B737-300
Flight Crew Last 90 Days 149; Flight Crew Type 14000
Troubleshooting; Training / Qualification
Aircraft Equipment Problem Critical
General Flight Cancelled / Delayed; General Maintenance Action
Procedure; Chart Or Publication; Aircraft
I was part of an originating (first flight of the day) crew for this aircraft. During preflight cockpit flows; placing either of the guarded hydraulic switches to standby failed to activate the Standby Hydraulic/Rudder System. This test of the Standby Hydraulic System by means of a Standby Rudder Check was a part of an originating preflight procedure at our Company from at least the time I was hired in until approximately six months ago when it was removed from our AOM; (Flight Deck Prep). On this particular originating preflight; my old habit pattern resulted in testing and subsequently discovering a complete failure of the Standby Hydraulic System. All the normal protocols involving Dispatch/Maintenance Control/Contract Maintenance and maintenance documentation were followed. When I left the aircraft; Contract Maintenance was still troubleshooting and had already determined that the electric powered standby hydraulic pump did not appear to be receiving power. Although I was not required to perform a standby rudder check; my concern is how long was this particular aircraft flying without a properly operating Standby Hydraulic System? How long would it be before a routine maintenance inspection would reveal the failure? Why was this check removed? What was the rational? Is it the feeling that we would have to lose both Hydraulic A and B systems to need the standby? As a high time Captain in the B737; it makes me uncomfortable knowing that I could have been flying this aircraft without standby rudder/hydraulics. Did we do the right thing by removing this check from our originating aircraft procedures?
A B737-300 Captain discovered the Standby Hydraulic/Rudder System inoperative after inadvertantly performing the system preflight check which had been removed as a preflight requirement about six months prior.