Date: 201907
Local time of day: 0601-1200
Location: SAN.Airport, CA
Light: Daylight
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Landing
Airspace: Class B SAN
ATC / advisory: Tower SAN
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Distraction; Communication Breakdown; Human-Machine Interface; Situational Awareness
Second reporter function: Pilot Not Flying; Captain
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Airport; Environment - Non Weather Related; Procedure; Human Factors
Primary problem: Airport

Narrative: Prior to visual approach into Runway 27 SAN; as part of brief; FO (First Officer) briefed the unusually steep 3.5 degree glide slope per the SAN [Instrument Procedure] and reviewed the Flight Safety Alert - SAN for Runway 27. He also discussed presence of parking garage obstacle. After good communications; both pilots felt 'In the green.'During visual approach; FO verbally noted 'Clear of parking garage obstacle' and that he was going slightly high on the PAPI; and then increased the aircraft sink rate to correct for being high. FO noted a momentary GPWS 'Sink Rate' audible caution; and stated 'Correcting'. Flight path was immediately corrected; sink rate call went away. Tower was also making a radio call to another aircraft. FO continued the visual approach and landed uneventfully.After the flight at the gate; during the debrief; the Captain brought up that he may have seen a 'Pull Up' red advisory but wasn't sure. It was very quick and when he looked at it; it went away. He had been considering directing a go-around; but did not. FO stated he did not hear any audible GPWS 'Pull Up' and was focused visually outside. Then they discussed that it may be possible that the ATC Tower communication may have blocked a GPWS warning; and if there had been an audible 'Pull Up'; it would have required a mandatory go-around.  As part of debrief; Crew reviewed how very loud a GPWS 'Pull Up' warning would be using the test function; and doesn't believe they could have missed it.Upon reviewing other resources such as the FRM radio altitude alerts; and QRH maneuvers; an audible caution 'Sink Rate' along with a red 'Pull Up' advisory on the PFD is the indication of what is considered an 'Additional GPWS Caution' and the proper response is just as was executed; to adjust flight path and continue if safe. This caution does not require a go-around. Crew discussed the confusion in the moment that may have been caused by the fact that a distracting red 'Pull Up' indication on the PFD is part of and considered an additional caution and not a warning. Finally; the Crew discussed submitting this report in the unlikely event they missed an audible 'Pull Up' warning which would be potentially unsafe.


Second narrative: FO (First Officer) briefed the RNP (Required Navigation Performance) Z to SAN [Runway] 27. He specifically mentioned the parking garage and 3.5 degree glide path. We discussed the possibility of an increased descent rate referenced in the Safety Alert in the [Instrument Procedure]; the visual conditions; and the parking garage. The approach was a little fast on airspeed and required a pitch correction to transition to the visual path.  The FO stated; 'There's the garage' and I looked up; outside; and saw a slightly high indication on the PAPI.  Just then we got a 'Sink Rate' caution and the FO responded with; 'Correcting'. The FO immediately corrected the aircraft pitch and then stated; 'We are clear of the garage;' and made a slight pitch over to correct the path. We immediately got another 'Sink Rate' caution. I looked inside and thought I saw a 'Pull Up' text on the panel. I went for the thrust levers and started to verbalize for a full power recovery. As I glanced at the instruments to verify; there was no message and the aural command had stopped within a fraction of a second. I looked out and we were on path; so I allowed the approach to continue. After landing; we debriefed the SAN Approach and discussed the slightly early and possible over correction to path. The FO mentioned his shifting the aim point. I asked the FO if he saw or heard any Pull Up Warning. He stated 'No'. There is a condition where a Pull Up text will appear without an audible warning when an excessive sink rate continues. I think that anytime a Pull Up text appears there should be an audible warning.


Synopsis: B737 flight crew reported a possible 'Pull Up' warning while responding to 'Sink Rate' warning during landing sequence. Crew continued landing successfully.