this had an engine driven fuel pump and standby pump for each engine....Is this not the case with the larger PT-6s as fitted to the PC-12?
The PT6-67B on the PC-12 has a similar configuration; wherein, the loss of the low pressure engine driven pump (43 psi output) can be replaced by fuel boost pumps (31 psi output) located in the fuel tanks. If fuel pressure drops below 2 psi (possible low pressure pump failure or clogged filter), the boost pumps are automatically activated to continuously provide fuel to the high pressure pump.
However, the high pressure pump (800 psi at 100% Ng) that supplies fuel to the FCU has no redundant system. I think most PT6 installations are so configured (anybody?). I guess you'd have to ask Pratt about the engineering logic behind this single point of failure.
FoF