Question - rudder flutter ?

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

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

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

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.

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

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,

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

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.

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

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.