I've spent a fair amount of time shaking stuff for shock and vibe testing... But it's usually just a fail check running an ATP on the hardware after testing.
How does this work for flutter?
So he's got a stinger exciting the wing tip (I'm guessing on a spar/compression rib??)
Then a few sensors to "map" the response. Its sitting on it's tires/shock absorbers...
He didn't have a lot of resolution with just 8 accelerometers... but was able to see how each one was phased to the other. They were feeling by hand to find nodal lines.
He determined that a node line intersected an aileron (honestly before doing anything) and suspected, the aileron was being balanced on one side of the line was insufficient.
He also commented that there was slop/play in the aileron that... what if it was excited by airflow the slop **could** allow it to set up at a resonance.
What kind of analysis did he actually do with that equipment? Looked like a bunch of practical intuition and a show with vintage equipment.