Date: 201202
Local time of day: 1801-2400
Location: SAN.Airport, CA
Flight conditions: Mixed
Light: Night
Aircraft: B737-300
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B SAN
ATC / advisory: TRACON SCT
Aircraft component: GPWS
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Confusion; Human-Machine Interface
Second reporter function: Pilot Flying; First Officer
Anomaly: Aircraft Equipment Problem Less Severe; Inflight Event / Encounter CFTT / CFIT
Detector: Automation Aircraft Terrain Warning; Person Flight Crew
When detected: In-flight
Result: General None Reported / Taken
Contributing factors: Aircraft; Environment - Non Weather Related
Primary problem: Ambiguous

Narrative: While being vectored to LOC 27 by SAN Approach Control; we received an abbreviated Terrain Warning. We were in a turn to a 240 heading to intercept 27 LOC and descending to 4;000 FT MSL until established on final. Passing approximately 4;400 FT MSL; and in our right turn to final; we received an abbreviated 'Terrain; Terrain' EGPWS Warning. We were just north of course between OKAIN and VYYDA; approximately near the 2;709 FT Tower area. We were aware of the terrain; and for that reason the First Officer was in a gradual descent. In this particular aircraft; the warning messages over the speaker system are very loud; so when the EGPWS Warning occurred; it definitely got both of our attention. At that moment; I was identifying the LOC frequency with my head down focused on the COMM panel. I immediately reached for the controls; but realized the First Officer was still flying; so I stopped. He started to bring the power up and disconnected the autopilot; but the warning never continued and stopped prior to him accomplishing these tasks. Clear of the conflict; we both then verified our altitude and looked at the terrain monitoring system; which showed 1;700 FT as a safe altitude and all terrain on the scope was green. We continued the approach without incident. In this case; the system may have performed as required. Although; our only concern is that we were well above minimum vectoring altitude and in a slow descending turn. I'm sure that being in a descent; turning into the rising terrain and maybe even some GPS error all contributed to the warning. We just wanted to let you know about the situation so that others would be aware and/or in case this aircraft had any history of this kind of previous event. Again; we respected the EGPWS Warning and were prepared to perform the terrain avoidance maneuver since it was at night. We did not complete the initial part of the terrain avoidance maneuver because before we could do it; the Terrain Warning had stopped even prior to 'pull up' and terrain contact was no longer a factor. I think we do a very good job of highlighting these kinds of possible situations. Having flown into SAN over the last 12 years; having descended over that particular hill many times; and knowing it was there even at that moment; unexpected warnings do occur and every now and then we need to be made aware of these possible events. In the event; this was an erroneous EGPWS Warning do to software or GPS issues. We just wanted to highlight the aircraft in case it has had previous unexplained events.


Second narrative: I was the pilot flying on downwind vectors for the LOC 27 SAN abeam OKAIN in a slow descent above scattered/few clouds. Just prior to base turn; I noticed the lights to the right on top of a hill and crosschecked it with the known charted hilltop 2;709 FT; just north of VYDDA and Terrain display of 2;800 FT. I am writing this up more as an informational report. We certainly believed terrain contact was no longer (or ever really) a factor and continued the approach. Check on the GPWS logic; perhaps a note on the 10-7 or approach chart.


Synopsis: A B737-300 crew reported a partial EGPWS TERRAIN warning at 4;400 FT near a charted 2;709 FT hilltop north of the SAN LOC 27 VYDDA intersection while the aircraft was on profile and in a slight descent.