Date: 202008
Flight conditions: VMC
Light: Dusk
Aircraft: B787 Dreamliner Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Airspace: Class B ZZZ
Aircraft component: Engine Air Starter
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Human factors: Fatigue; Troubleshooting; Communication Breakdown
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Aircraft In Service At Gate
Result: General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Human Factors; Procedure; MEL; Aircraft
Primary problem: MEL

Narrative: Upon pushing back we encountered what we believed to be a start valve would not open problem on the #1 engine. We proceeded to run the appropriate checklist which required the mechanic to manually open the start valve. The procedure proved unsuccessful and we executed a BTB. Upon trouble shooting; maintenance was able to get the engine started pretty quickly and applied MEL. After talking with the mechanic and reviewing the MEL we decided we were going to start the #1 engine before we pushed back. The mechanic talked about pressing and holding the start valve switch while the engine was starting. I told him I was uncomfortable with that because that is not what was in our QRH. We had a discussion as to whether it meant press and hold or just press the switch. I came to the conclusion that it meant press only not hold and if that did not work something else is the problem. I did not want to do a procedure that is not in our QRH. The mechanics conclusion was the engine was not going to start correctly unless I pressed and held the start switch. After more discussion we saw the Arm Light or Start switch failure checklist which was exactly what we had. Our start switch was not latching when selected. I was very happy at the time because it was a QRH procedure to start the engine in the state that it was in. What did not dawn on me in that particular second was that it was a different MEL. Same overall outcome; just a different procedure to start the engine. The MEL should have been a different one. I realized that maintenance was going to have difficulty trouble shooting the problem and I did not want another crew to go out to the aircraft and apply the wrong procedure. Upon landing I put a comment in the logbook about using the Start switch failure procedure in order to help maintenance quickly trouble shoot the problem. After reviewing that checklist I realize that was not correct because it would need to be deferred prior to departure. It was our third leg of a night that started late the previous day. Fatigue was definitely becoming an issue. The initial problem was myself misdiagnosing the problem and sending everyone down the wrong rabbit hole with the start valve fails to open checklist. If I would have diagnosed that correctly we would have ran the checklist and received our deferral and been on our way. This also helped lead the mechanic to that deferral. I had the First Officer run the secure checklist so we could go inside and get out of maintenances way. We were not expecting maintenance to correct the issue that quickly and were caught a little off guard. You can imagine my surprise when they turned the engine and got it started so quickly. We reviewed the MEL just like we were supposed to and had to setup the cockpit to get ready to fly again. We had to review all our performance; get an ARTR and make sure our flight planning was still good. Sometime between the long discussion of how we were going to start the engine and what procedure I was going use; I lost track of the fact of this may be an incorrect MEL deferral we are using. I was correct in being alarmed by not starting the engine with the correct checklist procedure; but failed to go back and make sure everything was correct when I found the right answer. I was more focused on the fact of I saw the procedure in the QRH and it was exactly what the mechanic was telling me what needed to do get the engine started. I do not believe anything was procedurally done incorrectly other than the paperwork issue. The only reason why I entered a comment in the logbook was to help lead maintenance down the correct path. I talked to the mechanics upon landing and made sure they new the situation. I realized after the fact that the comment wasn't appropriate because it would have required a deferral and never should be entered as a comment. The aircraft never was returned to a normal status by running the QRH checklist. The First Officer did an outstanding job of helping meand looking up checklists and MEL's. Maintenance did an outstanding job of trouble shooting quickly. I think the lesson learned is to just realize when something does not seem quite right it probably isn't. And when that happens you probably should start all over again to assure that it is done correctly.




Synopsis: Captain reported fatigue and confusion resulted in a delay due to misapplication of an MEL.