An air carrier being vectored to bfi runway 31L was given a descent to 4;200 ft and received a terra...

Narrative:

We were flying the glasr arrival into bfi. Around jaksn intersection we were vectored off the arrival on a 180 degree heading for runway 31L; and given a descent to 6;000 ft. Later ATC cleared us to descend to 4;200 ft. It was daytime and the visibility was at least 20 miles. We could see a hill ahead of us and could tell we would clear it by 1;000 ft or so. I was expecting a turn before we would fly over the hill. Just in case we would not get a turn I double checked the altimeter setting and the HSI map; it showed yellow and red starting 10 miles off to the left but only a few areas of green ahead. When we were directly over the hill at 4;200 ft we received one 'terrain terrain - pull up'. We could see that we were clear of the terrain and did not do the CFIT maneuver. We cleared the hill and towers on top by 1;000 ft flying level. Our location was about 10 miles north northeast of the lackr intersection.

Original NASA ASRS Text

Title: An Air Carrier being vectored to BFI Runway 31L was given a descent to 4;200 FT and received a TERRAIN TERRAIN - PULL UP warning 10 north northeast of LACKR Intersection but took no evasive action because the conditions were day; VMC.

Narrative: We were flying the GLASR arrival into BFI. Around JAKSN Intersection we were vectored off the arrival on a 180 degree heading for Runway 31L; and given a descent to 6;000 FT. Later ATC cleared us to descend to 4;200 FT. It was daytime and the visibility was at least 20 miles. We could see a hill ahead of us and could tell we would clear it by 1;000 FT or so. I was expecting a turn before we would fly over the hill. Just in case we would not get a turn I double checked the altimeter setting and the HSI map; it showed yellow and red starting 10 miles off to the left but only a few areas of green ahead. When we were directly over the hill at 4;200 FT we received one 'TERRAIN TERRAIN - PULL UP'. We could see that we were clear of the terrain and did not do the CFIT maneuver. We cleared the hill and towers on top by 1;000 FT flying level. Our location was about 10 miles north northeast of the LACKR Intersection.

Data retrieved from NASA's ASRS site as of July 2013 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.

Attributes
ACN	1077429
Time
Date	201303
Local Time Of Day	1801-2400
Place
Locale Reference	BFI.Airport
State Reference	WA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Large Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 121
Flight Phase	Descent Initial Approach
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Captain Pilot Not Flying
Experience	Flight Crew Last 90 Days 30 Flight Crew Total 13500 Flight Crew Type 6000
Events
Anomaly	ATC Issue All Types Deviation - Procedural Published Material / Policy Inflight Event / Encounter CFTT / CFIT

An air carrier being vectored to bfi runway 31L was given a descent to 4;200 ft and received a terrain terrain - pull up warning 10 north northeast of lackr intersection but took no evasive action because the conditions were day; VMC.