A319 crew had an egpws 'terrain terrain' warning on a visual approach to runway 29 at mso.

Attributes
ACN	629216
Time
Date	200408
Day	Sun
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : mso.airport
State Reference	MT
Altitude	msl single value : 8500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : geg.tracon
Operator	common carrier : air carrier
Make Model Name	A319
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : approach
Route In Use	approach : visual
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 225 flight time total : 13000 flight time type : 3000
ASRS Report	629216
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 250 flight time total : 1000 flight time type : 3000
ASRS Report	629470
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	aircraft equipment : gpws other flight crewa other flight crewb
Resolutory Action	none taken : anomaly accepted
Supplementary
Problem Areas	Environmental Factor
Primary Problem	Aircraft

Narrative:

Spokane approach issued vectors to visual approach for runway 29 at mso. While at 9000 ft MSL handed off to mso tower. Cleared to land straight in runway 29. Received single phrase 'terrain-terrain' while over the ridge to the east of mso, and also south of centerline over a low section ('saddle'). Epgws with terrain selected to navigation display, did not indicate 'amber terrain' at this point. Visually, we were safe. Warning was brief/momentary. No corrective maneuvering needed, as the valley was visible. Proceeded to land with normal descent rate. Supplemental information from acn 629470: descending for visual approach runway 29 mso, we received a 'terrain, terrain' GPWS warning. Visual conditions at the time with terrain clearance assured, so no corrective action necessary. Passing over ridgeline when warning occurred so warning may have been associated with sudden radio altimeter sensing the terrain.

Original NASA ASRS Text

Title: A319 CREW HAD AN EGPWS 'TERRAIN TERRAIN' WARNING ON A VISUAL APCH TO RWY 29 AT MSO.

Narrative: SPOKANE APCH ISSUED VECTORS TO VISUAL APCH FOR RWY 29 AT MSO. WHILE AT 9000 FT MSL HANDED OFF TO MSO TWR. CLRED TO LAND STRAIGHT IN RWY 29. RECEIVED SINGLE PHRASE 'TERRAIN-TERRAIN' WHILE OVER THE RIDGE TO THE E OF MSO, AND ALSO S OF CTRLINE OVER A LOW SECTION ('SADDLE'). EPGWS WITH TERRAIN SELECTED TO NAV DISPLAY, DID NOT INDICATE 'AMBER TERRAIN' AT THIS POINT. VISUALLY, WE WERE SAFE. WARNING WAS BRIEF/MOMENTARY. NO CORRECTIVE MANEUVERING NEEDED, AS THE VALLEY WAS VISIBLE. PROCEEDED TO LAND WITH NORMAL DSCNT RATE. SUPPLEMENTAL INFO FROM ACN 629470: DSNDING FOR VISUAL APCH RWY 29 MSO, WE RECEIVED A 'TERRAIN, TERRAIN' GPWS WARNING. VISUAL CONDITIONS AT THE TIME WITH TERRAIN CLRNC ASSURED, SO NO CORRECTIVE ACTION NECESSARY. PASSING OVER RIDGELINE WHEN WARNING OCCURRED SO WARNING MAY HAVE BEEN ASSOCIATED WITH SUDDEN RADIO ALTIMETER SENSING THE TERRAIN.

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.