Narrative:

Inbound to las on the cresso arrival. We were given a vector off of the arrival and a descent to 6100 ft MSL in preparation for a left base entry to a visual approach to runway 25L. While in level flight at 6100 ft MSL, we received a GPWS terrain warning. In compliance with our company procedures, I instructed the first officer to increase power and climb. We leveled at 6800 ft MSL after the terrain warning was silenced. Las approach control was concerned about MD80 traffic in a left downwind above us approaching from our 9 O'clock position. After instructing the first officer to climb, I informed las approach of the GPWS warning and climb. I maintained visual contact with the MD80 throughout the entire maneuver. We were subsequently cleared for a visual approach. In a phone conversation with the approach control supervisor, he said there was not a separation conflict with the MD80 but that he was concerned about the potential for one. He was also surprised that we received a GPWS warning since they vector numerous aircraft over the terrain in that area at 6100 ft MSL. I also explained that our company procedures require an immediate climb upon receiving a GPWS terrain warning at night or in IMC when the terrain is not in sight. After talking to our maintenance control, I wrote a maintenance discrepancy on the GPWS to have the system checked for proper operation. Since we were at the MVA of 6100 ft MSL, I feel that we were given an incorrect terrain warning.

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Original NASA ASRS Text

Title: B737-300 RECEIVED AN ERRONEOUS GPWS TERRAIN WARNING AND CLBED PER COMPANY PROCS. THERE WAS MD80 TFC ABOVE THEM AND ATC WAS CONCERNED ABOUT A POTENTIAL CONFLICT. NO TCASII WARNING RECEIVED. GPWS PERFORMANCE WAS WRITTEN UP IN THE LOGBOOK.

Narrative: INBOUND TO LAS ON THE CRESSO ARR. WE WERE GIVEN A VECTOR OFF OF THE ARR AND A DSCNT TO 6100 FT MSL IN PREPARATION FOR A L BASE ENTRY TO A VISUAL APCH TO RWY 25L. WHILE IN LEVEL FLT AT 6100 FT MSL, WE RECEIVED A GPWS TERRAIN WARNING. IN COMPLIANCE WITH OUR COMPANY PROCS, I INSTRUCTED THE FO TO INCREASE PWR AND CLB. WE LEVELED AT 6800 FT MSL AFTER THE TERRAIN WARNING WAS SILENCED. LAS APCH CTL WAS CONCERNED ABOUT MD80 TFC IN A L DOWNWIND ABOVE US APCHING FROM OUR 9 O'CLOCK POS. AFTER INSTRUCTING THE FO TO CLB, I INFORMED LAS APCH OF THE GPWS WARNING AND CLB. I MAINTAINED VISUAL CONTACT WITH THE MD80 THROUGHOUT THE ENTIRE MANEUVER. WE WERE SUBSEQUENTLY CLRED FOR A VISUAL APCH. IN A PHONE CONVERSATION WITH THE APCH CTL SUPVR, HE SAID THERE WAS NOT A SEPARATION CONFLICT WITH THE MD80 BUT THAT HE WAS CONCERNED ABOUT THE POTENTIAL FOR ONE. HE WAS ALSO SURPRISED THAT WE RECEIVED A GPWS WARNING SINCE THEY VECTOR NUMEROUS ACFT OVER THE TERRAIN IN THAT AREA AT 6100 FT MSL. I ALSO EXPLAINED THAT OUR COMPANY PROCS REQUIRE AN IMMEDIATE CLB UPON RECEIVING A GPWS TERRAIN WARNING AT NIGHT OR IN IMC WHEN THE TERRAIN IS NOT IN SIGHT. AFTER TALKING TO OUR MAINT CTL, I WROTE A MAINT DISCREPANCY ON THE GPWS TO HAVE THE SYS CHKED FOR PROPER OP. SINCE WE WERE AT THE MVA OF 6100 FT MSL, I FEEL THAT WE WERE GIVEN AN INCORRECT TERRAIN WARNING.

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.