Same with doing cliff winching in an updraft in the Sea King Syd - no chance of reading any instruments at all.
The effect of which I speak is quite subtle. Seeing the instruments was not a problem.
I suspect that your vibration is likely to be caused by interaction with complex vortices, as is the vibration of translational lift.
However the inflow angle changes at the rear as well with the front seeing a bigger change than the rear, hence the dissymmetry.
I should have said that it 'progressses from the front to the rear'.
In a still air transition the inflow roll happens first, then the flapback and then, when you overcome both, the vibration of ETL.
Yup. ;-)