Narrative:

We were on an extended left base about 10 mi from the airport; and being vectored for the visual to runway 12R to create spacing on a preceding citation to same runway. On that vector we were outside of the downtown buildings of houston; and heading about 220 degrees. Just north of downtown; we called the preceding citation and airport in sight and were cleared for the visual approach. I selected 150 degrees for a heading in the autoplt MCP for an intercept heading and as we rolled into that heading; I mentally noted that we would fly over some of the downtown buildings on that heading; and that I had never done that before that I could recall. As we passed over the buildings; we heard 'terrain; terrain' from the aircraft GPWS system. I want to emphasize that the alert was exactly as described. Only about 1 second's worth of 'terrain; terrain' and no 'pull up' was emitted. I responded by disconnecting the autoplt and applying thrust; and started to initiate a go around. I was perplexed by the alert; wondering if it was a caution or warning because of the absence of a 'pull up.' about that time we joined the localizer for runway 12R and were at about 2200 ft MSL; which put us on a published section of an approach; and above the charted altitude; so I reduced thrust; configured and landed without further incident. This type of event is obviously a high priority issue; and as such; I have spent a lot of time discussing this and thinking about GPWS alerts. Still; when I heard the alert; I didn't have a 'gag reflex' to the alert; much like you have to a stick shaker or windshear warning. I feel we need to train our crews in the simulator to react to these GPWS alerts by being able to incorporate them into pt's or even pc's. There needs to be a way for a simulator operator to activate GPWS alerts and thereby having a crew hear the alert and then executing the proper response. Supplemental information from acn 721952: well; we all know what we're supposed to do. I think we were both surprised that we got any type of terrain warning over the city when we could plainly see the building beneath us and had been in the exact spot before with no terrain warning. Also the confusion as to whether it was a warning or caution also delayed any action. Not sure there is much you can do in this case. Going around would have been the textbook answer for sure; but much like getting a terrain warning at FL200; may not have been the best answer in this case.

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Original NASA ASRS Text

Title: A B737-300 VMC OVER DOWNTOWN HOU DID NOT INITIATE A GPWS ESCAPE MANEUVER AT THE TERRAIN WARNING BECAUSE THE OBSTACLES WERE CLRLY IN SIGHT.

Narrative: WE WERE ON AN EXTENDED L BASE ABOUT 10 MI FROM THE ARPT; AND BEING VECTORED FOR THE VISUAL TO RWY 12R TO CREATE SPACING ON A PRECEDING CITATION TO SAME RWY. ON THAT VECTOR WE WERE OUTSIDE OF THE DOWNTOWN BUILDINGS OF HOUSTON; AND HDG ABOUT 220 DEGS. JUST N OF DOWNTOWN; WE CALLED THE PRECEDING CITATION AND ARPT IN SIGHT AND WERE CLRED FOR THE VISUAL APCH. I SELECTED 150 DEGS FOR A HDG IN THE AUTOPLT MCP FOR AN INTERCEPT HDG AND AS WE ROLLED INTO THAT HDG; I MENTALLY NOTED THAT WE WOULD FLY OVER SOME OF THE DOWNTOWN BUILDINGS ON THAT HDG; AND THAT I HAD NEVER DONE THAT BEFORE THAT I COULD RECALL. AS WE PASSED OVER THE BUILDINGS; WE HEARD 'TERRAIN; TERRAIN' FROM THE ACFT GPWS SYS. I WANT TO EMPHASIZE THAT THE ALERT WAS EXACTLY AS DESCRIBED. ONLY ABOUT 1 SECOND'S WORTH OF 'TERRAIN; TERRAIN' AND NO 'PULL UP' WAS EMITTED. I RESPONDED BY DISCONNECTING THE AUTOPLT AND APPLYING THRUST; AND STARTED TO INITIATE A GAR. I WAS PERPLEXED BY THE ALERT; WONDERING IF IT WAS A CAUTION OR WARNING BECAUSE OF THE ABSENCE OF A 'PULL UP.' ABOUT THAT TIME WE JOINED THE LOC FOR RWY 12R AND WERE AT ABOUT 2200 FT MSL; WHICH PUT US ON A PUBLISHED SECTION OF AN APCH; AND ABOVE THE CHARTED ALT; SO I REDUCED THRUST; CONFIGURED AND LANDED WITHOUT FURTHER INCIDENT. THIS TYPE OF EVENT IS OBVIOUSLY A HIGH PRIORITY ISSUE; AND AS SUCH; I HAVE SPENT A LOT OF TIME DISCUSSING THIS AND THINKING ABOUT GPWS ALERTS. STILL; WHEN I HEARD THE ALERT; I DIDN'T HAVE A 'GAG REFLEX' TO THE ALERT; MUCH LIKE YOU HAVE TO A STICK SHAKER OR WINDSHEAR WARNING. I FEEL WE NEED TO TRAIN OUR CREWS IN THE SIMULATOR TO REACT TO THESE GPWS ALERTS BY BEING ABLE TO INCORPORATE THEM INTO PT'S OR EVEN PC'S. THERE NEEDS TO BE A WAY FOR A SIMULATOR OPERATOR TO ACTIVATE GPWS ALERTS AND THEREBY HAVING A CREW HEAR THE ALERT AND THEN EXECUTING THE PROPER RESPONSE. SUPPLEMENTAL INFO FROM ACN 721952: WELL; WE ALL KNOW WHAT WE'RE SUPPOSED TO DO. I THINK WE WERE BOTH SURPRISED THAT WE GOT ANY TYPE OF TERRAIN WARNING OVER THE CITY WHEN WE COULD PLAINLY SEE THE BUILDING BENEATH US AND HAD BEEN IN THE EXACT SPOT BEFORE WITH NO TERRAIN WARNING. ALSO THE CONFUSION AS TO WHETHER IT WAS A WARNING OR CAUTION ALSO DELAYED ANY ACTION. NOT SURE THERE IS MUCH YOU CAN DO IN THIS CASE. GOING AROUND WOULD HAVE BEEN THE TEXTBOOK ANSWER FOR SURE; BUT MUCH LIKE GETTING A TERRAIN WARNING AT FL200; MAY NOT HAVE BEEN THE BEST ANSWER IN THIS CASE.

Data retrieved from NASA's ASRS site as of January 2009 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.