Date: 201404
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Night
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Final Approach
Airspace: Class C ZZZ
ATC / advisory: TRACON ZZZ
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Distraction
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Detector: Automation Aircraft Other Automation; Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented
Contributing factors: Procedure; Human Factors; Environment - Non Weather Related
Primary problem: Human Factors

Narrative: On approach; dogleg to final and descending in night VFR conditions to the visual approach; Approach Control called out potentially conflicting traffic in close proximity to the final approach course waypoint we were cleared to. The TCAS target appeared to be very slightly north of the final approach course and appeared to me on the ND scale selected to be about 1/2-1 mile from the waypoint. I remember being very concerned about how close the traffic was to my projected rollout point on final. We were handed off to Tower. Continued visual scan for the traffic was unsuccessful and as we rolled out on to the final approach; I believe GPWS stated 'GLIDESLOPE' and simultaneously the Captain stated I was below glidepath and I manually took control of the aircraft; added power; and quickly reestablished glidepath parameters within 5-10 seconds. Simultaneously; Tower called low altitude alert and Captain responded that we were correcting. Normal approach parameters were established well above 1;000 FT (I cannot remember the exact altitude but I remember it not being concerning to me in terms of terrain proximity) and approach was continued uneventfully to a full stop landing. I was obviously concerned with the proximity of traffic to my aircraft that I couldn't visually acquire and lost my vertical SA to some degree on a visual approach at night. What would be helpful here in diagnosing the error would be my recollection of the entire Mode Control Panel configuration. I believe that at the point of error; the altitude window was set for 500 FT or thereabouts for a visual approach (this is based on my recollection that the Captain reset the altitude window at time of error to an appropriate glidepath intercept altitude); VOR/LOC was selected; and if I were to guess; FL change was likely engaged; which would cause the aircraft to deviate below the glidepath. Again to emphasize; I cannot fully recollect the configuration as the event happened so fast and I immediately took control of the aircraft manually. I'm not sure what the solution is here other than emphasis on proper MCP configuration and more reliance on TCAS to keep me clear of traffic. I lost my situational awareness due to channelized attention on what I perceived as a threat that I wanted to trap; but in doing that; I failed to notice the ensuing developing threat to my altitude and failed to trap that one until safety systems warned me of the glidepath deviation. So for me; it becomes an issue of prioritization.....I mis prioritized the two threats occurring simultaneously. I should have been focused on flying the aircraft and then rely on the Captain's visual scan for traffic and TCAS to keep me clear of any conflict.




Synopsis: B737-800 First Officer reports descending below glideslope during a night visual approach due to fixation on traffic near the FAF. A glideslope annunciation by the aircraft and a low altitude alert from the Tower result in a manual climb to intercept a proper glide path.