Date: 202001
Local time of day: 1801-2400
Location: DEN.Airport, CO
Light: Night
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
Airspace: Class B DEN
ATC / advisory: Ramp DEN
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Human factors: Distraction; Communication Breakdown; Situational Awareness; Workload; Time Pressure; Troubleshooting
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew Became Reoriented
Contributing factors: Company Policy; Human Factors; Procedure; Manuals
Primary problem: Human Factors

Narrative: It was the third leg out of four on the last day of a four-day trip. The First Officer and I had worked well together throughout. Preflight was normal. We pushed on-time for our flight. During the push we noticed that our takeoff speeds had deleted off the CDU and there was a message stating 'OAT Disagree.' We set the brake; cleared off the Push Crew; and the First Officer told Ramp we'd be delayed a couple minutes. Ramp said to call back when ready to taxi. Both engines were running at this point. Since that speed's deleted situation rarely happens; we discussed it briefly. The First Officer then updated the Takeoff Data and resubmitted it via ACARS. Within seconds we received updated Takeoff Data which we reentered into the FMC. We then reaccomplished the Before Push checklist. The First Officer told ramp we were ready to taxi and they told us to taxi which we did. Both of us had forgotten the Before Taxi Flows and Checklist due to the distraction. While taxiing out; I did a throttle burst which caused the configuration horn and light to activate. It was then we realized we'd forgotten our Before Taxi Flows; Checklist and flaps. We set the flaps to 1 and continued taxi. Prior to takeoff with the aircraft stopped; we completed our Before Taxi Flows and Checklist followed by the Before Takeoff Checklist along with several more throttle bursts. Takeoff and the rest of the flight was uneventful.This was the first time in XX years here I've taxied without flaps. I'm disappointed in myself for allowing it. It was a textbook distraction error straight out of the simulator. There was plenty I could've done better to manage and prevent the situation. First and foremost; I needed to recognize the distraction for what it was and insured we completed our Before Taxi Flows and checklist and then dealt with the takeoff data issue. Then I should've used the Departure Plan Checklist after taxi instead of re-accomplishing the Before Push Checklist after the new data was entered. Lastly; when the configuration horn and light sounded we never referred to the Non-Normal [checklist]. Fortunately I'm in the habit of doing throttle bursts before they're required when notifying the Flight Attendants of takeoff. So the error was caught well before we reached the runway. But it never should have happened in the first place. And clearly our communication as a Crew was lacking since neither of us caught the situation prior to taxi.




Synopsis: B737 Captain reported a distraction during pushback caused them to taxi without flaps; and not complete the before taxi checklist.