A hyperactive GPWS causes an air carrier medium large transport to climb.

Attributes
ACN	303007
Time
Date	199504
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : san
State Reference	CA
Altitude	msl bound lower : 3800 msl bound upper : 4300
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : san tracon : ind
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	cruise other descent : approach
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
ASRS Report	303007
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	302775
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : became reoriented flight crew : returned to intended course or assigned course
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

We were being vectored for a localizer runway 27/visual approach at san. WX on the ATIS was 3500 ft broken, 10 mi visibility, wind 240 degree at 8 KTS. We were being stepped down by san approach control on a 250 degree heading and cleared to 4000 ft MSL. We were then cleared for the approach and cleared to intercept the localizer on our 250 degree heading and cleared to 3800 ft MSL until established on the localizer. On this heading, it appeared we would intercept the localizer very close to swatt/12.6 DME on localizer. I remember thinking that we might still be at 3800 ft until inside swatt where the published altitude is 3600 ft. Descent rate at this time was approximately 1000 FPM. Passing through 4000 ft with flaps 15 degrees and slowing from 200 KTS to 180 KTS, we received a GPWS terrain warning. Autoplt and autothrottle were disconnected and a climb established. First officer advised approach we were climbing due to GPWS terrain warning and response from approach was that MVA in our area was 3800 ft MSL. At this time we could see ground to the left and right of aircraft, but not immediately beneath or in front due to clouds. We climbed probably 400-500 ft until we broke out of clouds and could safely see in front of us. About this time we also intercepted the localizer and were able to continue the approach. We were cleared to tower frequency and continued and landed normally.

Original NASA ASRS Text

Title: A HYPERACTIVE GPWS CAUSES AN ACR MLG TO CLB.

Narrative: WE WERE BEING VECTORED FOR A LOC RWY 27/VISUAL APCH AT SAN. WX ON THE ATIS WAS 3500 FT BROKEN, 10 MI VISIBILITY, WIND 240 DEG AT 8 KTS. WE WERE BEING STEPPED DOWN BY SAN APCH CTL ON A 250 DEG HDG AND CLRED TO 4000 FT MSL. WE WERE THEN CLRED FOR THE APCH AND CLRED TO INTERCEPT THE LOC ON OUR 250 DEG HDG AND CLRED TO 3800 FT MSL UNTIL ESTABLISHED ON THE LOC. ON THIS HDG, IT APPEARED WE WOULD INTERCEPT THE LOC VERY CLOSE TO SWATT/12.6 DME ON LOC. I REMEMBER THINKING THAT WE MIGHT STILL BE AT 3800 FT UNTIL INSIDE SWATT WHERE THE PUBLISHED ALT IS 3600 FT. DSCNT RATE AT THIS TIME WAS APPROX 1000 FPM. PASSING THROUGH 4000 FT WITH FLAPS 15 DEGS AND SLOWING FROM 200 KTS TO 180 KTS, WE RECEIVED A GPWS TERRAIN WARNING. AUTOPLT AND AUTOTHROTTLE WERE DISCONNECTED AND A CLB ESTABLISHED. FO ADVISED APCH WE WERE CLBING DUE TO GPWS TERRAIN WARNING AND RESPONSE FROM APCH WAS THAT MVA IN OUR AREA WAS 3800 FT MSL. AT THIS TIME WE COULD SEE GND TO THE L AND R OF ACFT, BUT NOT IMMEDIATELY BENEATH OR IN FRONT DUE TO CLOUDS. WE CLBED PROBABLY 400-500 FT UNTIL WE BROKE OUT OF CLOUDS AND COULD SAFELY SEE IN FRONT OF US. ABOUT THIS TIME WE ALSO INTERCEPTED THE LOC AND WERE ABLE TO CONTINUE THE APCH. WE WERE CLRED TO TWR FREQ AND CONTINUED AND LANDED NORMALLY.

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.