Would this plane have flown?

Dave Butler wrote:
Dave Stadt wrote:

"Dave Butler" wrote in message
news:1143124006.95524@sj-nntpcache-5...

Dylan Smith wrote:

On 2006-03-23, Morgans wrote:


Flutter scares the crap out of me.



I would strongly doubt (based on what I know) that there was even the
remotest chance of flutter. From what I understand, flutter would
require the flexing of the wing structure in such a way to cause the
whole thing to oscillate. This happens with experimental airframes (or
used to happen) because the whole surface or wing would warp under
aerodynamic loads in such a way that you'd get the oscillation. A dent
in a Mooney aileron isn't going to cause that.


FWIW, Mooney ailerons are required to be rebalanced after they are
*painted*.



As are almost all flight control surfaces on most all aircraft.


OK, I thought this requirement came from manufacturers service letters
and the like. I know about Bonanza and Mooney. Is there some other more
general requirement?

Here's a quote from http://www.avweb.com/news/maint/182829-1.html "Getting Good
Paint" by Paul Bertorelli:

"Guenther and better shops insist—rightly—that controls be removed, stripped,
inspected and, most important, rebalanced after painting. On some
controls—Bonanza ruddervators and Mooney ailerons—this is a critical task and
shouldn’t be skipped. But it should still be standard on all aircraft. Guenther
goes so far as to record the balance data in the aircraft logbook, along with
the signoff for the paint itself."

which makes me think this is not a general requirement or practice.

Flutter is determined by the torsional stiffness (and mass) of the wing
section. In this case, that did not seem to be compromised - i. e.
there were no diagonal wrinkles across the wing panel. If there were
diagonal wrinkles, flutter would be a real possibility. But dropping
the airspeed greatly helps the flutter margin, just as increasing the
max speed quickly reduces the flutter margin. I understand that during
each new aircraft's flight at the factory, the test pilot must dive it
to 110% of the indicated red line speed. The survivors are certfied.

There were diagonal wrinkles across the aileron panel, but I don't
think the aileron in itself can flutter. The question in this case
would be the aileron control integrity. Someone earlier suggested
blocking or locking one aileron. That could have all sorts of
interesting changes and very definitely I would not recommend.

Flutter is caused by imbalanced movable surfaces. When the
plane moves the moment arm of the surface causes deflection
of the surface.



--
James H. Macklin
ATP,CFI,A&P

--
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But government sees it as an obstacle to be overcome.
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See http://www.fija.org/ more about your rights and duties.


"nrp" wrote in message
oups.com...
| Flutter is determined by the torsional stiffness (and
mass) of the wing
| section. In this case, that did not seem to be
compromised - i. e.
| there were no diagonal wrinkles across the wing panel. If
there were
| diagonal wrinkles, flutter would be a real possibility.
But dropping
| the airspeed greatly helps the flutter margin, just as
increasing the
| max speed quickly reduces the flutter margin. I
understand that during
| each new aircraft's flight at the factory, the test pilot
must dive it
| to 110% of the indicated red line speed. The survivors
are certfied.
|
| There were diagonal wrinkles across the aileron panel, but
I don't
| think the aileron in itself can flutter. The question in
this case
| would be the aileron control integrity. Someone earlier
suggested
| blocking or locking one aileron. That could have all
sorts of
| interesting changes and very definitely I would not
recommend.
|

But I understand flutter also relies on the original torsional
stiffness of the wing being preserved. That if it is not (i. e. a
wrinkled wing skin) the flutter margin is reduced. Might even a
properly balanced control surface still flutter if the primary wing
stiffness is compromised? or is the control surface CG the only
determining item? THX

Wing stiffness has more to do with control reversal, flutter
has to do with harmonics and balance.

If I had a question about a control surface and I had to fly
the airplane, I would limit speed to Va so that even a full
deflection of the control would not break the airplane.


I've seen pictures of a C210 [old plane with struts] that
took off from a strip near Tulsa with just a little ice on
the ailerons. I got to cruise speed and crashed shortly
there after, the outer wing panels looked like a Navy
fighter with the wings folded.


--
James H. Macklin
ATP,CFI,A&P

"nrp" wrote in message
oups.com...
| But I understand flutter also relies on the original
torsional
| stiffness of the wing being preserved. That if it is not
(i. e. a
| wrinkled wing skin) the flutter margin is reduced. Might
even a
| properly balanced control surface still flutter if the
primary wing
| stiffness is compromised? or is the control surface CG the
only
| determining item? THX
|

In article .com,
"nrp" wrote:

But I understand flutter also relies on the original torsional
stiffness of the wing being preserved. That if it is not (i. e. a
wrinkled wing skin) the flutter margin is reduced. Might even a
properly balanced control surface still flutter if the primary wing
stiffness is compromised? or is the control surface CG the only
determining item? THX


Flutter can also result from unusual airflow exciting a surface (such as
the rather large dent in the aileron tip). It is a function of
stiffness, true airspeed, balance and external excitations.

The owner did the conservative thing -- after all his insurance company
was there to stand behind him. Yes -- the whole thing was obviously a
major PITA, but everyone came out fine. Congratulations!

"Dave Butler" wrote in message
news:1143128184.860637@sj-nntpcache-3...
Dave Butler wrote:
Dave Stadt wrote:

"Dave Butler" wrote in message
news:1143124006.95524@sj-nntpcache-5...

Dylan Smith wrote:

On 2006-03-23, Morgans wrote:


Flutter scares the crap out of me.



I would strongly doubt (based on what I know) that there was even the
remotest chance of flutter. From what I understand, flutter would
require the flexing of the wing structure in such a way to cause the
whole thing to oscillate. This happens with experimental airframes (or
used to happen) because the whole surface or wing would warp under
aerodynamic loads in such a way that you'd get the oscillation. A dent
in a Mooney aileron isn't going to cause that.


FWIW, Mooney ailerons are required to be rebalanced after they are
*painted*.



As are almost all flight control surfaces on most all aircraft.


OK, I thought this requirement came from manufacturers service letters
and the like. I know about Bonanza and Mooney. Is there some other more
general requirement?

Here's a quote from http://www.avweb.com/news/maint/182829-1.html "Getting
Good Paint" by Paul Bertorelli:

"Guenther and better shops insist—rightly—that controls be removed,
stripped, inspected and, most important, rebalanced after painting. On
some controls—Bonanza ruddervators and Mooney ailerons—this is a critical
task and shouldn’t be skipped. But it should still be standard on all
aircraft. Guenther goes so far as to record the balance data in the
aircraft logbook, along with the signoff for the paint itself."

which makes me think this is not a general requirement or practice.

It is. Most all manufacturers provide control surface balance requirements.
Even the Cessna 150 requires it. I also believe it is in the FARs.