B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 153; Flight Crew Total 2356; Flight Crew Type 2356
Aircraft Equipment Problem Critical
General Flight Cancelled / Delayed; General Maintenance Action
Aircraft; Procedure
By following the new SOP which requires the hydraulic electric pumps to be turned off during the walk around; the First Officer was not able to ascertain the fact that we had a significant hydraulic leak. It was only after the pumps were turned on several minutes later during the First Officer cockpit flows that the leak started. Luckily; a ramper spotted the leak and notified maintenance. Maintenance in turn told us; and then diagnosed the leak issue. Maintenance Control ultimately determined not to operate the airplane; and we swapped airplanes. Bottom line; the safe operation should not rest upon the keen eyes of a ramp employee. If we had the pumps on the way we used to for years; this would have been noticed by the First Officer; and the reporting/diagnosing/swap process could have started much sooner.
B737 Captain reported hydraulic leak detected by ramp personnel; indicative of flight crew preflight procedural revision required.