Narrative:

We were being vectored for an ILS approach at spokane. During the turn from base to dogleg while descending from 4700 ft to 4500 ft assigned, the GPWS sounded a terrain warning followed by a pull-up verbal command and light. We immediately executed a maximum power climb to minimum safe sector altitude and advised ATC. There was no near-by traffic on 'tsas' or reported by ATC. Once we confirmed with ATC we were clear of the terrain, we resumed the approach. During the original vector for the ILS, our radar showed only light rain in all directions. Visually, the precipitation alternated between snow and rain. No ice was accumulating on the windows. After landing, I discussed the event with the air traffic controllers. Their radar showed level 1 precipitation throughout that area except for a 3 mi diameter area of level 2 precipitation to our right front. As we made the left turn to dogleg, this near-by localized heavier area of precipitation at or near the freezing level may have been recognized as a solid object by the GPWS and caused the warning. Supplemental information from acn 530747: approach gave us vectors and descent to the ILS runway 21. The ILS and landing were uneventful. Points of interest: 1) the 'whoop, whoop' sound was never heard, just 'terrain, terrain, pull up, pull up.' 2) neither the captain nor first officer saw the radar altimeter top scale preset. 3) on the ground, approach stated that there was not terrain at that altitude and position to merit the warning and they felt a level 2 rain shower at our position had triggered the alert. 4) no aircraft malfunctions or anomalies noted. 5) no passenger on board -- ferry flight.

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Original NASA ASRS Text

Title: A B733 CREW, DSNDING INTO GEG, RECEIVED A GPWS WARNING, 'TOO LOW TERRAIN' WITH A 'PULL UP' COMMAND.

Narrative: WE WERE BEING VECTORED FOR AN ILS APCH AT SPOKANE. DURING THE TURN FROM BASE TO DOGLEG WHILE DSNDING FROM 4700 FT TO 4500 FT ASSIGNED, THE GPWS SOUNDED A TERRAIN WARNING FOLLOWED BY A PULL-UP VERBAL COMMAND AND LIGHT. WE IMMEDIATELY EXECUTED A MAX PWR CLB TO MINIMUM SAFE SECTOR ALT AND ADVISED ATC. THERE WAS NO NEAR-BY TFC ON 'TSAS' OR RPTED BY ATC. ONCE WE CONFIRMED WITH ATC WE WERE CLR OF THE TERRAIN, WE RESUMED THE APCH. DURING THE ORIGINAL VECTOR FOR THE ILS, OUR RADAR SHOWED ONLY LIGHT RAIN IN ALL DIRECTIONS. VISUALLY, THE PRECIP ALTERNATED BTWN SNOW AND RAIN. NO ICE WAS ACCUMULATING ON THE WINDOWS. AFTER LNDG, I DISCUSSED THE EVENT WITH THE AIR TFC CTLRS. THEIR RADAR SHOWED LEVEL 1 PRECIP THROUGHOUT THAT AREA EXCEPT FOR A 3 MI DIAMETER AREA OF LEVEL 2 PRECIP TO OUR R FRONT. AS WE MADE THE L TURN TO DOGLEG, THIS NEAR-BY LOCALIZED HEAVIER AREA OF PRECIP AT OR NEAR THE FREEZING LEVEL MAY HAVE BEEN RECOGNIZED AS A SOLID OBJECT BY THE GPWS AND CAUSED THE WARNING. SUPPLEMENTAL INFO FROM ACN 530747: APCH GAVE US VECTORS AND DSCNT TO THE ILS RWY 21. THE ILS AND LNDG WERE UNEVENTFUL. POINTS OF INTEREST: 1) THE 'WHOOP, WHOOP' SOUND WAS NEVER HEARD, JUST 'TERRAIN, TERRAIN, PULL UP, PULL UP.' 2) NEITHER THE CAPT NOR FO SAW THE RADAR ALTIMETER TOP SCALE PRESET. 3) ON THE GND, APCH STATED THAT THERE WAS NOT TERRAIN AT THAT ALT AND POS TO MERIT THE WARNING AND THEY FELT A LEVEL 2 RAIN SHOWER AT OUR POS HAD TRIGGERED THE ALERT. 4) NO ACFT MALFUNCTIONS OR ANOMALIES NOTED. 5) NO PAX ON BOARD -- FERRY FLT.

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.