B737NG flight crew reported receiving a low altitude alert from tower on approach to sfo.

Attributes
ACN	1732183
Time
Date	202003
Local Time Of Day	0601-1200
Place
Locale Reference	SFO.Airport
State Reference	CA
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B737 Next Generation Undifferentiated
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Route In Use	Visual Approach
Flight Plan	IFR
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 123 Flight Crew Type 1735
Person 2
Function	First Officer Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 159 Flight Crew Type 544
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Inflight Event / Encounter CFTT / CFIT

Narrative:

We were established on the sfo FMS bridge visual rwy 28R crossing the F101D fix (4.4 nm sfo) when the sfo tower controller on 120.5 issued a low altitude alert and told us that the altimeter setting was 29.94. I crossed checked the altitude and it showed us at 890' msl which was 310' below the published altitude at F101D. The first officer was the pilot flying with the autopilot engaged with VNAV/LNAV. Immediately upon hearing the low altitude alert from the sfo tower controller the first officer disconnected the autopilot; added power and began a climb to 1200 ft msl the at or above published altitude at F101D. VNAV path was annunciated on the FMA but was not captured at F101D. The tower controller queried me about the low altitude alert and said that he was going to contact engineering since we were the second aircraft in a row to set off the low altitude alert at the same point. I told the tower controller that we were flying the visual approach with the autopilot engaged and didn't catch the low altitude crossing. Since the first officer recovered/repaired the error we continued to a safe landing in compliance with the stabilized approach criteria.

Original NASA ASRS Text

Title: B737NG flight crew reported receiving a low altitude alert from Tower on approach to SFO.

Narrative: We were established on the SFO FMS Bridge Visual Rwy 28R crossing the F101D fix (4.4 nm SFO) when the SFO Tower Controller on 120.5 issued a low altitude alert and told us that the altimeter setting was 29.94. I crossed checked the altitude and it showed us at 890' msl which was 310' below the published altitude at F101D. The First Officer was the Pilot Flying with the autopilot engaged with VNAV/LNAV. Immediately upon hearing the low altitude alert from the SFO Tower Controller the First Officer disconnected the autopilot; added power and began a climb to 1200 ft msl the at or above published altitude at F101D. VNAV Path was annunciated on the FMA but was not captured at F101D. The Tower Controller queried me about the low altitude alert and said that he was going to contact engineering since we were the second aircraft in a row to set off the low altitude alert at the same point. I told the Tower Controller that we were flying the visual approach with the autopilot engaged and didn't catch the low altitude crossing. Since the First Officer recovered/repaired the error we continued to a safe landing in compliance with the stabilized approach criteria.

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.