An air carrier medium large transport had a false GPWS warning.

Attributes
ACN	251723
Time
Date	199309
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : den
State Reference	CO
Altitude	msl bound lower : 8500 msl bound upper : 12500
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : den
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : instrument
Experience	flight time last 90 days : 140 flight time total : 6200 flight time type : 140
ASRS Report	251723
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : flight engineer pilot : commercial pilot : atp
Experience	flight time last 90 days : 210 flight time total : 9600 flight time type : 2100
ASRS Report	252342
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot inflight encounter : weather non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	controller : issued new clearance flight crew : exited adverse environment flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Thunderstorms were in the area and rain was falling at time of takeoff from runway 8L. We were cleared for takeoff and directed to turn to 065 degree heading after takeoff. A normal maximum power takeoff was accomplished from runway 8L. Shortly after retracting flaps on heading 065 degrees, we entered heavy rain/turbulence. At approximately 8500 ft MSL, the aircraft's GPWS sounded, indicating terrain and stating 'pull up, pull up.' the captain immediately applied company procedure's maximum power and rotated to 15 degrees nose high. Although the altimeter was indicating a climb situation, the radar altimeter was decreasing indicating closure with terrain. Due to the noise level from the rain and the GPWS, communication both inside and outside the cockpit was extremely difficult. During this situation we exceeded our clearance altitude of 10000 ft MSL. By the time the GPWS warnings had ceased and we had leveled off, we were at 12500 ft MSL. Den departure was notified of our deviation and we were directed to climb to 13000 ft MSL. In hindsight, it appears that we had experienced a failure in the GPWS system with a false terrain indication. Due to the IFR/rain conditions, we were not able to immediately identify this.

Original NASA ASRS Text

Title: AN ACR MLG HAD A FALSE GPWS WARNING.

Narrative: TSTMS WERE IN THE AREA AND RAIN WAS FALLING AT TIME OF TKOF FROM RWY 8L. WE WERE CLRED FOR TKOF AND DIRECTED TO TURN TO 065 DEG HDG AFTER TKOF. A NORMAL MAX PWR TKOF WAS ACCOMPLISHED FROM RWY 8L. SHORTLY AFTER RETRACTING FLAPS ON HDG 065 DEGS, WE ENTERED HVY RAIN/TURB. AT APPROX 8500 FT MSL, THE ACFT'S GPWS SOUNDED, INDICATING TERRAIN AND STATING 'PULL UP, PULL UP.' THE CAPT IMMEDIATELY APPLIED COMPANY PROC'S MAX PWR AND ROTATED TO 15 DEGS NOSE HIGH. ALTHOUGH THE ALTIMETER WAS INDICATING A CLB SIT, THE RADAR ALTIMETER WAS DECREASING INDICATING CLOSURE WITH TERRAIN. DUE TO THE NOISE LEVEL FROM THE RAIN AND THE GPWS, COM BOTH INSIDE AND OUTSIDE THE COCKPIT WAS EXTREMELY DIFFICULT. DURING THIS SIT WE EXCEEDED OUR CLRNC ALT OF 10000 FT MSL. BY THE TIME THE GPWS WARNINGS HAD CEASED AND WE HAD LEVELED OFF, WE WERE AT 12500 FT MSL. DEN DEP WAS NOTIFIED OF OUR DEV AND WE WERE DIRECTED TO CLB TO 13000 FT MSL. IN HINDSIGHT, IT APPEARS THAT WE HAD EXPERIENCED A FAILURE IN THE GPWS SYS WITH A FALSE TERRAIN INDICATION. DUE TO THE IFR/RAIN CONDITIONS, WE WERE NOT ABLE TO IMMEDIATELY IDENT THIS.

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.