Narrative:

Right hydraulic light came on in-flight (low pressure). Right hydraulic gauge failed to off-scale high reading. Referred to in-flight QRH procedure for air carrier medium large transport and checklist does not contain a procedure for low pressure and abnormal high quantity indication. Attempted hydraulic pressure low and quantity normal checklist, placed right engine to high (no pressure). Rudder manual control light came on at this point and as we had no reliable quantity indication, we entered checklist for hydraulic quantity and pressure low as we felt fluid was depleted and did not want to damage pumps by trial and error trouble- shooting. My thoughts at time were to notify dispatch of problem, let flight attendants know we were going to rdu. Prepared aircraft for worst case (hydraulic low and quantity low), land at rdu versus fay for crash rescue/maintenance. In short, a lot was going on here. We accomplished checklist, declared emergency and landed normally for loss of right system. Gear was pinned after landing and taxied to gate. This sequence of events could have been made better by turning on the right auxiliary pump even though the checklist does not say to do this for pressure low and quantity high. The problem is that our procedures are incomplete and assume you will 'play' with all associated switches, even though the status of the system is unknown. This is not prudent. You could aggravate certain hydraulic failures by doing this, i.e., large leaks. Specifically, all operators should be aware that quantity gauge goes off scale high whenever pressure is lost at altitude (by leak or pump failure). Our procedure should say: hydraulic pressure low and quantity normal/high, instead of hydraulic pressure low and quantity normal. Then you have a place to enter checklist and don't have to guess what to do. Airworthiness directive should be issued. Will prevent gear door skid usage on landing.

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Original NASA ASRS Text

Title: LGT ACR ACFT'S HYD SYS FAILED RESULTING IN AN EMER DECLARED AND LNDG.

Narrative: R HYD LIGHT CAME ON INFLT (LOW PRESSURE). R HYD GAUGE FAILED TO OFF-SCALE HIGH READING. REFERRED TO INFLT QRH PROC FOR ACR MLG AND CHKLIST DOES NOT CONTAIN A PROC FOR LOW PRESSURE AND ABNORMAL HIGH QUANTITY INDICATION. ATTEMPTED HYD PRESSURE LOW AND QUANTITY NORMAL CHKLIST, PLACED R ENG TO HIGH (NO PRESSURE). RUDDER MANUAL CTL LIGHT CAME ON AT THIS POINT AND AS WE HAD NO RELIABLE QUANTITY INDICATION, WE ENTERED CHKLIST FOR HYD QUANTITY AND PRESSURE LOW AS WE FELT FLUID WAS DEPLETED AND DID NOT WANT TO DAMAGE PUMPS BY TRIAL AND ERROR TROUBLE- SHOOTING. MY THOUGHTS AT TIME WERE TO NOTIFY DISPATCH OF PROB, LET FLT ATTENDANTS KNOW WE WERE GOING TO RDU. PREPARED ACFT FOR WORST CASE (HYD LOW AND QUANTITY LOW), LAND AT RDU VERSUS FAY FOR CRASH RESCUE/MAINT. IN SHORT, A LOT WAS GOING ON HERE. WE ACCOMPLISHED CHKLIST, DECLARED EMER AND LANDED NORMALLY FOR LOSS OF R SYS. GEAR WAS PINNED AFTER LNDG AND TAXIED TO GATE. THIS SEQUENCE OF EVENTS COULD HAVE BEEN MADE BETTER BY TURNING ON THE R AUX PUMP EVEN THOUGH THE CHKLIST DOES NOT SAY TO DO THIS FOR PRESSURE LOW AND QUANTITY HIGH. THE PROB IS THAT OUR PROCS ARE INCOMPLETE AND ASSUME YOU WILL 'PLAY' WITH ALL ASSOCIATED SWITCHES, EVEN THOUGH THE STATUS OF THE SYS IS UNKNOWN. THIS IS NOT PRUDENT. YOU COULD AGGRAVATE CERTAIN HYD FAILURES BY DOING THIS, I.E., LARGE LEAKS. SPECIFICALLY, ALL OPERATORS SHOULD BE AWARE THAT QUANTITY GAUGE GOES OFF SCALE HIGH WHENEVER PRESSURE IS LOST AT ALT (BY LEAK OR PUMP FAILURE). OUR PROC SHOULD SAY: HYD PRESSURE LOW AND QUANTITY NORMAL/HIGH, INSTEAD OF HYD PRESSURE LOW AND QUANTITY NORMAL. THEN YOU HAVE A PLACE TO ENTER CHKLIST AND DON'T HAVE TO GUESS WHAT TO DO. AIRWORTHINESS DIRECTIVE SHOULD BE ISSUED. WILL PREVENT GEAR DOOR SKID USAGE ON LNDG.

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.