Date: 201512
Local time of day: 0001-0600
Location: SDF.Airport, KY
Flight conditions: VMC
Weather elements / visibility: 5
Light: Night
Aircraft: A300
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Initial Approach
Airspace: Class C SDF
ATC / advisory: TRACON SDF
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Confusion
Second reporter function: Pilot Not Flying; First Officer
Anomaly: ATC Issue All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Airspace Structure; Procedure; Human Factors
Primary problem: Procedure

Narrative: Arriving on the RNAV Star; we were cleared direct [fix] to cross at 8000 feet. Prior to [fix] we were given descend to 6000 feet then later 3000 feet. We were instructed to join the localizer. At that point I selected heading mode and V/L on the MCP. Our heading was direct to a fix which is an extension of the Runway 35L localizer with no significant wind that would affect our course. At some point the controller; apparently in training; said: turn left to 020 to join the localizer do you have the runway in sight? The pilot monitoring repeated the heading and declared the runway in sight. The controller said: cleared for the visual. In the turn the localizer came alive and we joined and I selected LAND on the MCP. Immediately a voice came on and asked us why we departed from the arrival. The pilot monitoring said: we were cleared to join the localizer. The pilot monitoring asked: If you have a minute can you explain the problem. The same male voice in a very condescending manner repeated his previous statement insinuating that we had done something wrong. We continued the approach to land. After shut down the First officer and I discussed the event and were still puzzled. We did not over shoot the localizer or deviate from course. We decided the best thing to do would be to call the controller by phone which we did. The controller's supervisor said that they had discussed the event already. He said that our heading would take us toward the traffic for the parallel runway and that was the reason for the last minute heading change. Well of course it does; that's what happens when you come from the West. We both agreed that the instructions given to us on the approach should have been more precise. The trainee should have said: continue on the arrival to join; or present heading to join the localizer; which is what we did. Either way there should have been very little difference. The supervisor also said that there was no incident because of that issue.


Second narrative: [Report narrative contained no additional information.]


Synopsis: An aircraft on an RNAV arrival with a transition to the ILS approach was vectored off the arrival to join the localizer then cleared for a visual approach. There was confusion between the pilots and ATC if the crew was navigating in accordance with their clearance.