B767 crew reported a gradual loss of center system hydraulic quantity during last half of cruise flight. Crew made a reduced flap setting landing at destination after executing checklist procedures and consultations with maintenance.
Synopsis
B767 crew reported a gradual loss of center system hydraulic quantity during last half of cruise flight. Crew made a reduced flap setting landing at destination after executing checklist procedures and consultations with maintenance.
Narrative
Center Hydraulic Quantity. Approximately 30 mins into my crew rest within the second half of the duty period I was notified to come back to the flight deck to discuss an issue with the two Relief Pilots. This was an OE (Operating Experience) Qualification Line Check segment with the student as well on rest.Upon arrival on the flight deck I was informed of a leak in progress within the center hydraulic system at a rate of 1% per minute. At the time of the initial brief on the issue the quantity was approximately 64% and showing RF with no associated EICAS messages. I confirmed the loss rate while the two Relief Pilots reviewed the Hydraulic Quantity (HYD QTY-L (C; R) QRH procedures as well as in the event of total loss of quantity the (767) HYD SYS PRESS-C (Only) procedures with me. I concurred on the their assessment of needing to address the current quantity issue and preparing for the possibility of a total loss of Center quantity into a Center Pressure loss procedure.At this time I reassumed the left control seat and initiated a SAT call with dispatch and Maintenance Control. We gave an update on current conditions related to the center system and the aircraft overall. While Maintenance Control reviewed systems affected; a fact that we the flight crew had already reviewed; the loss rate continued. it was at the point I reminded the Maintenance Control we did not have time for his review due to the continued loss of fluid and were going to initial the HYD QTY-L(C;R) procedure for the center system despite not having the associated EICAS messages to retain what fluid remained. When asking Maintenance Control if there were other options the response was they would only point us to our procedures. No additional insights/procedures were offered by Maintenance Control. During this call it was also discussed we would continue to ZZZ Airport and not request priority handling just yet given operation of 2 system and no reliance on backup systems as well as the current QRH procedure not stating to land at nearest or similar verbiage. All concurred on assessment. Although we did state we will look at advising ATC once we were into domestic/arrival airspace due to possible loss of all quantity leading into the pressure QRH.Once off the SAT link; we executed the HYD QTY - C QRH procedure down to the deferred items. At this point the center quantity was at 58%. With the aircraft in a safe configuration for continued flight with little degradation to controls etc; I stepped back to the rest seat for about an additional hour to assure some rest. Instructions were given to monitor and advise if loss resumed and I then proceeded to brief the student who was in 1A. That discussion was his qualification line check was now incomplete due to the issues at hand and he would be assuming a relief pilot seat while I assigned the right control seat to one of the Relief Pilots given extensive experience in the aircraft and the possibly of a non-standard approach to landing. I also took the opportunity to do an initial brief with our Purser and gave instructions to pull his final service earlier to assure in seats 1:30 prior to estimated arrival.Upon that brief rest culmination I returned to the flight deck to assume the control seat and also alerted the student to return. At that point we still had 58% in the center position and in safe configuration for continued flight. The two Relief Pilots cycled to the lavatory and all then took appropriate seats.The plan was brief based upon the quantity QRH to execute a 15 mile final turning on the center system per the deferred items and then extend flaps/gear on associated flap speeds to try to protect the quantity dropping to zero and getting a subsequent pressure EICAS directing us to a second; more intensive; QRH procedure. We also reviewed as a crew the HYD SYS PRESS-C QRH in expectation we may get it if quantity would not hold. The principle operational difference between the two were approachflaps and speed (normal for the QTY QRH procedure; the other F20 VREF 20 for the PRESS procedure) as well as a alternate extension for gear and the flaps/slats once in the PRESS procedure. With all in concurrence with the 'game plan' I then briefed the Purser with additional details. The FAs (Flight Attendants) at this point were complete with final service and proceeding to secure for arrival at approx 1:45 from arrival. When transferred to ZZZ Center; we advised ATC and facilitated routing followed. At this time a passenger PA was made addressing a hydraulic system deficiency and we would continue to ZZZ airport and would keep them appraised of changes. Decision was also made to deactivate WiFi leveraging the instructions posed by our FOM but used to control information flow from aircraft