Date: 201602
Local time of day: 1801-2400
Location: IAD.Airport, DC
Flight conditions: IMC
Weather elements / visibility: Icing
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Initial Approach
Airspace: Class B IAD
ATC / advisory: Tower IAD
Aircraft component: Aerofoil Ice System
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Distraction
Second reporter function: Pilot Flying; Captain
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Other / Unknown; Inflight Event / Encounter Unstabilized Approach; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Contributing factors: Company Policy; Human Factors; Weather
Primary problem: Human Factors

Narrative: On approach into IAD Runway 19L the flaps were still in transit to the final flap setting of 40 degrees at 1;000 feet Above Field Elevation (AFL) and we elected to continue the approach. I was Pilot Monitoring (PM) and the Captain was Pilot Flying (PF). We had an over enthusiastic jumpseater who continually was offering us flying instructions. Enroute to IAD; ATIS was reporting freezing rain and light freezing rain with Mu readings of the low thirties to the mid-twenties for the landing Runway 19C; with reports of poor braking action. The weather at our original alternate deteriorated and the dispatcher changed our alternate. [The new alternate] was forecast for possible snow at arrival time.We briefed a flap 40 landing. During radar vectors to final; Approach Control informed us 19C was closed and 19L was open; requiring us to set up an approach for 19L; re-brief and re-check landing data for that runway. A preceding aircraft reported fair braking on Runway 19L. Prior to the glide path interception point; IAD Tower cleared us to land; but was now reporting a tailwind. Prior weather reports did not contain a tailwind. We checked the penalty for the tailwind; found we were within limits and selected max autobrakes. The last-minute tailwind report definitely rushed things.The landing was at the 1;000 foot markers and we stopped the aircraft. The Captain and I debriefed the event thoroughly and decided to file ASAP reports because we believe in the importance of stabilized approaches and wanted to be proactive. Reflecting on this I would call for a go-around if not completely configured for the approach. Additionally jumpseaters should be just that; an extra set of eyes; not flight instructors.


Second narrative: My decision to deviate from procedure was based on a couple of factors. First; the braking action report on 19L was significantly better than 19C. My concern was that a go-around and re-sequencing would put us back on the approach after the runway had only gotten worse from the light freezing rain. While we had sufficient fuel to make it to our alternates; both were forecasting snow for an arrival time. Great Lakes cities can experience sudden heavy snow with poor visibility and slippery conditions. Finally; the aircraft was on course and glide path; with a normal sink rate. The landing was at the 1;000 foot markers and we stopped the aircraft with plenty of runway remaining. My first officer and I debriefed the event thoroughly and decided to file reports because we believe in the importance of stabilized approaches and wanted to be proactive. I am fortunate that the flight was with an experienced FO.Finally; I'd like to say that I do not believe that pilots are at liberty to pick and choose what elements of a stabilized approach are required. It was a difficult decision and a lesson for me. Looking back; I would recommend a go-around if not completely stabilized for the approach. One last point; we had a jumpseat rider that was a distraction in the flight; however it is my responsibility to manage the situation.My recommendation is to not deviate from Company's stable approach requirements. It's a professional letdown for me to say I flew an unstable approach and it won't happen again.


Synopsis: B737-800 flight crew describe passing 1;000 feet AGL on final with the flaps still in transit to 40 degrees. They cite distractions from weather; last minute runway change and comments from a jumpseating First Officer.