wrote:
Checking a wing?s frequency is still a valid inspection technique.
I am looking at a document from HPH titled ?Ground Vibration Test
Report?, dated 11 April 2000 it refers to the checking of a new 304CZ.
It lists the air temperature, tire pressure and a brief outline of the
method used. As far as I know this test is still done by the other
glider factories as well.

Robert's post is most interesting, because it indicates that HPH
considers wing frequency measurement part of a Ground Vibration Test.
The GVT, which is usually done with instrumented hammers or shakers and
a large number of accelerometers, is a form of modal analysis.

One of the major purposes of a GVT is to help determine an aircraft's
susceptibility to flutter. If glider manufacturers consider checking
the wing oscillation frequency a means to forestall flutter, then we
should all be doing this test annually!

Robert, can you provide a URL to the HPH report you mentioned? Or could
you scan it and post it on the web? I, for one, would be most
interested in seeing it!

-John