that may hinder perspectives of current disposition and support of the flight and passenger.A second call was then made to Dispatch; Maintenance Control and then added the Chief Pilot prior to advising ATC. I reviewed the state of the aircraft; actions currently taken within the HYD QTY QRH and our decision to let ATC know as well as research options. We ruled out our initial alternate and looked at ZZZ1 airport (runways shorter than what we would like have seen) and then decided on ZZZ3 airport in the event our flaps/slats were not able to get to either our planned F25 approach under the QTY QRH or the F20VREF20 if needed in the PRESS QRH. There was some confusion explaining our current QRH for QTY allowed for normal operations versus the PRESS QRH dictating non-standard configurations. We settle on an estimate distance 5500-5700 needed for a F20VREF20 approach if ending up using the PRESS QRH. Although that would fit in ZZZ airport we determined less threat existed with longer surfaces in the event of other issues arising. The Chief Pilot concurred on our assessment. A final PA was made to the passengers to assure them of safe conditions and appreciation of their calmness and discretion.Once being vectored for ILS Runway XXL I noted the fuel quantity was approximately 14k. We had determined that 10.5 was our go point to ZZZ3 airport and our final reserve fuel was rounded up to 5K vs calculated 4.8k. At this point fuel was not becoming a consideration in planning and execution of procedures.At approximately 17 miles out while on an Intercept with a 'speed our discretion' clearance; F1 was called with the status page up to monitor C HYD QTY. We noted a significant hit to our QTY that was up to 63% at that time to approx 30%. With that information the decision was to drop gear while QTY and PRESS were still available. The gear did a normal extension but again took the QTY down to approx 15%. F5; F15; and F20 were all commanded while reducing airspeed. It was then; while on the localizer we saw the split flap/slat display and the system still at F1 settings. We also concurrently had the HYD PRESS C EICAS now displayed resulting in a forcing to that QRH. Actions were then taken IAW (In Accordance With) the QRH but in a hurried fashion given now descending below 3000 ft LOC and GS. Ground Prox Overide was pushed; ALT Flaps/Slats armed; and ALT selector set to F20. No response was noted for the next few minutes and a decision was made to execute a level off and missed approach.The relief pilot now operating the aircraft hand flew a level off while MCP (Mode Control Panel) was reset to disconnect from the GS/LOC. Vectors were made to the west. We re-accomplished the tasks in the PRESS QRH to no avail on movement of the flaps/slats. I then decided to take the flap handle from the F20 position; pick it up out of the detention; then re-affirm it back into the detention. It was at this point the flaps began the movement to F20. We reconfirmed speeds/gear/flaps and commenced an intercept of both LOC/GS.At around 1500 ft agl I reviewed with the right seat the F20 picture out the window differences and airspeed/float that could be expected.A normal approach to landing was made favoring a slightly low GS to attempt to maximize runway availability. A slight float occurred but touchdown was made within the zone. We executed full reverse and manual braking holding reverse longer that standard to assure stabilized tracking since nose wheel steering may be affected. We stopped just before Taxiway 1 on XXL. During the rollout the student was instructed to countdown the last 4k of runway to assure awareness and the second Relief Pilot in the middle JS (Jump Seat) was backing up awareness of systems operation. At this time fuel was approximately 10.3 that correlated with our go ZZZ3 airport decision point. Of note during the GA procedure the gear was not/could not be retracted due to the PRESS situation. Burn was above 15-16k during the re-vectoring when level. Upon stopping I held the brakes vice setting while fire rescue inspected and established communications. Decision was made to remain on runway due to brake temps possibly needing addressed by fire rescue and the possibility of not having/losing NG steering. Maximum brake temp culminated at 4.1 on wheel #1 with wheel #3 next at 3.8. No temps above those were noted. Fire rescue checked aircraft and found no fires or deflation of tires. At that point we executed the after landing but left the flaps down in the event of an evacuation being needed for unforeseen reasons. Once tug was on site we execute the tow procedure then relived control to the tug driver and pulled safely into the gate. During these process appropriate call were made to FAs; passengers; and other entities.We arrived at the gate and executed the parking checklist; executed an extensive debrief where we found our CRM to be essential to this safe outcome. I then instructed the student and non-control seat Relief Pilot to take hat and jacket and assure the passenger saw them as they deplaned.Several departments came onto aircraft for a quick inject. We then left the flight deck and debriefed the FAs thanking them for their coordination/synchronization and outstanding efforts.
