A B737-400 'a' hydraulic system leaked most of its fluid in-flight. QRH procedures preserved enough ...

Narrative:

While at cruise altitude a master caution came on with hydraulic advisory light illuminated. Observing the overhead panel no system lights were illuminated; looking at the quantity levels a system appeared to show empty. We then got a low pressure light on eng a system pump and completed QRH a system loss. Notified maintenance and elected to proceed to an alternate (longer runways; better weather) and had them give our ops a heads up as to the fact we may need a tow into the gate. Upon arrival at the alternate elected to turn electric pump back on and got the gear down normally; after landing reinstated electric pump again and were able to taxi to gate on our own (obviously able to trap fluid after QRH procedures). At the gate puddle under wing; aircraft right; looked to mechanics possible spoiler actuator or line.

Original NASA ASRS Text

Title: A B737-400 'A' hydraulic system leaked most of its fluid in-flight. QRH procedures preserved enough fluid for normal gear extension and taxi to the gate. An emergency was declared prior to landing.

Narrative: While at cruise altitude a master caution came on with HYD advisory light illuminated. Observing the overhead panel no system lights were illuminated; looking at the quantity levels A system appeared to show empty. We then got a low pressure light on Eng A system pump and completed QRH A system loss. Notified Maintenance and elected to proceed to an alternate (longer runways; better weather) and had them give our ops a heads up as to the fact we may need a tow into the gate. Upon arrival at the alternate elected to turn electric pump back on and got the gear down normally; after landing reinstated electric pump again and were able to taxi to gate on our own (obviously able to trap fluid after QRH procedures). At the gate puddle under wing; aircraft right; looked to Mechanics possible spoiler actuator or line.

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	835821
Time
Date	200905
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Make Model Name	B737-400
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Hydraulic System
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical

A B737-400 'a' hydraulic system leaked most of its fluid in-flight. QRH procedures preserved enough fluid for normal gear extension and taxi to the gate. An emergency was declared prior to landing.