Boeing Hydraulics
Hi everyone,
On 767/747-400 (and perhaps other Boeings I'm not aware of) when you pressurize the hyd system before start-up you should turn the right hyd system (No 4 demand pump on the 747) first by the Boeing normal procedure. The short explanation by Boeing is: "to prevent fluid transfer".
But fluid transfer between totally separate systems??? To my knowledge the system is designed to prevent transfer and loss of fluid in case of a failure (ruptured duct). And transfer from the left systems to the no 4 only?? And no transfer the other way round?
Studying the system diagrams in the AOM will not help.
Any explanation is welcomed,
b