Thanks soem dood.
I oversimplified my description of the performance of a switched channel A/D by just combining the Nyquest minimum sample rate and the switching rate to sample two separate fuel system samples.
I plead laziness.
To atone, I looked up the performance of the 777 DFDR.
The DFDR in the 777 appears to record 128 samples / word per second. The parameters of interest to fuel flow and engine performance are sampled once a second.
This gives a maximum sampled frequency of 0.5Hz.
No fluidic resonance recording for you.
http://www.tc.faa.gov/its/worldpac/techrpt/ar06-11.pdf