B737 flight crew reported a flap extension error on approach leading to a go around.

Attributes
ACN	1604924
Time
Date	201812
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Flight Plan	IFR
Component
Aircraft Component	Flap Control (Trailing & Leading Edge)
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 156.85 Flight Crew Total 4543.05 Flight Crew Type 4543.05
Person 2
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument
Experience	Flight Crew Last 90 Days 135.35 Flight Crew Total 1870.18 Flight Crew Type 1056.52
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy Inflight Event / Encounter Unstabilized Approach

Narrative:

Descending into ZZZ and planning a normal flaps landing; speeds 147/142. I was the flying pilot and we were asked to slow from 230 to 170. I called for flaps 5 from 1 and then flaps 10. Speed was too great for flaps 10 so changed it to flaps 5. Right after that; intercepted the glideslope and called for gear down; flaps 15; and then flaps 30 and the landing check. As he was doing the landing checklist; first officer pointed out that we had a green light; but flaps were indicating 5. I verified this and though the airplane was handling like it was in final landing configuration; I checked the overhead and it showed leading edge devices were in the intermediate position. Not being able to verify which was true; called for a go around at 1;200 feet AGL and told tower. Normal go around was accomplished and flaps retracted normally. As we flew the heading and altitude; discussed what we would do if flaps didn't come down. We discussed getting flaps to 10 early to make sure it wasn't a system issue; and everything worked and we accomplished a normal landing. QRH was looked at on the ground; trailing edge flaps disagree was followed with the go around; and with what was going on felt best option was to go around and start again.

Original NASA ASRS Text

Title: B737 flight crew reported a flap extension error on approach leading to a go around.

Narrative: Descending into ZZZ and planning a normal Flaps landing; speeds 147/142. I was the Flying Pilot and we were asked to slow from 230 to 170. I called for flaps 5 from 1 and then flaps 10. Speed was too great for flaps 10 so changed it to flaps 5. Right after that; intercepted the glideslope and called for gear down; flaps 15; and then flaps 30 and the landing check. As he was doing the Landing Checklist; First Officer pointed out that we had a green light; but flaps were indicating 5. I verified this and though the airplane was handling like it was in final landing configuration; I checked the overhead and it showed leading edge devices were in the intermediate position. Not being able to verify which was true; called for a go around at 1;200 feet AGL and told Tower. Normal go around was accomplished and flaps retracted normally. As we flew the heading and altitude; discussed what we would do if flaps didn't come down. We discussed getting flaps to 10 early to make sure it wasn't a system issue; and everything worked and we accomplished a normal landing. QRH was looked at on the ground; trailing edge flaps disagree was followed with the go around; and with what was going on felt best option was to go around and start again.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.