Date: 201605
Local time of day: 0601-1200
Location: ZZZ.Tower, US
Flight conditions: VMC
Light: Daylight
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: Trailing Edge Flap
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Executed Go Around / Missed Approach
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: While being vectored for the approach we began our final configuration for landing. Approaching the outer marker in a shallow descent passing 2000 ft MSL I commanded for the flaps to be set at 30 degrees and we began the Before Landing Checklist. The F/O (First Officer); who was the PM (Pilot Monitoring); read flaps; and I responded 'flaps;' as I looked over at the flap gauge. We both verified on the flap gauge that the left flap was indicating 30 degree; while the right flap was still at the 25 degree indication. There was no indication of uncommanded roll; or yaw of the aircraft. 	We immediately decided to discontinue the approach and requested vectors or a holding pattern so we could run a checklist. We were cleared initially to 1500 ft MSL; and then up to 4000 ft. Climbing through approximately 1200 ft MSL; I reengaged the autopilot to get an additional level of automation working for me; so I could concentrate on the situation at hand. We pulled out the QRH; and ran the Trailing Edge Flap Asymmetry Checklist from the QRH. We completed the QRH Checklist and ran landing performance numbers for landing with flaps set at 15 degree. At this point the aircraft was taken care of; so it was time to notify the Company; the F/As (Flight Attendants) and the Passengers. The Pilot monitoring took care of these duties while I; as the PF (Pilot Flying); maintained radio communications with Air Traffic Control; and flew the aircraft. After all external notifications were done and checklists were complete; we requested vectors back to the approach course for landing. The approach and landing were uneventful; and we arrived with Maintenance waiting for us at the gate. I contacted Dispatch; and the Chief Pilot on Duty; by telephone; and spoke with Maintenance Personnel while my F/O briefed the Crew that was to take the aircraft. The aircraft was subsequently taken out of service for Maintenance; and my F/O and I proceeded to another gate and pressed on with our day.By using automation to lighten our workload; dividing up tasks and working together as a team to diagnose and address a mechanical situation; using the appropriate checklists; and letting other members of the Company Team know what was going on; an abnormal situation was handled in a methodical and professional manner by everyone involved.


Second narrative: During a visual approach; the PF (Pilot Flying) called 'Flaps 30; Before Landing Checklist.' We performed the checklist per normal procedure; and as the PM (Pilot Monitoring) was aurally stating 'FLAPS'; we both noticed that the Left flap was indicating 30; while the Right flap was indicating 25. Both indicators aligned with the index marks at each of the flap positions respectively.As the flaps were set to the final setting; neither of us noticed any rolling tendencies and the aircraft appeared quite stable. The PF took the safest course of action by electing to discontinue the approach; and requested the PM to notify the Tower. Tower was notified that we were going around; and we were instructed to fly runway heading. I cannot recall the altitude we climbed to initially (either 3000 ft or 4000 ft). During the normal go-around maneuver; flaps 15 was selected; and the flaps correctly retracted to the selected detent. We then were switched to Departure; where we were given box vectors within the terminal area; in order to complete the appropriate QRH Checklist (Trailing Edge Flap Asymmetry); and return for landing. VREF - 146 IAS & VTARGET-151 IAS based on an approximate landing weight of 113 pounds. After the QRH Checklist was completed; the PM notified the F/As as to the situation at hand; that we expected a normal approach and landing; and the amount of time to landing.Also; an announcement to the Passengers was made to notify them of the basic condition; and that we would be performing a checklist to allow us to return for landing. Ops was also notified. Finally; we advised Approach Control that we were ready to proceed inbound for landing. A flaps 15 approach and landing was conducted at a nominal touchdown rate of descent; with an approximate brakes speed of 140 IAS. The aircraft turned off and taxied to the gate where a normal deplaning occurred; and Maintenance was waiting.


Synopsis: B737 flight crew reported a split flap indication (25 and 30 degrees) with no rolling tendency and no flap asymmetry indication. A go-around was initiated and the flap lever was moved to 15 and the flaps both moved to 15. QRH procedures were accomplished and a flaps 15 landing ensued.