See query.
Still in use?
Yes, still in use.
It means a landing so smooth it’s hard to tell just when the wheels touch the ground.
I don’t know it’s origin but it means an incredibly smooth landing, no bump, no sound. I haven’t heard it myself for some years because I haven’t been hanging out with pilots that much, but I don’t know why they wouldn’t keep saying it.
Tanks.
Tanks always go thunk when they land.
Absent a truly serious amount of grease.
The B-36, a really fucking big piston-engined bomber built after WWII, actually was tested with a tracked landing gear like a tank.