A B737 captain reported a flap asymmetry on final with the gear down; but during a go-around to comp...

Narrative:

On approach ILS zz approach; at 2000 feet flaps 5 selected and 180 KIAS; we commenced configuring the aircraft to land. At the FAF we intercepted localizer and glideslope and started down the glideslope while slowing and configuring the aircraft. I was slowing and configuring the aircraft when I sensed the aircrafts attitude was not as expected for my configuration. I looked at the flap position indicator and noticed a split flap situation with one flap at 1 and the other between up and 1. I initiated a go-around. The flap handle was at 30; and not knowing the current flap status; I left the flap handle at 30 and raised the landing gear. As soon as the landing gear retracted the flaps immediately and rapidly dropped to flaps 30 position; and the configuration warning horn sounded. At 2000 feet with the aircraft in a stable flight path; I lowered the landing gear. The configuration warning horn ceased and I had three down and locked landing gear with flaps at 30 and a green light. We [advised] ATC of our situation and received radar vectors back for a visual approach to runway. An uneventful approach and landing was conducted using normal checklists. Company maintenance was consulted at the gate and a logbook entry made. Company dispatch was also contacted and briefed.

Original NASA ASRS Text

Title: A B737 Captain reported a flap asymmetry on final with the gear down; but during a go-around to complete the checklist; the flaps lowered to 30 as selected when the landing gear retracted. The aircraft returned to land.

Narrative: On Approach ILS ZZ Approach; at 2000 feet flaps 5 selected and 180 KIAS; we commenced configuring the aircraft to land. At the FAF we intercepted LOC and glideslope and started down the glideslope while slowing and configuring the aircraft. I was slowing and configuring the aircraft when I sensed the aircrafts attitude was not as expected for my configuration. I looked at the flap position indicator and noticed a split flap situation with one flap at 1 and the other between up and 1. I initiated a go-around. The flap handle was at 30; and not knowing the current flap status; I left the flap handle at 30 and raised the landing gear. As soon as the landing gear retracted the flaps immediately and rapidly dropped to flaps 30 position; and the configuration warning horn sounded. At 2000 feet with the aircraft in a stable flight path; I lowered the landing gear. The configuration warning horn ceased and I had three down and locked landing gear with flaps at 30 and a green light. We [advised] ATC of our situation and received radar vectors back for a Visual Approach to Runway. An uneventful approach and landing was conducted using normal checklists. Company Maintenance was consulted at the gate and a logbook entry made. Company Dispatch was also contacted and briefed.

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.

Attributes
ACN	1238742
Time
Date	201502
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Component
Aircraft Component	Flap/Slat Control System
Person 1
Function	Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 165 Flight Crew Type 9000
Events
Anomaly	Aircraft Equipment Problem Less Severe

A B737 captain reported a flap asymmetry on final with the gear down; but during a go-around to complete the checklist; the flaps lowered to 30 as selected when the landing gear retracted. The aircraft returned to land.