An air carrier medium large transport got a GPWS warning 'terrain' at MVA over mountainous terrain.

Attributes
ACN	268075
Time
Date	199404
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : sjc
State Reference	CA
Altitude	msl bound lower : 5100 msl bound upper : 6000
Environment
Flight Conditions	IMC
Light	Dusk
Aircraft 1
Controlling Facilities	tracon : oak
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	climbout : intermediate altitude cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 10000 flight time type : 1000
ASRS Report	268075
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : ground less severe inflight encounter : weather non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

While on radar vectors southwest of sjc (right downwind runway 12) at 5100 ft MSL assigned (level flight) we got a GPWS warning (we were in IMC). My copilot followed SOP and climbed. I advised ATC of our departure from assigned altitude and requested 6000 ft MSL. We leveled at 6000 ft and remainder of flight to sjc was uneventful. In discussion with bay approach after flight, I learned it was not uncommon to get GPWS alerts while being vectored at minimum vectoring altitudes over this area of high terrain. It seems that if approach knows they get an occasional GPWS when they vector at 5100 ft, they would discontinue this practice. I know it would have made my day easier!

Original NASA ASRS Text

Title: AN ACR MLG GOT A GPWS WARNING 'TERRAIN' AT MVA OVER MOUNTAINOUS TERRAIN.

Narrative: WHILE ON RADAR VECTORS SW OF SJC (R DOWNWIND RWY 12) AT 5100 FT MSL ASSIGNED (LEVEL FLT) WE GOT A GPWS WARNING (WE WERE IN IMC). MY COPLT FOLLOWED SOP AND CLBED. I ADVISED ATC OF OUR DEP FROM ASSIGNED ALT AND REQUESTED 6000 FT MSL. WE LEVELED AT 6000 FT AND REMAINDER OF FLT TO SJC WAS UNEVENTFUL. IN DISCUSSION WITH BAY APCH AFTER FLT, I LEARNED IT WAS NOT UNCOMMON TO GET GPWS ALERTS WHILE BEING VECTORED AT MINIMUM VECTORING ALTS OVER THIS AREA OF HIGH TERRAIN. IT SEEMS THAT IF APCH KNOWS THEY GET AN OCCASIONAL GPWS WHEN THEY VECTOR AT 5100 FT, THEY WOULD DISCONTINUE THIS PRACTICE. I KNOW IT WOULD HAVE MADE MY DAY EASIER!

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.