Date: 201701
Local time of day: 1801-2400
Location: DFW.Airport, TX
Flight conditions: IMC
Aircraft: Airbus Industrie Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class B DFW
ATC / advisory: Tower DFW
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Human-Machine Interface; Situational Awareness
Second reporter function: Pilot Flying; Captain
Anomaly: Deviation - Speed All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Unstabilized Approach; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Executed Go Around / Missed Approach
Contributing factors: Aircraft; Human Factors; Company Policy
Primary problem: Human Factors

Narrative: Approach to runway 35 center in Dallas; captain was flying. Weather was IMC; ATIS reporting 500 overcast; pilot report indicated ceiling on final 900 feet. On our first approach we were cleared to join the localizer at 2100 feet; then subsequently cleared for the ILS. Established on the localizer; when the glideslope came alive we continued to configure with gear down and flaps three. The captain called for the landing checklist and before the checklist was started we realized we had forgotten to arm the approach and had flown through the glideslope at 2100 feet. We declared a missed approach and continued to track the localizer at 2100 feet. It took about 15 minutes to get vectored around for another approach. At some point the ATIS was changed to 400 feet overcast but ceiling on final still reported at 900 feet. We also had received several reports of a significant wind shift occurring around 2000 feet which was complicating approaches. The wind was reported to shift from a tailwind of up to 30 knots to a headwind of 10 knots on the ground. We got vectored for our second approach and everything was proceeding normally until managed speed was set near the outer marker. At that point; the engines began to spool up for a few seconds before finally throttling back to adjust for the new target airspeed. We could not figure out what caused the engines to spool up momentarily (approach was activated and confirmed); but now our airspeed was much faster than it should have been. We were on glideslope at 1000 feet but still fast. Being distracted with our mistakes and confused by the jump in power and airspeed increase; I failed to make the required call out at 500. Landing was made well within the touchdown zone and we taxied to the gate.Both of us were tired and stressed after our mistakes on the first approach caused an unnecessary go around. We should have let that first approach go and treated the next approach as a fresh start.Although we could not figure out why the engines spooled up; it may have had something to do with the way we handled post-go around flight plan in the MCDU and set up for the next approach. Better familiarity with situations which may cause this would help to avoid recurrences.Just like with runway crossings; I should discontinue other duties so I can monitor in-flight transitions such as glide slope capture.


Second narrative: There is some confusion regarding our approach clearance. While on left base for 35C ATC issued a left turn to 030 to intercept the LOC and a descent to 2100'. Past experience dictated when in this location on an approach ATC instructions are almost unfailingly to turn to 030; maintain 2100 until established and cleared for the approach. That is the clearance I was expecting and that is the clearance I thought I got; so after turning to the intercept heading and starting my descent to 2100' I queried the F/O just as I was selecting the APP mode to verify with him that we were; indeed; cleared for the approach. He said that we were not. I then deselected the APP mode and engaged the LOC mode. I don't recall receiving an approach clearance after that point. Whether we were; in fact; given one off of the intercept heading (which is normal); or we received one after intercepting the LOC and I missed it; or we were never actually given an approach clearance; I am not actually certain. Regardless; my trigger to arm the APP mode was not repeated and I missed that task. All was routine during the vectors and set-up for approach #2. When we were once again on base leg; we were given the expected instructions to turn to the intercept heading and to maintain 2100' until established on the approach; cleared for the ILS 35C. All was routine. As the Glide slope came alive I started configuring the aircraft beyond flaps 1 which was the setting I was at for the intercept. When I got to the 'gear down; Flap 3' call I switched the speed from selected to managed speed. And that's where the situation quickly became distracting. When I managed the speed the airspeed bug changed colors and reappeared on the target speed of 147. However; simultaneously; the power; instead of reducing at this point; increased significantly. My first reaction was to turn off the autopilot; which I did; and then to disconnect the auto-thrust; which I did not do; because just as I was about to manually reduce the power it started coming back down. At this point I was on LOC and on glide slope where I remained; but slowing of the airplane to the proper speed did not occur until late into the approach; the sink rate was higher than normal because of the higher speeds and at one point momentarily exceeded limits as the glide slope approached a 1/4 dot deviation. Additionally; I selected flaps full below the acceptable altitude in an effort to slow the airplane down more quickly. Once I got caught up in the trap of fixing what had gone wrong; I missed several triggers to go-around. I became fixated on completing the approach.


Synopsis: Air carrier crew reported executing a missed approach after not arming approach mode causing the aircraft to fly through the localizer.