Date: 202106
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Aircraft: B737 MAX 8
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ground ZZZ
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Time Pressure; Situational Awareness
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: Taxi
Result: Flight Crew Became Reoriented; Flight Crew Overcame Equipment Problem
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: It was a hot day and the Flight Attendants (F/A's) were continually reminding us that the cabin was warm. We were also running about 30mins behind schedule so we felt rushed to make up time; and at the same time; cool the cabin as quickly as possible. Upon receiving our takeoff data at the gate we noticed we were going to have to do a bleeds off takeoff. It's been a while since either of us had done one so we took the time to look in the manual and review the procedure so we would properly execute the procedure. The aircraft was already warm and having MAX's long engine start sequence didn't help. After pushing back; with our departure runway practically right in front of us; being in a hot aircraft and 30 minutes late; we definitely felt the pressure to get things moving. After waving off the crew; our MAX engines finally got started. After the start during the First Officer's (F/O's) flow; he stopped at the air conditioning panel and realized we discussed the procedure for takeoff but not re-configuring after takeoff; nor had we discussed configuration taxiing to the runway. So while we waited for the MAX's engine warmup we discussed reconfiguration after takeoff as well as deciding to keep the air panel configured for takeoff; since it would be a very short taxi. After our discussion the F/O called for taxi. I released the brakes and since [the runway] was so close; I decided to do my pre-take off flow coming out of the ramp. So I chimed the F/A's and did a throttle burst all at once right out of the ramp area. And the mistake was made. We got the Takeoff Configuration Warning and horn. I stopped the aircraft; advised ATC we stopped; set the brakes and we accomplished the QRH items and with a successful throttle burst; did the Before Taxi Checklist and made an info only in the logbook. We then called for taxi and departed for an uneventful flight.Flows need to be accomplished and completed before any briefing discussions or questions take place. We both feel if we had waited to have the discussion after the FULL before taxi flow; we would have caught our mistake.


Second narrative: After the Before Push Checklist; Captain stated it would be an Engine Bleeds Off takeoff. (First Officer was in the Yellow.) I replied it has been two years since I preformed this takeoff procedure. To mitigate this risk; I read the Engine Bleed off Takeoff procedure in the MAX AOM [Aircraft Operations Manual] to Captain to be familiarized with the procedure. We pushed back [and] started the engines. During the engine starts; the Captain stated for me to call Ground after a minute and thirty seconds passed; after engine start; because we were so close to the runway. I performed my after engine start flow when I got to the bleeds; I stopped and I asked the Captain how he would like to configure them. Once configured we agreed enough time had passed to call for taxi. As we taxied; the Captain performed the before takeoff flow. We heard the Takeoff Configuration Warning. We stopped the aircraft and performed the proper checklists to reconfigure the aircraft for takeoff. Additive conditions involved in this event: First Officer (F/O) unfamiliar with Engine Bleeds Off takeoff. Very hot cabin. Short taxi to runway. Flight Attendant (F/A) PA about the hot cabin. Once I heard the announcement. I told the Captain I had not made announcement to the passengers about the hot cabin and if he wanted me to keep the right engine bleed on before takeoff as stated in the AOM.On my next Engine Bleed Off takeoff; I will complete my normal flow so the Captain will hear 'Standby Flaps'; then go back to re-configuring the bleeds properly. [I will] become more familiar with this procedure prior to my trips in the summer months.


Synopsis: B737 MAX 8 flight crew reported receiving a Takeoff Configuration Warning when the Captain performed a throttle burst check before the flaps were set for takeoff.