Narrative:

Approximately half way into flight I noticed a status advisory message after returning from my break that the flight data recorded had a minor malfunction. At the same time I noticed a RF indication for the left hydraulic quantity indication and that the level was .74; the status of the RF indication fluctuated between 1.02 and .71 for a brief period and maintained .71 for approach. The crew discussed systems lost in case of loss of fluid and monitored for remainder of flight. These systems included flaps/ slats; hydraulic gear operation; nose wheel steering and hmg. Approach briefing was for ZZZ with visual backup and auto brakes 3 for the 7;700 ft long runway at 134K landing weight. Noted terrain peaks approximately 5 miles from departure end of runway with peak alt at nearly 3;000 ft AGL. While maneuvering for the approach level at 2;500 ft while on vectors to final approach aircraft was configured at flaps 15. I called for gear down flaps 20 landing checklist. Flaps went to 20 gear went to down position and before we completed landing checklist I called for flaps 30 landing checklist. The EICAS and master caution alerted us that we had a flap disagreement message. Flaps were at 20 indicated. We also noted the landing gear light was illuminated on gear doors with 3 green lights. We maintained 2;500 ft past FAF and continued inbound towards runway at ATC direction until vectored for missed approach and maintained 2;500 ft. Fuel at that time was (8.5 KG). We proceeded to accomplish the QRH procedures for flap disagreement before retracting gear. QRH indicated a flaps 20 approach and landing and missed approach would have to be at flaps 20 as secondary message flap lockout. We contacted dispatch and discussed situation with dispatcher and contacted maintenance control. When we researched landing distance tables jointly with dispatcher 7;900 ft seemed to be distance to safely operate the aircraft although actual distance needed was less (approximately 3;700). A joint decision between all 3 crew; dispatch; and maintenance control was that a nearby larger airport was a better option due to available runway length; aircraft amenities and lack of terrain combined with better crash fire and rescue and more accessibility to parts for repair. We coordinated with dispatch diversion to the larger airport and discussed declaring an emergency as flaps 20 is not a normal flap landing configuration and slats would also be only at approach configuration and normal data for all those runways was only for flaps 25 or flaps 30. Dispatcher gave us confirmation on diversion and declaration of emergency via joint operation control and gave us time and initials. We coordinated with local control on diversion and were given instructions to climb to 8;000 and contact approach where we declared emergency and coordinated landing on longest runway and landed using about 7;000 ft of available runway with auto brakes set to 3. We proceeded to taxi and monitored brakes - peak brake temperature was 6 on two tires and 5 on 3 more. Landing fuel was 5.2 KG. I feel this was an excellent example of the training our pilots; dispatchers and flight attendants received in CRM and crew coordination using all available resources. It was textbook!after touchdown there was some discussion about why we diverted and why we didn't land the aircraft as the book indicated we could have landed in 3;700 ft. This figure to me is only if I have no other options available at that time! One suggestion would be to have tables in QRH for actual landing distance tables to be included in the flap asymmetry and flap disagree abnormal procedures section of QRH so data is readily available as part of procedure similar to airbus! Our training in these situations has always been to take the longest available runway declare and emergency and to prepare the cabin; to contact dispatch and maintenance control and coordinate. Our training also is to break off approach if malfunction occurs and there is not enough time to accomplish checklist and to check all available data for safety margins. Fuel was also a consideration as we started with an additional 1 KG and flight plan called for us to land at destination with 10.0 KG without the additional 1.0 and en-route burn was 2.5 greater than planned. Plus we had already executed one missed approach; in the unlikely event of another missed approach with possible diversion would have left us about 2.0 KG landing fuel well below safety margins. All this was done in accordance with our training standards and to take the most conservative approach. Yes the aircraft could have stopped in 3;700 ft per the book but would have to been at risk of blowing tires and disabling the aircraft on the runway and leading to a possible evacuation. It is the judgment of this entire flight crew and dispatcher that all operational safety standards were met or exceeded and that no additional maintenance was required for the aircraft to depart on the final leg after only a brief interruption of service and diagnosis.

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Original NASA ASRS Text

Title: B757 Captain experiences a left hydraulic system failure during approach and elects to divert to an airport with a longer runway. The landing gear is down with the doors open and the flaps are at 20 and locked. An emergency is declared and an uneventful landing and taxi in ensues.