Second reporter narrative
Approximately 30 mins after the Captain and trainee FO went on their break we noticed a slowly decreasing center hydraulic quantity at a rate of 1% per minute. At the time of the initial brief on the issue the quantity was approximately 64% and showing RF with no associated EICAS messages. The other FO and I agreed that this was a critical issue; and we called the Captain back to the flight deck while reviewing pertinent checklists and systems. Upon his return we all confirmed the loss rate and we reviewed the Hydraulic Quantity (HYD QTY-L (C; R) QRH procedures as well as in the event of total loss of quantity the (767) HYD SYS PRESS-C (Only) procedures with the Captain; who concurred on the our assessment of needing to address the current quantity issue and preparing for the possibility of a total loss of Center quantity into a Center Pressure loss procedure.At this time the Captain reassumed the left control seat and initiated a SAT call with dispatch and Maintenance Control. We gave an update on current conditions related to the center system and the aircraft overall. While Maintenance Control reviewed systems affected; a fact that we the flight crew had already reviewed; the loss rate continued. it was at the point the Captain reminded Maintenance Control we did not have time for his review due to the continued loss of fluid and were going to initial the HYD QTY-L(C;R) procedure for the center system despite not having the associated EICAS messages to retain what fluid remained. When asking Maintenance Control if there were other options the response was they would only point us to our procedures. No additional insights/procedures were offered by Maintenance Control. During this call it was also discussed we would continue to ZZZ airport and advise ATC just yet; given normal operation of the other 2 systems and no reliance on backup systems as well as the current QRH procedure not stating to land at nearest or similar verbiage. All concurred on assessment; although we did state we will look at notifying ATC once we were into domestic/arrival airspace due to possible loss of all quantity leading into the pressure QRH.Once off the SAT link; we executed the HYD QTY - C QRH procedure down to the deferred items. By turning off all center system pumps; the pressure went to zero and the quantity stopped decreasing; as we expected. At this point the center quantity was at 58%. With the aircraft in a safe configuration for continued flight with little degradation to controls etc; the Captain stepped back to the rest seat for about an additional hour to assure some rest. Instructions were given by him for us to monitor and advise if loss resumed and then proceeded to brief the student who was in 1A. That discussion was his qualification line check was now incomplete due to the issues at hand and he would be assuming a relief pilot seat while the Captain assigned the right control seat to one of the Relief Pilots given extensive experience in the aircraft and the possibly of a non-standard approach to landing. The Captain also took the opportunity to do an initial Brief with our Purser and gave instructions to pull his final service earlier to assure in seats 1:30 prior to estimated arrival.Upon that brief rest culmination the Captain returned to the flight deck to assume the control seat and also alerted the student to return. At that point we still had 58% in the center position and in safe configuration for continued flight. We two Relief Pilots cycled to the lavatory and all then took appropriate seats.The plan was briefed based upon the quantity QRH to execute a 15 mile final turning on the center system per the deferred items and then extend flaps/gear on associated flap speeds to try to protect the quantity dropping to zero and getting a subsequent pressure EICAS directing us to a second; more intensive; QRH procedure. We also reviewed as a crew the HYD SYS PRESS-C QRH in expectation we may get it if quantity would nothold. The principle operational difference between the two were approach flaps and speed (normal for the QTY QRH procedure; the other F20 VREF 20 for the PRESS procedure) as well as a alternate extension for gear and the flaps/slats once in the PRESS procedure. With all in concurrence with the 'game plan' the Captain then briefed the Purser with additional details. The FAs (Flight Attendants) at this point were complete with final service and proceeding to secure for arrival at approx 1:45 from arrival.When transferred to ZZZ Center; an ATC was advised and facilitated routing followed. At this time a passenger PA was made addressing a hydraulic system deficiency and we would continue to ZZZ airport and would keep them appraised of changes. Decision was also made to deactivate WiFi leveraging the instructions posed by our FOM but used to control information flow from aircraft that may hinder perspectives of current disposition and support of the flight and passenger.A second call was then made to Dispatch; Maintenance Control and then added the Chief Pilot prior to advising ATC. The Captain reviewed the state of the aircraft; actions currently taken within the HYD QTY QRH and our decision to advised ATC as well as research options. We ruled out our initial