Commercial Fixed Wing
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Flight Crew Last 90 Days 68; Flight Crew Type 8000
Distraction; Situational Awareness
Deviation - Altitude Excursion From Assigned Altitude; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance
Human Factors
We were at 4;000 feet MSL and approximately 25 NM from the airport on a direct course to SLGRR when we were cleared for a visual approach to Runway 17L at SDF. The First Officer set the crossing altitude of 2;500 feet in the MCP window and started a descent. I was looking for a GA aircraft that was on a converging course to the same runway as ours. As we were leveling off; we received a low altitude call from ATC. We visually identified the towers ahead of our position and the First Officer initiated a climb to 3;000 feet to increase our separation to the towers. Once the towers were behind us; he resumed the descent to SLGRR and completed the approach without further issues.I should have kept a closer watch on the flight path during this approach. A further study of the approach chart shows the towers we saw were quite a bit higher than any others around them; but not the highest obstacle on the chart.  This was easily missed in our chart review.
Flight was on the FRIZN 5 RNAV Arrival into SDF. Arrival and approach were briefed expecting THUND transition to a visual approach with ILS 17L as backup. Approach Control cleared aircraft directly to SLGRR waypoint; which is the FAF for the ILS.  Aircraft had been cleared down to 3;000 feet MSL.Crew mentioned to Approach Control that the airport was in sight and were cleared for a visual approach. 2;500 feet MSL was set into the altitude window to continue descent to FAF altitude. Crew then switched over to Tower and received landing clearance. Unbeknownst to crew; the flight path put the aircraft in the immediate vicinity of multiple radio towers ranging from 1;945 to 1;960 feet; which left only 500 feet of vertical clearance. At approximately the same time Pilot Monitoring saw the towers and mentioned them to Pilot Flying; crew received a call from Tower Controller stating that a low altitude alert was going off. Pilot Flying commenced climb to 3;000 feet to ensure 1;000 feet clearance margin. Remainder of approach was completed without incident.
Air carrier flight crew reported receiving a Low Altitude Alert from ATC due to towers close to the flight path of the aircraft.