, IIRC certification requirements for GA aricraft call for a dive to
10% above redline speed (might be lower for aircraft in the over 200
knot range) without any adverse effects. A place I used to work built
brand new Cessna 305s fom surplus parts and these had to be certified
locally under the builder's name. They were

Bertietest flown in this manner. IIRC the guy who did it took them up to
about 195 mph for certification.

The thing was so draggey he had to go near vertical to get that and I
don't think it would go any faster.

[B A R R Y]

On Wed, 26 Dec 2007 09:46:56 +0000 (UTC), Bertie the Bunyip >
wrote:
>
>Pick up a can of paint sometime!
>
>
>This is a relatively common problem, believe it or not.

Anyone remember the Eastern Airlines fuel savings claims when they
switched from a white base coat to natural aluminum?

Paint coats can have very noticeable weight.

[Bertie the Bunyip[_19_]]

B A R R Y > wrote in
:

> On Wed, 26 Dec 2007 09:46:56 +0000 (UTC), Bertie the Bunyip >
> wrote:
>>
>>Pick up a can of paint sometime!
>>
>>
>>This is a relatively common problem, believe it or not.
>
> Anyone remember the Eastern Airlines fuel savings claims when they
> switched from a white base coat to natural aluminum?
>
> Paint coats can have very noticeable weight.
>

Yep. that stuff can be heavy. My airpalne goes into the paint shop next
wekk and the instructions the shop has are to keep it as light as possible.

No paint on a tin airplane has the added bonus of making the airfram easier
to inspect for cracks and what not. On the minus side, they do corrode a
bit more easily..


Bertie

[Mxsmanic]

B A R R Y writes:

> Anyone remember the Eastern Airlines fuel savings claims when they
> switched from a white base coat to natural aluminum?
>
> Paint coats can have very noticeable weight.

Perhaps that's why American still has a mostly unpainted livery. Although I
don't know if the metal is actually bare or simply coated with something
protective and transparent.

[Bertie the Bunyip[_19_]]

Mxsmanic > wrote in
:

> B A R R Y writes:
>
>> Anyone remember the Eastern Airlines fuel savings claims when they
>> switched from a white base coat to natural aluminum?
>>
>> Paint coats can have very noticeable weight.
>
> Perhaps that's why American still has a mostly unpainted livery.
> Although I don't know if the metal is actually bare or simply coated
> with something protective and transparent.

Oh thanks for that,


Please don't post everything you don't know about aviation, you'l crash the
net.


Bertie
>