Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Workload; Time Pressure; Distraction; Situational Awareness
Aircraft Equipment Problem Less Severe
Air Traffic Control Provided Assistance; Flight Crew Overcame Equipment Problem; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Executed Go Around / Missed Approach; Flight Crew Diverted; Flight Crew Requested ATC Assistance / Clarification
Aircraft
During a fairly typical tight visual approach to ZZZ; we noticed that flaps were indicating 25 instead of the selected 40 during the landing checklist at about 1;300 feet AGL. We initiated a go-around; which was mostly normal other than flaps staying at 25 even when put to 15. We had an exceptional jump seater who was previously in the training department who was an invaluable member of the crew.As we handled the aviating and communicating; he handed me a QRH turned to the Trailing Edge Flaps Disagree checklist; which we confirmed and began; I handed aircraft control to my First Officer along with the radios. We had about 7.5 on the fuel; so we decided quickly that we were going to our alternate of ZZZ1. I ran the checklist and programmed up runway and communicated with dispatch through ACARS notifying them of our decision and need for landing data.We [identified as priority handling] out of an abundance of caution. The rest of the crew and finally the passengers were notified of our new destination; which we reached shortly thereafter. The first officer did an exceptional job of staying between flaps 25 over speed and the gear warning horn and also landed the plane. Maintenance worked on the plane for some time before hauling it away to a remote pad to continue troubleshooting the issue; which had happened previously.Always having an alternate is helpful as a baseline of required fuel is available when an issue like this arises. Our bingo fuel was for a clean configuration and we were flaps 25 but it was valuable information.
[Report narrative contained no additional information.]
Flight crew and jump seating instructor reported a 'Trailing Edge Flap Disagree' on approach resulting in a go-around and diversion.