B737 crew got a GPWS warning when on vectors at boi.

Attributes
ACN	429442
Time
Date	199902
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : iboi airport : boi
State Reference	ID
Altitude	msl bound lower : 6800 msl bound upper : 8000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Navigation In Use	Other
Flight Phase	descent other
Route In Use	arrival other enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 200 flight time total : 7000 flight time type : 1500
ASRS Report	429442
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial
Events
Anomaly	other anomaly other other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	other other
Consequence	Other
Supplementary
Air Traffic Incident	other
Situations
ATC Facility	procedure or policy : unspecified

Narrative:

While flying the approach to the localizer back course runway 28L at boise, we were being vectored to the final approach course while descending to the assigned 6800 ft altitude. Our path over the ground took us to the 20 DME radar fix, where there is 5360 ft terrain. Our descent rate (approximately 1000 FPM) and the lateral closure rate triggered the GPWS 'terrain' warning. I executed an immediate missed approach, intercepted the localizer, climbed to 8000 ft MSL and requested vectors for another approach, which was conducted without incident. Recommendations: change the vector altitude to 7500 ft, or even 8000 ft MSL for the 20 DME to 15 DME transition segment. Provide cautionary note regarding possible GPWS warning if altitudes are not changed. Revise controller procedures to vector aircraft inside of the 20 DME fix.

Original NASA ASRS Text

Title: B737 CREW GOT A GPWS WARNING WHEN ON VECTORS AT BOI.

Narrative: WHILE FLYING THE APCH TO THE LOC BACK COURSE RWY 28L AT BOISE, WE WERE BEING VECTORED TO THE FINAL APCH COURSE WHILE DSNDING TO THE ASSIGNED 6800 FT ALT. OUR PATH OVER THE GND TOOK US TO THE 20 DME RADAR FIX, WHERE THERE IS 5360 FT TERRAIN. OUR DSCNT RATE (APPROX 1000 FPM) AND THE LATERAL CLOSURE RATE TRIGGERED THE GPWS 'TERRAIN' WARNING. I EXECUTED AN IMMEDIATE MISSED APCH, INTERCEPTED THE LOC, CLBED TO 8000 FT MSL AND REQUESTED VECTORS FOR ANOTHER APCH, WHICH WAS CONDUCTED WITHOUT INCIDENT. RECOMMENDATIONS: CHANGE THE VECTOR ALT TO 7500 FT, OR EVEN 8000 FT MSL FOR THE 20 DME TO 15 DME TRANSITION SEGMENT. PROVIDE CAUTIONARY NOTE REGARDING POSSIBLE GPWS WARNING IF ALTS ARE NOT CHANGED. REVISE CTLR PROCS TO VECTOR ACFT INSIDE OF THE 20 DME FIX.

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.