Air carrier large transport suffers loss of 'a' system while in approach procedure for landing.

Attributes
ACN	204719
Time
Date	199203
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : sfo
State Reference	CA
Altitude	msl bound lower : 6000 msl bound upper : 6000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sfo tower : oma
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent : approach
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : commercial pilot : atp pilot : instrument
Experience	flight time last 90 days : 150 flight time total : 6000 flight time type : 2000
ASRS Report	204719
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 10000 flight time type : 6000
ASRS Report	204710
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : declared emergency none taken : unable other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

On right downwind for runway 28R at sfo, I called for 'flaps 2.' the PNF selected laps 2 and the so noticed a rapid decrease in system a hydraulic quantity and pressure. At this time, we notified ATC and requested priority handling. We took delay vectors so as to accomplish appropriate checklists. SOP followed. Once all checklist items were complete the captain took control of the aircraft to make the approach and landing to the airport. Approach and landing uneventful.

Original NASA ASRS Text

Title: ACR LGT SUFFERS LOSS OF 'A' SYS WHILE IN APCH PROC FOR LNDG.

Narrative: ON R DOWNWIND FOR RWY 28R AT SFO, I CALLED FOR 'FLAPS 2.' THE PNF SELECTED LAPS 2 AND THE SO NOTICED A RAPID DECREASE IN SYS A HYD QUANTITY AND PRESSURE. AT THIS TIME, WE NOTIFIED ATC AND REQUESTED PRIORITY HANDLING. WE TOOK DELAY VECTORS SO AS TO ACCOMPLISH APPROPRIATE CHKLISTS. SOP FOLLOWED. ONCE ALL CHKLIST ITEMS WERE COMPLETE THE CAPT TOOK CTL OF THE ACFT TO MAKE THE APCH AND LNDG TO THE ARPT. APCH AND LNDG UNEVENTFUL.

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.