Flight crew reported confusion during QRH procedures for a hydraulic system low quantity event. This led to an unnecessary manual extension of the landing gear; complicating the landing at destination airport.
Synopsis
Flight crew reported confusion during QRH procedures for a hydraulic system low quantity event. This led to an unnecessary manual extension of the landing gear; complicating the landing at destination airport.
Narrative
While on the arrival into ZZZ; passing through approximately 12;000 feet; we had an EICAS (Engine Indicating and Crew Alerting System) advisory message 'HYD SYS 1 LO QTY' appear after ATC issued a runway change. The captain advised me to run the HYD SYS 1 LO QTY QRH. We noted that our hydraulic quantity on system 1 was in the amber range. I proceeded to run the applicable checklist while the captain took over the radios and maintained control of the aircraft. Before completing the 'HYD SYS 1 LO QTY' quick reference handbook procedure; it included HYD SYS 1 FAIL procedure to be followed 'as required' I should have noticed that if 'HYD SYS FAIL' EICAS messages were displayed-- the procedure WOULD be required. I was thinking that because our hydraulic quantity was low; we might have a system degradation based on what I read in the HYD SYS 1 FAIL QRH; and that it was required. I subsequently followed the HYD SYS 1 FAIL QRH and did not see the HYD SYS 1 FAIL EICAS messages that corresponded to the HYD SYS 1 FAIL QRH. I reviewed the entire HYD SYS 1 FAIL QRH procedure once verbally all the way through with minor interruptions; and proceeded to review it two more times verbally; only highlighting the gear extension and degradation information. In error; we then proceeded to execute the HYD SYS 1 FAIL QRH which resulted in a manual gear extension. We took all of the precautions per the QRH that some aircraft systems may be degraded and completed the HYD SYS 1 FAIL QRH and landed. After landing the Captain and I debriefed the event where we read back through both of the QRH procedures that we had followed and then we realized that we could likely have closely monitored the applicable hydraulic systems and dropped the landing gear early and that HYD 1 LO QTY was not a trigger for the HYD SYS 1 fail QRH. Overall I felt that communication was high; but I failed to confirm that the EICAS messages for the HYD SYS 1 FAIL QRH were displayed; which might have changed our course of action. I believe that had I compared the messages only for the HYD SYS 1 FAIL that were not present on our aircraft then; the 'As required' statement in the HYD 1 LO QTY QRH would have been more apparent to me. CRM was used throughout the entire flight including the emergency; but I could have done a better job at highlighting that the EICAS messages for the HYD 1 SYS FAIL were not present. I made an assumption when reading the QRH that though we didn't have a hydraulic system 1 failure indication; our lack of hydraulic quantity could lead to a degradation in hydraulic systems and made the HYD SYS 1 FAIL QRH required. This was not the case; I will make more emphasis in verifying the EICAS messages for the applicable QRH in order to achieve a higher level of CRM.
Second reporter narrative
On descent in the later part of the STAR into ZZZ the HYD 1 LOW QTY advisory was displayed on the EICAS (Engine Indicating and Crew Alerting System). The HYD 1 sys was in the amber. After handling a late runway change the QRH was executed for HYD 1 LOW QTY; which at the end says to execute the HYD 1 FAIL QRH procedure 'as required'. This was misinterpreted as being told to act as though we were having a HYD 1 SYS failure. In hind sight it became clear that the HYD 1 SYS failure X of the QRH should not have been executed due to the fact that the trigger of having the 'HYD 1 FAIL' had not yet been explicitly displayed on the EICAS. Somehow in error this trigger was overlooked and a manual gear extension was conducted along with the assumption we would have several systems inop. In hind sight the most likely outcome had this not been overlooked would have been an attempt to lower the gear early and the system would simply be 'monitored' unless that failure EICAS was displayed in flight- as well as an emergency not being declared in that case (rather just heightened awareness of that situation and the implications).In hind sight I'm not sure how the HYD 1 FAIL requirement was overlooked. CRM was ideal overall and it may have come down to QRH assumptions or an interruption at that critical point of EICAS confirmation. As mentioned; it was interpreted in part as though the QRH was driving to act as though the system was failed or imminently going to be failed. Possibly to avoid this in the future extra emphasis should be on not only confirming the correct checklist but just as importantly the presence or the absence of the EICAS message triggers for QRH portions. Both crew in the debrief realized the QRH was incorrectly executed.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.