GPWS warning on approach.

Attributes
ACN	294737
Time
Date	199501
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : hpn
State Reference	NY
Altitude	msl bound lower : 2000 msl bound upper : 2300
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : n90 tower : hhi
Operator	common carrier : air carrier
Make Model Name	B737-500
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 210 flight time total : 8000 flight time type : 5000
ASRS Report	294737
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action other other
Consequence	Other
Supplementary
Air Traffic Incident	other

Narrative:

We were cleared for the approach approximately 6-7 mi from hester, the OM, just as we were about to fully configure for landing, we heard 'terrain, terrain' from our GPWS. We performed the emergency procedure (immediate climb at maximum power) and during the climb the GPWS warning changed to 'whoop, whoop, pull up.' warning ceased at about 3000 ft and we leveled off at 4000 ft. ATC was advised just prior to leveloff, which was as soon as possible given radio congestion. We were given vectors around for a normal approach and landing. At this time I can only speculate the reason for the GPWS warning. Our second approach was over the same airspace, but level instead of descending (level at 2000 ft versus descending to 2000 ft). Also, to avoid a re-run we were configured for landing as we passed the point where we got the warning. A technical review might show a mode of our GPWS would trigger the warning we received, given our altitude and confign. But we believe we were doing the approach 'by the numbers.'

Original NASA ASRS Text

Title: GPWS WARNING ON APCH.

Narrative: WE WERE CLRED FOR THE APCH APPROX 6-7 MI FROM HESTER, THE OM, JUST AS WE WERE ABOUT TO FULLY CONFIGURE FOR LNDG, WE HEARD 'TERRAIN, TERRAIN' FROM OUR GPWS. WE PERFORMED THE EMER PROC (IMMEDIATE CLB AT MAX PWR) AND DURING THE CLB THE GPWS WARNING CHANGED TO 'WHOOP, WHOOP, PULL UP.' WARNING CEASED AT ABOUT 3000 FT AND WE LEVELED OFF AT 4000 FT. ATC WAS ADVISED JUST PRIOR TO LEVELOFF, WHICH WAS ASAP GIVEN RADIO CONGESTION. WE WERE GIVEN VECTORS AROUND FOR A NORMAL APCH AND LNDG. AT THIS TIME I CAN ONLY SPECULATE THE REASON FOR THE GPWS WARNING. OUR SECOND APCH WAS OVER THE SAME AIRSPACE, BUT LEVEL INSTEAD OF DSNDING (LEVEL AT 2000 FT VERSUS DSNDING TO 2000 FT). ALSO, TO AVOID A RE-RUN WE WERE CONFIGURED FOR LNDG AS WE PASSED THE POINT WHERE WE GOT THE WARNING. A TECHNICAL REVIEW MIGHT SHOW A MODE OF OUR GPWS WOULD TRIGGER THE WARNING WE RECEIVED, GIVEN OUR ALT AND CONFIGN. BUT WE BELIEVE WE WERE DOING THE APCH 'BY THE NUMBERS.'

Data retrieved from NASA's ASRS site as of July 2007 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.