alternate and looked at ZZZ1 airport (runways shorter than what we would like have seen) and then decided on ZZZ2 airport in the event our flaps/slats were not able to get to either our planned F25 approach under the QTY QRH or the F20VREF20 if needed in the PRESS QRH. There was some confusion explaining our current QRH for QTY allowed for normal operations versus the PRESS QRH dictating non-standard configurations. We settled on an estimated distance 5500-5700 needed for a F20VREF20 approach if ending up using the PRESS QRH. Although that would fit in ZZZ airport we determined less threat existed with longer surfaces in the event of other issues arising. The Chief Pilot concurred on our assessment. A final PA was made to the passengers to assure them of safe conditions and appreciation of their calmness and discretion.Once being vectored for ILS Runway XXL we noted the fuel quantity was approximately 14k. We had determined that 10.5 was our go point to ZZZ2 airport and our final reserve fuel was rounded up to 5K vs calculated 4.8k. At this point fuel was not becoming a consideration in planning and execution of procedures.At approximately 17 miles out while on an Intercept with a 'speed out discretion' clearance; as pilot flying; I called for Flaps 1 with the status page up to monitor C HYD QTY. We noted a significant hit to our QTY that was up to 63% at that time to approx 30%. With that information the decision was to drop gear while QTY and PRESS were still available. The gear did a normal extension but again took the QTY down to approx 15%. F5; F15; and F20 were all commanded while reducing airspeed. It was then; while on the localizer we saw the split flap/slat display and the system still at F1 settings. We also concurrently had the HYD PRESS C EICAS now displayed resulting in a forcing to that QRH. Actions were then taken IAW (In accourdance with) the QRH but in a hurried fashion given now descending below 3000 ft LOC and GS. Ground Prox Override was pushed; ALT Flaps/Slats armed; and ALT selector set to F20. No response was noted for the next few minutes and I advocated for and the Captain agreed that a go-around was our best course of action; as we did not have performance for a flaps 1 (or less) landing; so the decision was made to execute a level off and missed approach.As PF; I executed a 'soft go-around' and hand flew a level off (without hitting the GA Switch; which would have just added to the confusion and degraded safety at that point) while the MCP (Mode Control Panel) was reset to disconnect from the GS/LOC. Vectors were made to the west. We re-accomplished the tasks in the PRESS QRH to no avail on movement of the flaps/slats. The Captain then decided to take the flap handle from the F20 position; pick it up out of the detention; then re-affirm it back into the detention. It was at this point the flaps began the movement to F20. We reconfirmed speeds/gear/flaps and commenced an intercept of both LOC/GS.At around 1500 ft agl the Captain reviewed with me the F20 sight picture differences and airspeed/float that could be expected. A normal approach to landing was made favoring a slightly low GS to attempt to maximize runway availability. A slight float occurred but touchdown was made within the first 1000 ft zone. We executed full reverse and manual braking holding reverse longer that standard to assure stabilized tracking since nose wheel steering may be affected. We stopped just before taxiway 1 on Runway XXL. During the rollout the student was instructed to countdown the last 4k of runway to assure awareness and the second Relief Pilot in the middle JS (Jump Seat) was backing up awareness of systems operation. At this time fuel was approximately 10.3 that correlated with our go ZZZ2 airport decision point. Of note during the GA procedure the gear was not/could not be retracted due to the PRESS situation. Burn was above 15-16k during the re-vectoring when level.Upon stopping the Captain held the brakes instead of setting them while fire rescue inspected and established communications. Decision was made to remain on runway due to brake temps possibly needing addressed by fire rescue and the possibility of not having/losing NG steering. Maximum brake temp culminated at 4.1 on wheel #1 with wheel #3 next at 3.8. No temps above those were noted. Fire rescue checked aircraft and found no fires or deflation of tires. At that point we executed the after landing but left the flaps down in the event of an evacuation being needed for unforeseen reasons. Once tug was on site we execute the tow procedure then relived control to the tug driver and pulled safely into the gate. During these process appropriate call were made to FAs; passengers; and other entities.We arrived at the gate and executed the parking checklist; executed an extensive debrief where we found our CRM to be essential to this safe outcome. The Captain then instructed the student and non-control seat Relief Pilot to take hat and jacket and assure the passenger saw them as they deplaned.Several departments came onto aircraft for a quick deberief. We then left the flight deck and debriefed the FAs thanking them for their coordination/synchronization and outstanding efforts.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.