B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 112
Confusion
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented
Human Factors; Manuals; Company Policy
It was my leg. Preflight activities had been normal and we were not rushed at all. We blocked out four minutes early and were taxiing southbound on Taxiway X for takeoff on Runway XXR at Taxiway Y. We had been instructed to hold short of Runway XXR at Taxiway Y and were almost stopped. I had already called for the Before Takeoff Checklist and the FO challenged me with 'start levers' at the next to last step in that checklist. I reached down to confirm 'idle.' My practice has been to hold the start levers with my thumb and forefinger; confirm the idle detent position with a slight nudge forward and a slight nudge rearward; then to respond; 'idle.' However this time with the slight nudge to the rear; the number one start lever felt like it was not quite fully down in the idle detent and it came up over the edge; and I unintentionally shut down the number one engine. I was surprised and stunned. I announced the situation to the FO and set the parking brake. Then; instinctively I reached down again to confirm the start lever positions. At that point; I must have 'matched' the start lever heights; and to my horror; when I nudged the levers rearward again; I unintentionally shut down the number two engine as well. Now clearly in the Red; I announced this new situation. I started the APU and put electrical power back on the aircraft. We told ATC that we had a problem and that it would be a few minutes before we could move. Feeling completely inept and embarrassed; I told the FO that we would start over and reaccomplish everything beginning with the Before Start Checklist. The FO agreed. Then very deliberately and methodically we reaccomplished our takeoff preparations; to include all flows and checklists beginning with the Before Start Checklist. After assuring all systems were operating normally and checklists were complete; we briefly discussed and sensed that our risk assessment procedures had already served us well in returning the aircraft to its normal/usual condition as well as mitigating the risk of the additive condition we had just experienced. We would still use it to mitigate the new (Crew factor) risk introduced by my extreme frustration with myself. The FO was quite skilled in getting me to redirect my thoughts and bringing me back within the outer edges of my Green. We then discussed if there was any reason we could not continue. Since (a) we knew of no compelling reason why we couldn't continue the flight; (b) all systems were operating normally; (c) all flows; procedures; and checklists had been reaccomplished and were complete; (d) we were back in the Green; and (e) I knew the flight could operate safely; we decided to continue the flight. I made a short and embarrassing PA to the Passengers and apologized for the short wait while we dealt with a cockpit issue. We then flew an otherwise uneventful flight to ZZZ; blocked in six minutes early; and went into Crew rest.  The Crew threat of Expectation Bias was certainly present. I expected the start lever check to be usual; but it wasn't. Also I made a procedural (checklist) error as I did not accomplish the 'start levers' step correctly during the Before Takeoff Checklist. Several suggestions come to mind in order to prevent this from happening again. Primarily; I have changed the way that I check the start levers in the 'idle' detent. No longer will I hold them with my thumb and forefinger. And no longer will I nudge them rearward; but only forward and down. Additionally some verbiage in the operating manual might be helpful where none exists now. In the Before Takeoff Checklist section; perhaps include a note; warning; or caution about the consequences of inadvertent; unintended movement of the start levers out of the idle detent during that step of the checklist. Also; in the Before Takeoff Checklist; perhaps include some expanded text to describe the intent of what is desired here to accomplish this step; i.e.; whether or not to touch the start levers; andhow to touch the start levers if touching the start levers is intended for verification. Finally; a few simple design changes to the start levers and idle detent could prevent a recurrence. Lastly; and just as a general safety comment; looking back at the event; I am not happy that it occurred. But I am convinced that we employed our risk assessment processes well and that the model worked and I am happy about that. Since we can't eradicate all risk; I will continue to apply our risk assessment principles and processes to mitigate that risk that can't be eliminated.
Pilot of B737 unintentionally shut down both engines during start lever check on the Before Takeoff Checklist. The crew then methodically completed all takeoff preparations and procedures before completing the flight.