Date: 201401
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: IMC
Weather elements / visibility: Fog
Light: Night
Aircraft: B737-400
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: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Distraction
Second reporter function: Captain; Pilot Flying
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence; Inflight Event / Encounter Unstabilized Approach; Inflight Event / Encounter CFTT / CFIT
Detector: Automation Aircraft Terrain Warning; Person Flight Crew
When detected: In-flight
Result: Flight Crew Executed Go Around / Missed Approach; Flight Crew Became Reoriented; Flight Crew Took Evasive Action; Flight Crew FLC complied w / Automation / Advisory
Contributing factors: Human Factors; Weather; Environment - Non Weather Related
Primary problem: Ambiguous

Narrative: 1;200 RVR at our destination. Briefed CAT 3 to 16. Fog layer tops at around 500 FT. Clear above. We were vectored to about a 20 mile final and assigned 190 KTS for spacing. We configured and slowed to meet speed request at Flaps 1. After glideslope intercept ATC requested 160 KTS to final. As we attempted to slow there was a quartering tailwind. Aircraft wasn't slowing enough so we put the gear down. We slowed to 160 KTS early in the approach. We both thought to turn on the engine anti-ice but due to an inversion; it was 13 or 14C so we turned it back off. At this point we were configured for the initial approach and began the CAT 3 procedures. We made our pertinent calls to both ATC and for our approach. Between the final approach fix and the 500 FT call; I believe I fixated on the temperature for turning ON the engine anti-ice which probably happened at about 900-1;000 FT AGL. The airport surface temperature was 1C. After the 500 FT call; the Captain realized our speed was still 160 KTS and our flaps weren't properly configured. I can't recall if we were at Flaps 10 or 15. I believe F15 because we selected F25 right about when the TOO LOW TERRAIN GPWS sounded. We immediately executed a missed approach and I know I went from F25 to F15. After an uneventful missed approach and subsequent CAT 3 approach to 16R; we parked the jet at the gate and completed our checklists. We then conducted a thorough debrief full of embarrassment and disappointment.I feel ultimately that the responsibility was mine as the overall situation monitor to catch the flap position while the Captain performed a HUD monitored approach. We were slowed so early on in the approach that we put the gear down and conducted the landing checklist very early. I then fixated on the engine anti-ice which normally could be just turned on and forgotten but the temperature inversion precluded that. From Final Approach Fix in I concentrated on the autoland and HUD specific monitoring and the prolonged low speed lulled me into a feeling of being configured. Neither I nor the Captain considered this an acceptable performance.


Second narrative: Upon reflection; I became distracted by the need to turn on the engine heat during a critical phase of flight. The extended time on final above the fog layer; helped cause a funneling and tunneling effect. We configured early and started the landing check. We never completed it as we were both concerned about the engine anti-ice. I was also focused on spacing. Ultimately; it was my responsibility to ensure we complied with our procedures. Because I didn't ensure the highest priority of flying was met (Aviate); we found ourselves in an undesired state. We both learned a valuable lesson. On a positive note; we made the decision to go-around and that went well. We've fully debriefed each other.


Synopsis: A B737 crew became distracted during a long slow CAT 3 final accompanied by a temporary; warm temperature inversion on a very cold night so when the EGPWS alerted TOO LOW TERRAIN at 500 FT because only Flaps 25 was selected; they executed a go-around.