Two hertz shake
On my recent 777-300ER flight LHR-YVR we had long periods (hours) of very light turbulence (until we passed Hudson Bay) and a very short period of light-medium turbulence going through heavy cloud leaving LHR (20 seconds.)
I was sitting directly over the wing and the very light turbulence always seemed to resolve into exactly the same 2hz movement roughly 5cm in amplitude from top-left to bottom-right.
It seems strange that what is essentially a random input should cause the fuselage to move so predictably (and annoyingly.)
It felt like an older open-top car that has been driven for years over potholes.
Surely this can't be good for metal fatigue reasons?
Does the 748 or 744 do this? I don't recall other planes shaking in similar ways.