Date: 202107
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class B ZZZ
Aircraft component: Trailing Edge Flap
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Human factors: Troubleshooting
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Weight And Balance
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Overcame Equipment Problem; Flight Crew Landed As Precaution; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Returned To Departure Airport; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: During initial climbout from Runway XXR; the Trailing Edge (TE) flaps failed to retract from the takeoff position; flaps 1. I noticed this; as I prepared to place the Landing Gear lever to OFF and autobrakes to OFF. I directed to the FO (First Officer); who was PF (Pilot Flying); to slow to 210 KIAS while I coordinated with ATC to level off at 6;000 ft. MSL and Hold PPOS; approximately 15 miles southeast of the airport. I pulled out the QRH as we assessed our indications. The TE Flap gauge showed a slight split in the needles; with the R needle slightly retracted from flaps 1 and the L needle at flaps 1. I considered both Flap Asymmetry and Flap Disagree Checklists; and we decided the Asymmetry Checklist was more correct; despite the flap lever being UP. The PF did indicate very slight anomalous roll indications; prior to engaging the AP (Autopilot). I then informed the Passengers of our issue; briefed the FAs (Flight Attendants) that we would hold and work the problem and that we would be diverting to either ZZZ1 or ZZZ. Dispatch was very helpful in getting the Company Operations Center involved and suggesting ZZZ; editing the Release and giving us fuel and weight and balance data for worst case scenario. We began the QRH; holding at the deferred items for descent and landing. I then coordinated for the RNAV Z XXR Approach; briefed the Passengers of our decision to return to ZZZ; and briefed the FAs on the ETA and after landing plans. We briefed and commenced the approach; completed the QRH; ran brake cooling and reviewed the plan one last time. The PF flew a very nice approach at Vref 40 + 30 to a smooth flaps 1 landing with AB3 required and selected. On rollout I suggested he quickly disarm the AB and let the aircraft roll out at max reverse thrust to allow for more brake cooling. The data indicated 18 minutes of cooling at the gate so we taxied to the gate; shut the aircraft down and coordinated with Operations and [Maintenance Control]. Training and Company operational priorities had us well-prepared and allowed us to handle the issue safely and with ease.




Synopsis: B737 Captain reported trailing edge flaps did not retract after takeoff and was diagnosed as a flap asymmetry problem; resulting in an air turn back.