Narrative:

At 2400 feet on a southeasterly heading ~7 NM north of sbn; southbend approach asked if we had the field in sight; and we did; and they cleared us for a visual approach to runway 27L. I asked the pilot monitoring (pm) for direct to misha; my intent was to LNAV/VNAV the approach to a manual landing once established on short final. The pm had initially extended the course off misha; and I asked for a direct so as to get good VNAV information. We turned to misha and I engaged LNAV. I reset the altitude window to 2000 feet which was the minimum altitude at misha. I realized that we were close to the FAF; so I directed configuring the aircraft with flaps/slats/gear. During this time; I dialed the altitude window to 800 feet thinking we were cleared and protected for a visual approach backed up by VNAV. The pm was busy configuring the aircraft and I realized we had not talked to tower. So I asked the pm if we had contacted tower. Southbend tower cleared us to land runway 27L. The pm told me that misha was not the FAF and that it was inside the FAF and 3 miles from runway 27L. The pm then stated we appeared low and asked where the runway was. I pointed out the first officer's (first officer) side window and said it's right there. Pm couldn't find the runway. As we slowed on speed to final configuration; I came inside one more time and noticed I was on the flight director and everything appeared normal. Pm again said we are low; where's the runway. That's when I looked at the nav display and realized that we were 1 mile north of misha and that our altitude was descending through 1300 feet. I started a climb. Simultaneously we received a low altitude alert call from tower. While in the climb I recognized the actual runway 27L was in the first officer forward window and that I had been lined up on either 27R or another runway or ground lights. We then incepted final and landed.in short; I wasn't looking at the actual runway and the pm had become distracted with an ACARS message and forgetting to switch to tower. I believe the aircraft was in flight level change instead of VNAV. I followed the flight directors as the aircraft slowed to the speed set in the speed window. I did not notice the aircraft descended below 2000 ft; the altitude set in the FMS at misha. When the pm asked where the runway was; I bit off on something that wasn't the runway. When the pm told me misha wasn't a normal FAF; I expected us to be low. So when he first alerted me to being low; I thought this was normal since we were closer to the runway. When the pm questioned our altitude a second time; that's when I realized misha was off the nose and we had departed 2000 ft.FMS mode awareness. I failed to ensure we were in VNAV and I blindly followed the flight directors. I also should have immediately scrutinized our altitude when the pm first alerted that we were low. I also will not accept a visual approach inside the FAF unless we are certain where we are and that our altitude is appropriate.

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Original NASA ASRS Text

Title: Air carrier flight crew reported during a night visual approach to SBN descending below the FAF altitude for Runway 27L. Flight crew climbed; intercepted final and landed.

Narrative: At 2400 feet on a Southeasterly heading ~7 NM north of SBN; Southbend Approach asked if we had the field in sight; and we did; and they cleared us for a Visual Approach to Runway 27L. I asked the Pilot Monitoring (PM) for direct to MISHA; my intent was to LNAV/VNAV the approach to a manual landing once established on short final. The PM had initially extended the course off MISHA; and I asked for a direct so as to get good VNAV information. We turned to MISHA and I engaged LNAV. I reset the Altitude window to 2000 feet which was the minimum altitude at MISHA. I realized that we were close to the FAF; so I directed configuring the aircraft with flaps/slats/gear. During this time; I dialed the altitude window to 800 feet thinking we were cleared and protected for a visual approach backed up by VNAV. The PM was busy configuring the aircraft and I realized we had not talked to tower. So I asked the PM if we had contacted tower. Southbend Tower cleared us to land Runway 27L. The PM told me that MISHA was not the FAF and that it was inside the FAF and 3 miles from Runway 27L. The PM then stated we appeared low and asked where the runway was. I pointed out the First Officer's (FO) side window and said it's right there. PM couldn't find the runway. As we slowed on speed to final configuration; I came inside one more time and noticed I was on the flight director and everything appeared normal. PM again said we are low; where's the runway. That's when I looked at the Nav Display and realized that we were 1 mile north of MISHA and that our altitude was descending through 1300 feet. I started a climb. Simultaneously we received a low altitude alert call from tower. While in the climb I recognized the actual runway 27L was in the FO forward window and that I had been lined up on either 27R or another runway or ground lights. We then incepted final and landed.In short; I wasn't looking at the actual runway and the PM had become distracted with an ACARS message and forgetting to switch to tower. I believe the aircraft was in Flight Level Change instead of VNAV. I followed the flight directors as the aircraft slowed to the speed set in the speed window. I did not notice the aircraft descended below 2000 ft; the altitude set in the FMS at MISHA. When the PM asked where the runway was; I bit off on something that wasn't the runway. When the PM told me MISHA wasn't a normal FAF; I expected us to be low. So when he first alerted me to being low; I thought this was normal since we were closer to the runway. When the PM questioned our altitude a second time; that's when I realized MISHA was off the nose and we had departed 2000 ft.FMS mode awareness. I failed to ensure we were in VNAV and I blindly followed the flight directors. I also should have immediately scrutinized our altitude when the PM first alerted that we were low. I also will not accept a visual approach inside the FAF unless we are certain where we are and that our altitude is appropriate.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.