Date: 201508
Local time of day: 1801-2400
Location: SDF.Airport, KY
Flight conditions: VMC
Light: Night
Aircraft: Medium Transport; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class C SDF
ATC / advisory: TRACON SDF
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Human factors: Confusion; Situational Awareness; Workload
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT; Inflight Event / Encounter Unstabilized Approach
Detector: Person Air Traffic Control
When detected: In-flight
Result: Flight Crew Became Reoriented; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action
Contributing factors: Airport; Environment - Non Weather Related; Procedure
Primary problem: Procedure

Narrative: The only way to prevent this from happening in the future would be to not accept a tight base turn (with in 5 NM of the airport) the combination of the base turn and the shallow intercept vector how flexible I could be. If I had a steeper intercept I may have overshot the localizer course and caused a traffic conflict. Had I remained high to intercept the locilizer before descending I would not have in position to land (Landing would have required an excessive descent rate).The reality is this was a lose; lose; lose situation both the situations I described and the choice I made all should have resulted in a go around. The go around should have been instinctive with no hesitation but seeing the runway and being what I felt was well in position to land clouded my judgment.I was Flying to SDF at night time and we were vectored over the airport for 35R (there was inbound traffic on 35L). After we flew over the airport we were given a 160 heading for about 3 miles. Shortly there after ATC asked if we could accept a base turn in two miles for a Visual Approach. I accepted the base to visual clearance and continued the approach in accordance with the SOP procedure for a visual approach. we were issued a 270 heading then a 320 heading and cleared for the approach. I armed the approach and initiated the descent as we were already 1 1/2 dots high on the glideslope remaining on the 320 heading. Around 1;500 feet to 1;700 feet we received a low altitude alert from the tower. Still high on the glideslope by approximately 1 dot I arrested the descent asked my copilot to check the frequencies for the ILS and he also check the chart for obstacles. I had terrain up on my MFD. Seeing the airport outside and no Immediate risk from obstacles according to the approach chart; or visually by looking outside. I continued the visual approach to a landing with out incident on the 320 heading we did not intercept the Localizer until 900 feet AGL.    A low altitude alert is a serious situation and should not be taken lightly. There is always a degree of disbelief but If you were aware for the danger the Tower would not need to tell you. Not accepting turns inside the the FAF and being established on Altitude and course prior to the FAF would prevent this situation.




Synopsis: A Pilot on a night visual to SDF was issued a low altitude alert by Tower after descending rapidly from a high turning; descending base but intercepted the final at 900 feet AGL.