A B737-300 on approach to tul 18L from the west rcvd GPWS caution after descending early on a right ...

Attributes
ACN	761672
Time
Date	200711
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : tul.airport
State Reference	OK
Altitude	msl single value : 2400
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Route In Use	approach : visual
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 253
ASRS Report	761672
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 237
ASRS Report	761668
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : published procedure non adherence : company policies other anomaly
Independent Detector	aircraft equipment : gpws other flight crewa
Resolutory Action	flight crew : took evasive action
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

I was the PF. ATC brought us along the west side of tul for a night visual approach to runway 18L. After descending us to 4000 ft and still slightly southwest of the field; we reported the field in sight. We were then cleared for the visual runway 18L. We then descended to 2400 ft. At about 6-7 mi (DME from ILS) I started a right base turn. After established on the base leg; corrected for a strong wind out of the southwest. At this time I believe; I started a gradual descent (we were already at flaps 5 degrees) and somewhere between runway 18R and runway 18L; the GPWS caution obstacle warning sounded. I added power; started a fairly rapid climb (did not reconfigure as we were still flaps 5 degrees gear up) until the alert ended. (It only sounded the one time.) we then continued the approach and landed uneventfully. After the event; the first officer and I tried to figure out what obstacle caused the warning. We could find none that were charted at that distance or location (between runway 18R and runway 18L). Also; oddly; there was no low altitude warning from ATC. After 5 days of going over and over this in my head; I think I had spotty situational awareness to begin with and then it degraded further. I think I started a premature descent and what the GPWS saw as an obstacle was really terrain. The first officer afterwards said he was about to question my altitude based on radar altitude; but did not. I (we) had some crew personality issues that in hindsight I did not deal with effectively. Supplemental information from acn 761668: we were on the visual approach to runway 18L in tulsa. While on the right base to the runway at approximately 6 mi from the airport; we received a GPWS obstacle warning. As we received the warning; we were at approximately 1500 ft RA. We initiated a full power climb immediately to approximately 2500 ft on the RA. At this point all warnings were gone. We continued on the approach to a landing without further incident. I was on the sixth leg of my day coming off a reduced rest overnight; after a 14 hour 30 min duty day the day before. I should have been watching the PF more. To his credit; he responded without any delay to the GPWS warning.

Original NASA ASRS Text

Title: A B737-300 ON APCH TO TUL 18L FROM THE WEST RCVD GPWS CAUTION AFTER DSNDING EARLY ON A R BASE. NO OBSTACLE WAS SEEN AND PLT ERROR ASSUMED.

Narrative: I WAS THE PF. ATC BROUGHT US ALONG THE W SIDE OF TUL FOR A NIGHT VISUAL APCH TO RWY 18L. AFTER DSNDING US TO 4000 FT AND STILL SLIGHTLY SW OF THE FIELD; WE RPTED THE FIELD IN SIGHT. WE WERE THEN CLRED FOR THE VISUAL RWY 18L. WE THEN DSNDED TO 2400 FT. AT ABOUT 6-7 MI (DME FROM ILS) I STARTED A R BASE TURN. AFTER ESTABLISHED ON THE BASE LEG; CORRECTED FOR A STRONG WIND OUT OF THE SW. AT THIS TIME I BELIEVE; I STARTED A GRADUAL DSCNT (WE WERE ALREADY AT FLAPS 5 DEGS) AND SOMEWHERE BTWN RWY 18R AND RWY 18L; THE GPWS CAUTION OBSTACLE WARNING SOUNDED. I ADDED PWR; STARTED A FAIRLY RAPID CLB (DID NOT RECONFIGURE AS WE WERE STILL FLAPS 5 DEGS GEAR UP) UNTIL THE ALERT ENDED. (IT ONLY SOUNDED THE ONE TIME.) WE THEN CONTINUED THE APCH AND LANDED UNEVENTFULLY. AFTER THE EVENT; THE FO AND I TRIED TO FIGURE OUT WHAT OBSTACLE CAUSED THE WARNING. WE COULD FIND NONE THAT WERE CHARTED AT THAT DISTANCE OR LOCATION (BTWN RWY 18R AND RWY 18L). ALSO; ODDLY; THERE WAS NO LOW ALT WARNING FROM ATC. AFTER 5 DAYS OF GOING OVER AND OVER THIS IN MY HEAD; I THINK I HAD SPOTTY SITUATIONAL AWARENESS TO BEGIN WITH AND THEN IT DEGRADED FURTHER. I THINK I STARTED A PREMATURE DSCNT AND WHAT THE GPWS SAW AS AN OBSTACLE WAS REALLY TERRAIN. THE FO AFTERWARDS SAID HE WAS ABOUT TO QUESTION MY ALT BASED ON RADAR ALT; BUT DID NOT. I (WE) HAD SOME CREW PERSONALITY ISSUES THAT IN HINDSIGHT I DID NOT DEAL WITH EFFECTIVELY. SUPPLEMENTAL INFO FROM ACN 761668: WE WERE ON THE VISUAL APCH TO RWY 18L IN TULSA. WHILE ON THE R BASE TO THE RWY AT APPROX 6 MI FROM THE ARPT; WE RECEIVED A GPWS OBSTACLE WARNING. AS WE RECEIVED THE WARNING; WE WERE AT APPROX 1500 FT RA. WE INITIATED A FULL PWR CLB IMMEDIATELY TO APPROX 2500 FT ON THE RA. AT THIS POINT ALL WARNINGS WERE GONE. WE CONTINUED ON THE APCH TO A LNDG WITHOUT FURTHER INCIDENT. I WAS ON THE SIXTH LEG OF MY DAY COMING OFF A REDUCED REST OVERNIGHT; AFTER A 14 HR 30 MIN DUTY DAY THE DAY BEFORE. I SHOULD HAVE BEEN WATCHING THE PF MORE. TO HIS CREDIT; HE RESPONDED WITHOUT ANY DELAY TO THE GPWS WARNING.

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.

A B737-300 on approach to tul 18L from the west rcvd GPWS caution after descending early on a right base. No obstacle was seen and pilot error assumed.