Date: 201501
Local time of day: 1801-2400
Location: DEN.Airport, CO
Flight conditions: IMC
Weather elements / visibility: 10
Aircraft: B737-700
Operator: Air Carrier
Flight phase: Final Approach
Airspace: Class B DEN
ATC / advisory: Tower DEN
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Other / Unknown
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Conflict Airborne Conflict; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance
Detector: Automation Aircraft RA; Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Executed Go Around / Missed Approach; Flight Crew FLC complied w / Automation / Advisory
Contributing factors: Human Factors; Procedure; Company Policy
Primary problem: Ambiguous

Narrative: While stabilized with Localizer and glideslope capture on ILS to Runway 35L at DEN; with an aircraft on parallel approach to Runway 35R; we received a TCAS Resolution Advisory (RA) warning. As pilot flying I disconnected autopilot and autothrottle and complied with 'Adjust Vertical Speed' RA.  I was unable to regain a stabilized approach; so I called for a missed approach to include the verbiage 'Set Missed Approach Altitude.' Tower assigned an altitude to climb to which is the reason for this report. The pilot monitoring (PM) dialed (and he believes read back) 9;000 feet in the MCP. When climbing through approximately 8;000 feet MSL; the Controller notified us he assigned 7;000 feet. The PM insisted we had been cleared to 9;000 feet. We were then assigned a departure frequency and received vectors back to Runway 35L for a landing. When ATC declared we had climbed to the wrong altitude; I thought back and could not remember what clearance was given. I must have been task saturated with the missed approach and did not adequately focus on hearing the clearance. I am fairly confident I verified 9;000 feet in the MCP; but I was not aware this was possibly the wrong altitude. I recently watched the video about the low airspeed incident during a go-around and was in the 'Yellow to Red' trying to ensure I did the steps correctly which diverted attention from hearing the clearance consciously. Perhaps a preventive measure would be mentally 'chair-flying' the steps more often so it takes less mental capacity.


Second narrative: During the approach to Denver; we received a TCAS Resolution Advisory (RA). The Captain complied with the RA and stayed above glide path. As a result; we were unable to meet stable approach criteria by 1;000 feet. The Captain initiated the go-around. After the captain called 'Set Missed Approach Altitude'; I began running the altitude up as I called the missed approach. Tower told us to maintain runway heading and climb to 9;000 feet. I read back the clearance and reset the altitude in the MCP to 9;000 feet. As we reached 9;000 feet; Tower called us and said we had been told to maintain 7;000 feet. I actually believe we complied with our assigned clearance and the Controller made a mistake.


Synopsis: B737-700 flight crew receives a TCAS RA during a night IMC ILS caused by traffic on the parallel runway and complies with the RA command to reduce sink rate. This results in an unstabilized approach and a go-around. The missed approach altitude assigned by ATC is misunderstood by the First Officer resulting in an overshoot.