B737 flight crew experienced hydraulic system a anomalies after the #1 engine pump had been replaced...

Narrative:

Plane had #1 eng hydraulic pump replaced just before flight. Upon placing gear handle up after takeoff; both 'sys a hyd' lights illuminated momentarily; with no noticeable system deficiency. Near top of climb 'sys a hyd pump' illuminated; no loss of pressure or quantity. Followed QRH; conferred with dispatch who talked to maintenance; decision to continue and monitor was agreed. At top of climb quantity 'a' started to fluctuate; from 92% then 106%; then 88%. At that point sys 'a' quantity started decreasing. Conferred with dispatch on divert location. Declared emergency with ATC for landing ZZZ full stop on runway to have landing gear pinned. Ran checklist to include reviewed loss of system a and manual extension of landing gear. Briefed flight attendants of situation; PA's made to passengers; uneventful landing. After 30 minute wait on runway; landing gear pinned and towed to gate. Declined reschedule of flight due to fatigue and safety (already tired and unsure of late adrenaline rush; first flight after vacation). Would have arrived destination at roughly 0330 local time.

Original NASA ASRS Text

Title: B737 flight crew experienced hydraulic system A anomalies after the #1 engine pump had been replaced just before departure. When fluid quantity began to decline the crew declared an emergency and returned to the departure airport.

Narrative: Plane had #1 Eng Hydraulic pump replaced just before flight. Upon placing gear handle up after takeoff; both 'Sys A Hyd' lights illuminated momentarily; with no noticeable system deficiency. Near top of climb 'Sys A Hyd Pump' illuminated; no loss of pressure or quantity. Followed QRH; conferred with Dispatch who talked to Maintenance; decision to continue and monitor was agreed. At top of climb quantity 'A' started to fluctuate; from 92% then 106%; then 88%. At that point Sys 'A' quantity started decreasing. Conferred with Dispatch on divert location. Declared emergency with ATC for landing ZZZ full stop on runway to have landing gear pinned. Ran checklist to include reviewed loss of system A and manual extension of landing gear. Briefed Flight Attendants of situation; PA's made to passengers; uneventful landing. After 30 minute wait on runway; landing gear pinned and towed to gate. Declined reschedule of flight due to fatigue and safety (already tired and unsure of late adrenaline rush; first flight after vacation). Would have arrived destination at roughly 0330 local time.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	853313
Time
Date	200909
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Night
Aircraft 1
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Hydraulic Fluid
Person 1
Function	Captain Pilot Not Flying
Person 2
Function	First Officer Pilot Flying
Events
Anomaly	Aircraft Equipment Problem Critical

B737 flight crew experienced hydraulic system a anomalies after the #1 engine pump had been replaced just before departure. When fluid quantity began to decline the crew declared an emergency and returned to the departure airport.