Wing Bending Oscillation

Earlier, jcarlyle wrote:

2. How would he go about obtaining it? Accelerometer and frequency
counter? Stopwatch?

The latter.

I've heard that it used to be common practice to establish the
first-order symmetrical (I think) oscillation by wiggling one wingtip
up and down, and timing the cycles. If the frequency was substantially
different from that specified, it was considered cause for concern that
the wing's structure might have been compromised.

I think that this practice might have been of merit back in the says of
wooden gliders and iron pilots, but I've not heard of it considered a
standard practice for twenty years, maybe thrity. Nevil Shute wrote of
it in his autobiography _Slide Rule_.

Thanks, and best regards

Bob K.
http://www.hpaircraft.com/hp-24

"Bob Kuykendall" wrote in message
oups.com...
Earlier, jcarlyle wrote:

2. How would he go about obtaining it? Accelerometer and frequency
counter? Stopwatch?

The latter.

I've heard that it used to be common practice to establish the
first-order symmetrical (I think) oscillation by wiggling one wingtip
up and down, and timing the cycles. If the frequency was substantially
different from that specified, it was considered cause for concern that
the wing's structure might have been compromised.

I think that this practice might have been of merit back in the says of
wooden gliders and iron pilots, but I've not heard of it considered a
standard practice for twenty years, maybe thrity. Nevil Shute wrote of
it in his autobiography _Slide Rule_.

Thanks, and best regards

Bob K.
http://www.hpaircraft.com/hp-24


I remember that with wooden gliders. The wing shaking process would
occasionally elicit questions from bystanders. To which we would soberly
reply that the purpose was to inform the termites that we were going to fly
the glider and that they should hold hands to help keep it together.

Wing shaking was abandoned sometime around the time that large span
fiberglass gliders were intorduced. I recall seeing someone voilently shake
the tip of a ASW22, I think. This produced a wave in the wing that traveled
to the opposite tip, where it was reflected, returning to wrench the wingtip
from the pilots grip smacking him in the chin.

Bill Daniels

Thanks to you all for taking the time to respond. I learned something!

Initially I thought the wing oscillation rate had something to do with
flutter prevention or attachment integrity. When I was being taught how
to preflight the instructor told me he once found a wing that wasn't
properly attached by shaking a tip.

If wing frequency was being used for wing structural integrity testing
years ago, I'm glad to hear that it's been abandoned! Flaws that can
cause structural failure are much too small to affect a fundamental
resonant frequency.

I can believe that looking for odd ripples or bulges on the wing
surfaces during shaking could be useful indicators of problems, though,
so I, too, will keep it as part of my preflight. I won't bother to
measure the frequency, though.

-John

jcarlyle wrote:
Thanks to you all for taking the time to respond. I learned something!

Initially I thought the wing oscillation rate had something to do with
flutter prevention or attachment integrity. When I was being taught how
to preflight the instructor told me he once found a wing that wasn't
properly attached by shaking a tip.

If wing frequency was being used for wing structural integrity testing
years ago, I'm glad to hear that it's been abandoned! Flaws that can
cause structural failure are much too small to affect a fundamental
resonant frequency.

I can believe that looking for odd ripples or bulges on the wing
surfaces during shaking could be useful indicators of problems, though,
so I, too, will keep it as part of my preflight. I won't bother to
measure the frequency, though.

Guess I should tell the instructors that recommended it that their info
is a bit dated, 'course they are too. :-)

Shawn