Narrative: Approximately half way into flight I noticed a status advisory message after returning from my break that the flight data recorded had a minor malfunction. At the same time I noticed a RF indication for the left hydraulic quantity indication and that the level was .74; the status of the RF indication fluctuated between 1.02 and .71 for a brief period and maintained .71 for approach. The crew discussed systems lost in case of loss of fluid and monitored for remainder of flight. These systems included flaps/ slats; hydraulic gear operation; nose wheel steering and HMG. Approach briefing was for ZZZ with visual backup and auto brakes 3 for the 7;700 FT long runway at 134K landing weight. Noted terrain peaks approximately 5 miles from departure end of runway with peak alt at nearly 3;000 FT AGL. While maneuvering for the approach level at 2;500 FT while on vectors to final approach aircraft was configured at flaps 15. I called for gear down flaps 20 Landing Checklist. Flaps went to 20 gear went to down position and before we completed landing checklist I called for flaps 30 Landing Checklist. The EICAS and Master caution alerted us that we had a flap disagreement message. Flaps were at 20 indicated. We also noted the landing gear light was illuminated on gear doors with 3 green lights. We maintained 2;500 FT past FAF and continued inbound towards runway at ATC direction until vectored for missed approach and maintained 2;500 FT. Fuel at that time was (8.5 KG). We proceeded to accomplish the QRH procedures for flap disagreement before retracting gear. QRH indicated a flaps 20 approach and landing and missed approach would have to be at flaps 20 as secondary message flap lockout. We contacted Dispatch and discussed situation with Dispatcher and contacted Maintenance Control. When we researched landing distance tables jointly with Dispatcher 7;900 FT seemed to be distance to safely operate the aircraft although actual distance needed was less (approximately 3;700). A joint decision between all 3 crew; Dispatch; and Maintenance Control was that a nearby larger airport was a better option due to available runway length; aircraft amenities and lack of terrain combined with better crash fire and rescue and more accessibility to parts for repair. We coordinated with Dispatch diversion to the larger airport and discussed declaring an emergency as flaps 20 is not a normal flap landing configuration and slats would also be only at approach configuration and normal data for all those runways was only for flaps 25 or flaps 30. Dispatcher gave us confirmation on diversion and declaration of emergency via joint operation control and gave us time and initials. We coordinated with Local Control on diversion and were given instructions to climb to 8;000 and Contact Approach where we declared emergency and coordinated landing on longest runway and landed using about 7;000 FT of available runway with auto brakes set to 3. We proceeded to taxi and monitored brakes - peak brake temperature was 6 on two tires and 5 on 3 more. Landing fuel was 5.2 KG. I feel this was an excellent example of the training our pilots; dispatchers and flight attendants received in CRM and crew coordination using all available resources. It was textbook!After touchdown there was some discussion about why we diverted and why we didn't land the aircraft as the book indicated we could have landed in 3;700 FT. This figure to me is only if I have no other options available at that time! One suggestion would be to have tables in QRH for actual landing distance tables to be included in the flap asymmetry and flap disagree abnormal procedures section of QRH so data is readily available as part of procedure similar to Airbus! Our training in these situations has always been to take the longest available runway declare and emergency and to prepare the cabin; to contact Dispatch and Maintenance Control and coordinate. Our training also is to break off approach if malfunction occurs and there is not enough time to accomplish checklist and to check all available data for safety margins. Fuel was also a consideration as we started with an additional 1 KG and flight plan called for us to land at destination with 10.0 KG without the additional 1.0 and en-route burn was 2.5 greater than planned. Plus we had already executed one missed approach; in the unlikely event of another missed approach with possible diversion would have left us about 2.0 KG landing fuel well below safety margins. All this was done in accordance with our training standards and to take the most conservative approach. Yes the aircraft could have stopped in 3;700 FT per the book but would have to been at risk of blowing tires and disabling the aircraft on the runway and leading to a possible evacuation. It is the judgment of this entire flight crew and Dispatcher that all operational safety standards were met or exceeded and that no additional maintenance was required for the aircraft to depart on the final leg after only a brief interruption of service and diagnosis.

Data retrieved from NASA's ASRS site as of April 2012 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.