So the state of play may be summed up as:
The wing bending frequency test may not detect
even quite significant spar damage that is
detectable by overt or less obvious means (tap test).
It may cause a glider to fail the test where
there is no obvious cause and the glider is
grounded. Might be an idea to find another glider
of the same type and measure its wing bending
frequency and or find the last few years' history of the measurement.
It can lead to further investigation which finds a problem
Hmmmm....
This also means there could be cases where the
wing bending frequency test is OK but other hidden damage could exist.
If you want to do this test properly, the right
way nowadays is to tape a small MEMS
accelerometer to the wingtip and record the
readings say 20 times a second or more.
This device looks good and is wireless:
http://axivity.com/files/resources/WAX3_Data_Sheet.pdf
Probably good enough to tell if there is indeed a temperature sensitivity also.
Good of you guys to think to do a wing bending
frequency test on something obviously damaged,
John, rather than just repair it right away.
Mike
At 09:34 AM 12/2/2015, you wrote:
More than one case of the test not revealing a failure.
An Astir CS which had been in a trailing crash.
The underside of the wing about 1 metre from the
root had an obvious impact over the spar region.
The frequency test did not show any significant
change. However when the damaged area was opened
for repair it revealed significant damage to the spar cap and web.
Regards,
John Orton
On 2 December 2015 at 08:48, Mark Newton
<<mailto:[email protected]>[email protected]> wrote:
On 1 Dec 2015, at 9:42 PM, Justin Couch
<<mailto:[email protected]>[email protected]> wrote:
> There is also one case where it didn't
(Bathurst's DG300 that delaminated the spar
caps from the wing didn't pick up a freq change, but the tap test did).
Interesting - Iâve spoken to Brits who had
never heard of the tap test and were a bit
bemused at Australiaâs seeming obsession with
it when they found out about it.
Nice to know that it might be useful for something :-)
 - mark
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