On Friday, March 4, 2016 at 4:39:05 PM UTC-5, wrote:
I have written an app that measures wing frequency - currently available for Android on the Play Store he https://play.google.com/store/apps/d...j.ios.wingfreq.

An IOS version will be available once I jump through the various hoops Apple places in the way.

Video of it in action he https://youtu.be/dBJOBxGWtCQ.

Clyde.

The easy and revealing part of the test, is to observe the wing tip
phase; in the first bending mode they should be synchronised within inches of each other. A wing lagging in phase would indicated spar or skin damage.
This is probably more accurate than the frequency test.
JMF