Date: 201206
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: B757-200
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ground ZZZ
Aircraft component: Powerplant Fuel Valve
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Pilot Flying; First Officer
Human factors: Communication Breakdown; Confusion; Training / Qualification
Second reporter function: Captain
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew Became Reoriented
Contributing factors: Company Policy; Human Factors
Primary problem: Ambiguous

Narrative: During ground taxi to parking gate; unintentional shutdown of both engines. During taxi to gate after landing; the Captain advised me; the First Officer; he was shutting down one engine (for single engine taxi to the gate). I understood that the Captain wanted me to shut down an engine for single engine taxi to the parking gate and I started to move the right engine fuel control switch to CUTOFF. The Captain had shut down the left engine. As I took the right engine fuel control switch out of RUN; I saw that the left engine fuel control switch was in CUTOFF. I immediately returned the right engine fuel control switch to RUN but it was too late and the engine did not restart. I placed the right engine switch to CUTOFF. Both engines were now shut down and the Captain braked the aircraft to a smooth stop. The Captain had initiated the APU start before this sequence of events and it soon came on line to provide electrical power and pneumatic pressure. I restarted the left engine and we taxied to parking. Ground Control asked if we needed assistance and I explained that we did not and that we would be moving as soon as we reestablished power. The normal cabin lights went off with the loss of engine generator power and I made a Captain directed PA for the passengers to remain seated. Normal cabin lighting returned with APU generator power. Some passengers noticed white smoke from the right engine typical of the unspent fuel from my unsuccessful restart attempt. Some of this fuel vapor did make its way into the air conditioning ducts and cabin where flight attendants and passengers reported smelling it. We briefed the departing crew First Officer and Station Operations on this incident and passenger reactions. I believe a contributing cause in this incident is the recent changes to our our Carrier's normal engine shutdown SOPs where Captains now shut down engines or direct First Officers to perform this action vs the habit pattern of years where First Officers normally performed this task.


Second narrative: On taxi in we had a problem with the procedural change on engine shutdown from First Officer always doing it to Captain doing it unless delegated to the First Officer. As we were taxiing in; I announced that I was shutting down the left engine for the company encouraged single engine taxi. The First Officer reached for and started to shut down the remaining engine. He caught himself just as he moved the start lever to off and quickly returned it to run. The engine did not catch and the APU had not finished starting leaving us without power. We started an engine and taxied to the gate. Miscommunication combined with a tidal-wave of procedural changes and the emphasis on single engine taxi left us without power for a short period of time on the taxiway.


Synopsis: Following a procedural change; which in the past had the First Officer turn a B757 start switch OFF for single engine taxi; a Captain announced he was shutting down number one engine and the First Officer shut number two down out of habit.