B737-300 had 'a' system hydraulic failure in ZAU class a airspace.

Attributes
ACN	493734
Time
Date	200011
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sbn.airport
State Reference	IN
Altitude	msl single value : 28000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau.artcc
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : multi engine pilot : atp pilot : cfi
Experience	flight time total : 13880 flight time type : 3363
ASRS Report	493734
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : multi engine
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : hyd low pressure low quantity other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance controller : provided flight assist flight crew : landed in emergency condition flight crew : diverted to another airport flight crew : declared emergency
Consequence	other other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

Just after level off at FL280, we noticed that hydraulic 'a' system quantity and pressure went to zero. We proceeded to the checklist. I then contacted dispatch and said that we had lost 'a' system hydraulics and wanted to return to ord. He agreed and said that he would advise of our return and would have emergency equipment standing by. We got ATC clearance back to ord. We had an uneventful landing runway 27L at ord. We were able to taxi clear of runway and then were towed to the gate.

Original NASA ASRS Text

Title: B737-300 HAD 'A' SYS HYD FAILURE IN ZAU CLASS A AIRSPACE.

Narrative: JUST AFTER LEVEL OFF AT FL280, WE NOTICED THAT HYD 'A' SYS QUANTITY AND PRESSURE WENT TO ZERO. WE PROCEEDED TO THE CHKLIST. I THEN CONTACTED DISPATCH AND SAID THAT WE HAD LOST 'A' SYS HYDS AND WANTED TO RETURN TO ORD. HE AGREED AND SAID THAT HE WOULD ADVISE OF OUR RETURN AND WOULD HAVE EMER EQUIP STANDING BY. WE GOT ATC CLRNC BACK TO ORD. WE HAD AN UNEVENTFUL LNDG RWY 27L AT ORD. WE WERE ABLE TO TAXI CLR OF RWY AND THEN WERE TOWED TO THE GATE.

Data retrieved from NASA's ASRS site as of July 2007 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.