The quill shaft had sheared. The other pump I was flying on had 600 hours more than the one that had failed.
The qestion this raises to me was "what were the criteria for inspection the pump (and its piece parts)" to determine the "condition" of the pump.
(PS, is the quill shaft that which drives the pump from the transmission, or is it something else? )
(Aren't you glad there were 2?
)
Looks like we are in a bit of thread drift, I'll stop there, even though "shaft failure" looks to be a common theme.