Loss of the left hydraulic system became a complete loss of both systems when the right system, whic...

Attributes
ACN	110135
Time
Date	198905
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : rwf
State Reference	MN
Altitude	msl bound lower : 33000 msl bound upper : 33000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zmp
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 210 flight time total : 7500 flight time type : 125
ASRS Report	110134
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : instrument pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 120 flight time total : 7000 flight time type : 220
ASRS Report	110218
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	none taken : unable
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

One hour after takeoff left hydraulic quantity had decreased to 6 qts. Further observation showed that the left quantity gradually was decreasing even further. All other indications being normal, we accomplished appropriate checklist for current situation. After notifying maintenance about the situation, the decision was unanimously made to continue to our destination (given current situation, ie, location/weight of aircraft and alternate airports). Some time after the conversation with tulsa maintenance the left quantity continued to decrease to 0 qts, at which time a grinding noise became prevalent. Shortly after several surges in the system, both hydraulic pressures dropped to 0 and both hydraulic low pressure lights came on. After further checklists, operating manual considerations and conversation with tulsa maintenance, the plan remained to continue the flight to chicago. After the current update of the WX in chi proved that the WX had deteriorated to the point to go to the alternate airport of minneapolis (considerations of dry runway vs wet runway, etc). After some discussion with maintenance personnel on the ground at minneapolis, the problem appears to be one that is of a rare occurrence for this particular type aircraft and design. Possible action in the future should be given to expanding certain portions of the chklistsecond officerps manual relating to the hydraulic system as independent of each other, and the connection between to 2 systems in case one system malfunctions in connection with the possibility of landing at nearest suitable airport given the complexity of the problem. Supplemental information from acn 110218: there is no recommendation in the loss of one hydraulic system procedure to consider landing as soon as possible, so this probably influenced us early in the problem--although in this case the outcome would have been the same.

Original NASA ASRS Text

Title: LOSS OF THE LEFT HYDRAULIC SYSTEM BECAME A COMPLETE LOSS OF BOTH SYSTEMS WHEN THE RIGHT SYSTEM, WHICH WAS THOUGHT TO BE COMPLETELY ISOLATED FROM THE LEFT, PUMPED ITSELF OVERBOARD THROUGH THE LEAK IN THE LEFT SYSTEM.

Narrative: ONE HR AFTER TKOF LEFT HYD QUANTITY HAD DECREASED TO 6 QTS. FURTHER OBSERVATION SHOWED THAT THE LEFT QUANTITY GRADUALLY WAS DECREASING EVEN FURTHER. ALL OTHER INDICATIONS BEING NORMAL, WE ACCOMPLISHED APPROPRIATE CHKLIST FOR CURRENT SITUATION. AFTER NOTIFYING MAINT ABOUT THE SITUATION, THE DECISION WAS UNANIMOUSLY MADE TO CONTINUE TO OUR DEST (GIVEN CURRENT SITUATION, IE, LOCATION/WT OF ACFT AND ALTERNATE ARPTS). SOME TIME AFTER THE CONVERSATION WITH TULSA MAINT THE LEFT QUANTITY CONTINUED TO DECREASE TO 0 QTS, AT WHICH TIME A GRINDING NOISE BECAME PREVALENT. SHORTLY AFTER SEVERAL SURGES IN THE SYS, BOTH HYD PRESSURES DROPPED TO 0 AND BOTH HYD LOW PRESSURE LIGHTS CAME ON. AFTER FURTHER CHKLISTS, OPERATING MANUAL CONSIDERATIONS AND CONVERSATION WITH TULSA MAINT, THE PLAN REMAINED TO CONTINUE THE FLT TO CHICAGO. AFTER THE CURRENT UPDATE OF THE WX IN CHI PROVED THAT THE WX HAD DETERIORATED TO THE POINT TO GO TO THE ALTERNATE ARPT OF MINNEAPOLIS (CONSIDERATIONS OF DRY RWY VS WET RWY, ETC). AFTER SOME DISCUSSION WITH MAINT PERSONNEL ON THE GND AT MINNEAPOLIS, THE PROB APPEARS TO BE ONE THAT IS OF A RARE OCCURRENCE FOR THIS PARTICULAR TYPE ACFT AND DESIGN. POSSIBLE ACTION IN THE FUTURE SHOULD BE GIVEN TO EXPANDING CERTAIN PORTIONS OF THE CHKLISTS/OPS MANUAL RELATING TO THE HYD SYS AS INDEPENDENT OF EACH OTHER, AND THE CONNECTION BTWN TO 2 SYSTEMS IN CASE ONE SYS MALFUNCTIONS IN CONNECTION WITH THE POSSIBILITY OF LNDG AT NEAREST SUITABLE ARPT GIVEN THE COMPLEXITY OF THE PROB. SUPPLEMENTAL INFO FROM ACN 110218: THERE IS NO RECOMMENDATION IN THE LOSS OF ONE HYD SYS PROC TO CONSIDER LNDG ASAP, SO THIS PROBABLY INFLUENCED US EARLY IN THE PROB--ALTHOUGH IN THIS CASE THE OUTCOME WOULD HAVE BEEN THE SAME.

Data retrieved from NASA's ASRS site as of August 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.

Loss of the left hydraulic system became a complete loss of both systems when the right system, which was thought to be completely isolated from the left, pumped itself overboard through the leak in the left system.