Date: 201502
Local time of day: 0601-1200
Location: D01.TRACON, CO
Flight conditions: VMC
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class B DEN
ATC / advisory: TRACON D01
Aircraft component: Turbine Engine
Component problem: Design
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Human-Machine Interface
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Less Severe; Conflict Airborne Conflict
Detector: Automation Aircraft RA; Automation Aircraft TA
Result: Flight Crew Took Evasive Action
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: We were on a visual approach just about to intercept the localizer. I was hand flying the airplane with auto-throttles OFF. Just as we were approaching CHOLA; I observed a pop up TCAS target at 1130 position 500 feet below us in the climb. I notified the First Officer of the target and he reported it to ATC. Simultaneously we got an aggressive RA to Climb; Climb NOW and ATC gave us a traffic alert climb immediately! I went to TOGA (Take Off/Go-Around) thrust from flight idle and began to follow the RA guidance on the VVI. To my and the first officer's surprise; the thrust took 4 to 5 seconds to go to TOGA!!! Recognizing the delay in thrust response; I started a right turn away from the TCAS target to evade the target laterally. The FO reported to ATC we were in a TCAS climb and called for me to keep climbing and confirmed I had TOGA selected. As thrust finally went to TOGA and with the turn away from the target; we began to aggressively climb and the RA conflict resolved. We simply could not believe how long it took for the thrust to go to TOGA! We wrote up the airplane thrust system upon arrival at the gate in DEN. The aircraft was taken out of service to test the thrust system. I called approach and they concurred what data that had at the time indicated we had 200 feet and 1 mile separation.


Second narrative: We were on a vector to intercept the ILS; and had just been cleared for the visual approach to that runway. The captain was hand flying the aircraft; with the autothrust off; the flaps were up; and we were leaving 10;000 feet and descending to 7;000 feet. As we approached CHOLA intersection we saw a TCAS target appear on the ND; at about the 1130 position and about 300 feet below and climbing. The captain remarked about the traffic and I called ATC and advised them of the traffic. We then received a climb command from TCAS. The captain began the TCAS climb; pushing the throttles to TOGA. ATC then directed us to make an immediate climb. I responded that we were executing a TCAS RA climb. With the throttles at TOGA from idle thrust; the power took about 4 to 5 seconds to respond. Because of the lag; the captain also began a turn away from the target. We never acquired the target visually; and it passed below us and continued away from us. We talked with the controller and proceeded to re-intercept the visual approach and landed uneventfully.


Synopsis: A320 flight crew reports receiving a TCAS RA while descending to 7;000 feet with the engines at flight idle. After selecting Takeoff/Go-Around (TOGA) mode to evade; a 4-5 second delay is experienced before TOGA thrust is achieved.