Date: 201208
Local time of day: 0601-1200
Location: MIA.Airport, FL
Flight conditions: Marginal
Weather elements / visibility: Rain; Thunderstorm
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Initial Approach
Airspace: Class B MIA
ATC / advisory: Tower MIA
Aircraft component: Flap Control (Trailing & Leading Edge)
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Workload
Second reporter function: Pilot Not Flying; Captain
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Unstabilized Approach; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew Became Reoriented
Contributing factors: Human Factors; Procedure; Weather
Primary problem: Human Factors

Narrative: Coming into approach on Runway 09 at Miami we had briefed a flaps 15 landing as a result of high gusting cross winds related to a hurricane. Approach was very gusty and included heavy precipitation at times. About the time of calling for gear down Tower reported a Regional Jet three miles ahead as we went IFR in heavy showers. Pilot flying called for S turns and began maneuvering for spacing while trying to acquire the Regional Jet visually. Rejoining final approach course at approximately 700 FT and made an uneventful landing. On taxi cleanup while First Officer brought flap handle up he noticed flap setting read 10 degrees and suspects that landing was made at 10 degrees setting. Both pilot flying and pilot not flying were so focused on attaining separation on the other aircraft and maintaining course; glide path and proper airspeed that we missed the 1;000 FT call. The approach was challenging with the weather; winds and ATC calls all happening at the same time. Possible solution may be to move the 1;000 FT 'Landing checklist complete' call to 1;500 FT.


Second narrative: Our flight involved extensive holding; a diversion; additional holding en route; and eventual approach to MIA in very windy (crosswind) conditions. The winds were nearly 90 degrees to runway heading and approximately 20 KTS. Light rain was reported; and approach path was turbulent. We acquired the runway several miles out; visual conditions but in rain which required high speed wipers. On final at approximately 1;500 AGL Tower cleared us to land and requested that we slow to final approach speed for Regional Jet traffic ahead. We could not slow any further because we were already at flaps 15 approach speed. I considered changing to a flaps 30 configuration but; ironically; I thought we might not get fully configured by 1;000 AGL and we would either have to go-around or get a FOQA phone call; so I opted to keep flaps 15. First Officer executed an S turn to the south to gain separation from the Regional Jet ahead. Rain increased in intensity as we approached runway; we were very preoccupied with the traffic separation; the huge crab due to the crosswind; the decreasing visibility due to rain; and the turbulence; all of which contributed to our not catching the fact that flaps were not at 15 but at 10. Landing was normal; with a slight bounce and normal rollout. First Officer executed a good approach and landing in very difficult conditions.I cannot stress enough just how aware I am of the seriousness of our error; in spite of the normal outcome. I need to put increased emphasis on monitoring the checklist; even when conditions outside the airplane may be more difficult than normal and requiring more of our attention. Checklist must prevail. Secondly; when conditions are challenging and there is no operational requirement for flaps 15; I will remain with flaps 30/40 which will provide me with a landing flap configuration warning if flaps are not set properly. At flaps 15; we use the 'flap inhibit' switch which disables any warning. While on downwind First Officer called for flaps 2; which is not normally used; I don't remember but if he then called for flaps 10; I might have then gone to flaps 5 (next slot) and so when he called for flaps 15; I might have gone to flaps 10 (next slot). I don't know if this is what happened; but it if did it certainly contributed to the final outcome; of course we should have visually verified the flap position on the gauge and the handle.


Synopsis: B737-800 flight crew reports planning a flaps 15 landing due to strong gusty crosswinds then becoming distracted during the approach and landing with flaps set to 10 degrees.