Narrative:

Hydraulic caution light illuminated while taxiing to runway 3C at taxiway K and taxiway K15. I began required procedures and completed the QRH checklist. The captain contacted maintenance and requested a tow back to the gate. We both were applying pressure to the brakes. I began to make an announcement to the passenger when the aircraft began to move. The captain began to shut the engine down. The aircraft began to yaw to the left. The captain applied differential power and reverse. The aircraft would not stop. When it was clear we had no brakes to stop the plane, the captain immediately shut both engines down. We rolled to a stop in the grass. All passenger were safe, crew was safe. ATC and maintenance were notified. A very poorly written QRH emergency checklist, I believe, should be modified and improved. Callback conversation with reporter revealed the following information: reporter stated that, after hydraulic caution light came on, captain noticed braking action was degrading, so reporter began to assist in application of brakes. Reporter went through the QRH checklist. In completing checklist procedure, the electric hydraulic pump was turned off. Aircraft began to move. Reporter stated turning hydraulic pump back on did not help, so captain began shutting down engines, left engine first. Aircraft continued moving, yawing to left. Differential reverse thrust did not stop aircraft, so captain shut down second engine. Aircraft stopped. Reporter admits crew did not employ the manual hydraulic pump. Reporter's contention that checklist is ambiguous is based on her observation, apparently concurred with by reporter's chief pilot, that the checklist is for use in-flight, not on the ground. She had no suggestions as to how the checklist could be improved. Reporter also feels that saab 340A's single hydraulic system, with no backup, is reflection of poor design. Reporter stated that, although her chief pilot agreed with her contention that the checklist was not applicable to a hydraulic failure/problem while taxiing, no changes to the checklist have been made in the 2 months since the incident occurred.

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Original NASA ASRS Text

Title: AN SF340A HYD SYS FAILURE WHILE TAXIING LED TO LOSS OF ACFT CTL WHICH IN TURN RESULTED IN TXWY EXCURSION.

Narrative: HYD CAUTION LIGHT ILLUMINATED WHILE TAXIING TO RWY 3C AT TXWY K AND TXWY K15. I BEGAN REQUIRED PROCS AND COMPLETED THE QRH CHKLIST. THE CAPT CONTACTED MAINT AND REQUESTED A TOW BACK TO THE GATE. WE BOTH WERE APPLYING PRESSURE TO THE BRAKES. I BEGAN TO MAKE AN ANNOUNCEMENT TO THE PAX WHEN THE ACFT BEGAN TO MOVE. THE CAPT BEGAN TO SHUT THE ENG DOWN. THE ACFT BEGAN TO YAW TO THE L. THE CAPT APPLIED DIFFERENTIAL PWR AND REVERSE. THE ACFT WOULD NOT STOP. WHEN IT WAS CLR WE HAD NO BRAKES TO STOP THE PLANE, THE CAPT IMMEDIATELY SHUT BOTH ENGS DOWN. WE ROLLED TO A STOP IN THE GRASS. ALL PAX WERE SAFE, CREW WAS SAFE. ATC AND MAINT WERE NOTIFIED. A VERY POORLY WRITTEN QRH EMER CHKLIST, I BELIEVE, SHOULD BE MODIFIED AND IMPROVED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT, AFTER HYD CAUTION LIGHT CAME ON, CAPT NOTICED BRAKING ACTION WAS DEGRADING, SO RPTR BEGAN TO ASSIST IN APPLICATION OF BRAKES. RPTR WENT THROUGH THE QRH CHKLIST. IN COMPLETING CHKLIST PROC, THE ELECTRIC HYD PUMP WAS TURNED OFF. ACFT BEGAN TO MOVE. RPTR STATED TURNING HYD PUMP BACK ON DID NOT HELP, SO CAPT BEGAN SHUTTING DOWN ENGS, L ENG FIRST. ACFT CONTINUED MOVING, YAWING TO L. DIFFERENTIAL REVERSE THRUST DID NOT STOP ACFT, SO CAPT SHUT DOWN SECOND ENG. ACFT STOPPED. RPTR ADMITS CREW DID NOT EMPLOY THE MANUAL HYD PUMP. RPTR'S CONTENTION THAT CHKLIST IS AMBIGUOUS IS BASED ON HER OBSERVATION, APPARENTLY CONCURRED WITH BY RPTR'S CHIEF PLT, THAT THE CHKLIST IS FOR USE INFLT, NOT ON THE GND. SHE HAD NO SUGGESTIONS AS TO HOW THE CHKLIST COULD BE IMPROVED. RPTR ALSO FEELS THAT SAAB 340A'S SINGLE HYD SYS, WITH NO BACKUP, IS REFLECTION OF POOR DESIGN. RPTR STATED THAT, ALTHOUGH HER CHIEF PLT AGREED WITH HER CONTENTION THAT THE CHKLIST WAS NOT APPLICABLE TO A HYD FAILURE/PROB WHILE TAXIING, NO CHANGES TO THE CHKLIST HAVE BEEN MADE IN THE 2 MONTHS SINCE THE INCIDENT OCCURRED.

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.