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A B737-700 in cruise at FL330 diverted due to slow loss of 'a' system hydraulic quantity. Caused by chaffed hydraulic line in left flap well.
| Attributes | |
| ACN | 520861 |
| Time | |
| Date | 200108 |
| Day | Sun |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : ewr.airport |
| State Reference | NV |
| Altitude | msl single value : 33000 |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zdc.artcc |
| Operator | common carrier : air carrier |
| Make Model Name | B737-700 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : air carrier |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 60 flight time total : 6500 flight time type : 2000 |
| ASRS Report | 520861 |
| Person 2 | |
| Affiliation | company : air carrier |
| Function | flight crew : captain oversight : pic |
| Events | |
| Anomaly | aircraft equipment problem : critical other anomaly other |
| Independent Detector | aircraft equipment other aircraft equipment : a system hydraulic qty other flight crewa other flight crewb |
| Resolutory Action | flight crew : diverted to another airport |
| Consequence | other |
| Supplementary | |
| Problem Areas | Aircraft |
| Primary Problem | Aircraft |
Narrative:
Shortly after leveloff in cruise, captain noticed a drop in system 'a' hydraulic quantity (no warning or lights). The system was noted to be losing approximately 1% per min. The flight crew conferred, including the international relief officer, then the captain conferred with system control and maintenance control. It was decided to return to ewr. QRH was reviewed, and kept open to loss of system 'a.' in terminal area (ewr) engine #1 hydraulic pump low pressure light came on. The QRH was consulted, the pump switch was turned off per the checklist. An uneventful landing was made with all system operating normally except for the #1 engine driven hydraulic pump off. Hydraulic quantity stabilized at 25%. Callback conversation with reporter revealed the following information: the reporter stated the airplane was a B737-700. The reporter said the cause of the loss of 'a' system hydraulic fluid was a chaffed line in the left flap well just outboard of the main wheel well.
Original NASA ASRS Text
Title: A B737-700 IN CRUISE AT FL330 DIVERTED DUE TO SLOW LOSS OF 'A' SYS HYD QUANTITY. CAUSED BY CHAFFED HYD LINE IN L FLAP WELL.
Narrative: SHORTLY AFTER LEVELOFF IN CRUISE, CAPT NOTICED A DROP IN SYS 'A' HYD QUANTITY (NO WARNING OR LIGHTS). THE SYS WAS NOTED TO BE LOSING APPROX 1% PER MIN. THE FLC CONFERRED, INCLUDING THE IRO, THEN THE CAPT CONFERRED WITH SYS CTL AND MAINT CTL. IT WAS DECIDED TO RETURN TO EWR. QRH WAS REVIEWED, AND KEPT OPEN TO LOSS OF SYS 'A.' IN TERMINAL AREA (EWR) ENG #1 HYD PUMP LOW PRESSURE LIGHT CAME ON. THE QRH WAS CONSULTED, THE PUMP SWITCH WAS TURNED OFF PER THE CHKLIST. AN UNEVENTFUL LNDG WAS MADE WITH ALL SYS OPERATING NORMALLY EXCEPT FOR THE #1 ENG DRIVEN HYD PUMP OFF. HYD QUANTITY STABILIZED AT 25%. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE AIRPLANE WAS A B737-700. THE RPTR SAID THE CAUSE OF THE LOSS OF 'A' SYS HYD FLUID WAS A CHAFFED LINE IN THE L FLAP WELL JUST OUTBOARD OF THE MAIN WHEEL WELL.
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.