Date: 201405
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Weather elements / visibility: Windshear
Light: Daylight
Aircraft: A319
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class C ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Autoflight System
Component problem: Design
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Training / Qualification; Workload; Confusion; Distraction; Human-Machine Interface
Anomaly: Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Detector: Person Flight Crew
When detected: In-flight
Result: Aircraft Automation Overrode Flight Crew; Flight Crew Executed Go Around / Missed Approach; Flight Crew Took Evasive Action
Contributing factors: Aircraft; Human Factors; Procedure; Manuals
Primary problem: Ambiguous

Narrative: The flight to our filed destination was standard with the First Officer flying the leg. We had already flown several flights together both on this sequence and on previous sequences in the past. I consider the First Officer a highly skilled and competent pilot with a wide breadth of experience in both civil and military aviation. The routing to our destination was standard as per dispatch. The routing terminates at the airport; so it is expected that Approach Control will vector you to the approach starting at or above 10;000 MSL. As we descended approaching 10;000 MSL we were given vectors to the East side of the airport for a visual approach to Runway 19 on the west side of the airport. The aircraft was in selected Speed Mode and open descent thus allowing the crew to enter a visual pattern. Approach Control early on asked if we had the field in site.  Knowing that several months prior the news had continually reported a story of a freight aircraft landing at the wrong airport while attempting a visual approach into this airport; the First Officer and myself were focused on ensuring that we positively identified the nearby airport vs. our destination since we would be approaching from the east. This 'threat' as introduced by ATC asking for a visual ID of the airfield subsequently resulted in an 'error' on not activating the approach mode passing through 10;000 MSL as per A319 procedures. We entered downwind and immediately became concerned with the current wind conditions on the field.  Though within ops limits for the A319; we discussed that landing this aircraft in gusty conditions introduces some potential issues with the auto thrust system and the 'ground speed mini' system that is designed to maintain a constant ground speed during the approach.  At approximately 3;000 MSL; we turned to a left base with the field positively identified. The aircraft was in selected speed mode; the flaps were at 1 and the First Officer was hand flying the aircraft using flight director guidance; manual stick and autothrust. The FMGC was set up with the ILS approach and the 'green line?' extended off the FAF. The aircraft was being steered via heading select mode. At 3;000 MSL and turning left to final approach both pilot immediately noted the aircraft engines spooling up and the aircraft beginning to accelerate toward 200 KIAS. I immediately called 'watch your speed' and simultaneously looked at the speed select window. I noted the speed had reverted to 'managed' mode so I immediately pulled the speed select knob and spun the speed back to below 150 KIAS. As I spun the speed select knob I noted the airspeed indicator was just at or slightly below the barber pole but the aircraft and the airspeed trend arrow bouncing erratically due to the wind gust of up to 30 knots. Simultaneously First Officer pitched the aircraft up in an attempt to prevent over speeding the flaps. This minor altitude deviation resulted in the aircraft no longer being in a position to land; and thus we executed a right 270 to position the aircraft for a normal landing. The First Officer and [I] reviewed the incident during our layover and continued to use our available publications to ascertain as to why there was an inadvertent activation of the approach mode. Notes concerning this issue can be found in Operation Manual; though the Manual fails to explain why the approach mode will inadvertently activate. I have concluded that the A319 will automatically activate the approach mode when below 7;200 MSL (Ops Man Vol II); but if not established on a published segment of the approach; within a yet to be determined radial distance of the IAF. The issue is that since the aircraft is not on the approach segment but below 10;000 MSL; the aircraft attempts to accelerate to the default managed speed of 250 KIAS. This aspect must be explored in more depth by the appropriate Company department and subject matter experts to be verified. The anomaly cited above mustbe researched; validated and then taught as part of both initially qualification but also as part of recurrent training.




Synopsis: An A319 crew was surprised by the aircraft transitioning to Managed Speed and accelerating to overspeed the flaps while on approach at 3;000 FT in the HDG and SPD SEL modes; APP not activated; so the crew executed a go-around; but returned for a normal landing.