B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 165; Flight Crew Type 9000
Situational Awareness; Human-Machine Interface; Confusion; Training / Qualification
Aircraft Equipment Problem Less Severe
Flight Crew FLC complied w / Automation / Advisory; Flight Crew Took Evasive Action; General Declared Emergency
Aircraft; Procedure
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.
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.