Date: 201602
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Aircraft: Medium Large Transport
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ground ZZZ
Aircraft component: Ignition System
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Confusion
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew Became Reoriented
Contributing factors: MEL; Human Factors
Primary problem: Human Factors

Narrative: Our aircraft had APU MEL requiring an air start to get an engine running; however the APU could still provide electrical power. About the time we were finishing loading passengers we became aware of an Estimated Departure Clearance Time (EDCT) for our departure that was an hour and ten minutes away. I decided to complete the boarding process and made preparations for departure and pushed off the gate in order to free the gate up for the next arrival. On taxi out Ground gave us a clearance to taxi to the intersection of two taxiways to hold for the remainder of the time till the EDCT. Ground told us we could shut down engines; but be ready to move [20 Minutes before EDCT]. We acknowledged. While continuing taxiing I contemplated whether to leave the engine running since I only had about thirty minutes remaining and I would still be above minimum takeoff fuel or shut it down to save the fuel for airborne contingencies. I choose the later. When we stopped; I set the parking brake; looked at the fuel and time; told the First Officer my plan; checked the electrical AC synoptic page to ensure the APU was still a viable source of power and proceeded to shut the engine down. As I brought the thrust lever into the shut off detent; the FO said 'Wait' and it hit me as to what I had just done; shut down the engine which now required an air start cart to get it running again. We immediately formulated how we were going to resolve this dilemma. I contacted Operations and explained what I had done and what I needed. The FO explained to Ground what had happened and what we were working on with our Operations folks. Ground control said they would contact the City to provide escort to get what ever equipment was needed out to us. Operations had me call Maintenance and explain what we needed; which I did. All in all it took about 12 minutes for the air cart to arrive. We got an engine started and were ready to taxi to make our original EDCT. Other than one airplane that was asked to give way to the convoy of City escort vehicles; no operations on the airport were held up or adversely affected.The event occurred because I wasn't paying attention to my immediate situation. I let call from Ground about shutting down distract me and set a plan in motion that would have been 'normal' procedure on any other day. Before taking actions that take primary components off-line; verify the reason(s) with the other pilot. That little bit of extra time and thought could have produced the 'wait' call before it was too late.




Synopsis: With 30 minutes to go before assigned departure time; the captain of a commercial aircraft with an MEL that precluded the APU from starting engines; shut down the engine while stopped on a taxiway; forgetting that an air-start cart would be required to restart the engine. The crew requested and received an air-start cart to their location. Ground Control coordinated providing an escort.