B737-800
Flight Crew Air Transport Pilot (ATP)
Distraction; Communication Breakdown; Situational Awareness
Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented
Human Factors
We were cleared for a visual approach Runway 34. Weather clear. The FO (First Officer) was flying with the aircraft on autopilot B. He set the altitude alert for 1;700 feet and began descending to that altitude from 2;000 feet. We were not aligned with the runway. He also selected full approach mode. The aircraft caught the glide slope and began to descend. Again; we were not lined up with the runway yet. At some point; the glide slope fluctuated; which made the autopilot kick off. Simultaneously; ATC called a low altitude warning for us. This was at approximately 1;300 feet. FO Corrected and began to climb back up to 1;700 feet and re caught the glideslope. We landed without further incident.The 'gotcha' point was selecting the full approach mode instead of selecting LOC first and letting the airplane capture that then selecting the full approach when the glide slope was lined up. I should have monitored the situation better. It was clear with perfect weather and the airport was clearly in sight. I was looking outside instead of inside. Maintain a cross check inside and outside.
While being vectored for an approach in RIC we reported airport in sight. We were then given the Visual. The crossing altitude at the FAF was set into the altitude window and the approach mode was selected; the autopilot was still on. The AP captured the glide slope and started a descent before capturing the localizer. When the autopilot lost the glide slope the AP kicked off at 1;300 feet. The Tower gave us a low altitude advisory and we climb back to 1;700 feet and flew an uneventful approach to Runway 34.In the future I will press the VOR/LOC mode to first intercept the LOC then press the Approach mode once establish on the LOC to capture the Glide Slope.
B737-800 flight crew reported descending too low on approach to RIC airport.