Flight Data Recorder

What does "sampling rate" mean with regard to recording of acceleration data which is essential for hard landing analysis?

Without digging into manuals, I would guess sampling rate is how quickly data is updated.

All aircraft systems data is reported to the DFDAU. It sends data to the FDR, WQAR (if installed), and it usually has its own PCMCIA card for recording also.

This data (via 429 or any other type of data bus) is sent in kilo/seconds or faster.

Please reference  en.wikipedia.org/wiki/ARINC_429

Acceleration data (in the case of a 767) is not a data-bus signal. It looks to be a constant output for lateral, longitudinal, and vertical sent to the DFDAU.

Pitch, roll, yaw, vertical speed, and other flight related data "is" sent via 429 from the IRU's to the DFDAU.