B737-500 aircraft has failure of 'a' hydraulic system while taxiing for takeoff at ord.

Attributes
ACN	718204
Time
Date	200611
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : zzz.airport
State Reference	US
Altitude	agl single value : 0
Environment
Flight Conditions	VMC
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B737-500
Operating Under FAR Part	Part 121
Flight Phase	ground : pushback
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 21 flight time total : 7500 flight time type : 460
ASRS Report	718204
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 150 flight time total : 18800 flight time type : 3000
ASRS Report	717780
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	aircraft equipment other aircraft equipment : hyd press low light other flight crewa other flight crewb
Resolutory Action	none taken : anomaly accepted
Consequence	other other
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Aircraft

Narrative:

After engine start and initial taxi; lost entire 'a' system hydraulics on the ramp. Master caution/hydraulic light illuminated on panel. A system 'low pressure' light was on. Hydraulic quantity was depleting rapidly; and ramp called to notify us that we were spilling large quantities of hydraulic fluid. We stopped taxiing; set the parking brake; turned off the a electric and engine pumps; notified ramp that we would be shutting down engines; and requested emergency equipment to inspect the aircraft. After aircraft inspection; towed back to the gate by maintenance. Maintenance informed us that a seal blew out. Aircraft repaired and returned to service for a 4 hour late departure.

Original NASA ASRS Text

Title: B737-500 ACFT HAS FAILURE OF 'A' HYD SYS WHILE TAXIING FOR TKOF AT ORD.

Narrative: AFTER ENG START AND INITIAL TAXI; LOST ENTIRE 'A' SYS HYDS ON THE RAMP. MASTER CAUTION/HYD LIGHT ILLUMINATED ON PANEL. A SYS 'LOW PRESSURE' LIGHT WAS ON. HYD QUANTITY WAS DEPLETING RAPIDLY; AND RAMP CALLED TO NOTIFY US THAT WE WERE SPILLING LARGE QUANTITIES OF HYD FLUID. WE STOPPED TAXIING; SET THE PARKING BRAKE; TURNED OFF THE A ELECTRIC AND ENG PUMPS; NOTIFIED RAMP THAT WE WOULD BE SHUTTING DOWN ENGS; AND REQUESTED EMER EQUIP TO INSPECT THE ACFT. AFTER ACFT INSPECTION; TOWED BACK TO THE GATE BY MAINT. MAINT INFORMED US THAT A SEAL BLEW OUT. ACFT REPAIRED AND RETURNED TO SVC FOR A 4 HR LATE DEP.

Data retrieved from NASA's ASRS site as of January 2009 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.