Narrative:

We were on radar vectors for a visual approach to runway 19L at las. Our position was approximately 8 NM northeast of the airport, on a heading of 250 degrees, and at our assigned altitude of 5100 ft MSL. The airport was in sight, as was a ridgeline in front of us that appeared to be no factor. Just as I was reading back our visual approach clearance, we got a GPWS warning of 'whoop, whoop, pull up.' the radio altimeter tape moved rapidly from off scale to 1200 ft AGL and was slowly decreasing. Although I did not feel that ground contact was a factor (seeing the ridgeline well silhouetted against the city lights and moving lower in the windscreen), the captain (who was flying) elected to perform the GPWS escape maneuver. He went to firewall thrust and rotated to about 20 degrees nose up. After about 3-5 seconds, the warning ceased. Power was reduced and the nose lowered to level flight. I reported the GPWS warning to the approach controller, who responded saying, 'sometimes that happens out there. I'm not sure why.' just a wild guess on my part, but maybe it has something to do with the mountains and the MVA. We continued to an uneventful visual approach and landing on runway 19L. I believe that the combination of the MVA and rapidly rising terrain is what triggers the GPWS, even though the aircraft is well clear of the terrain and not descending. The use of firewall thrust while performing the escape maneuver may well result in a 3 engine change. This is a very costly result of a situation that could probably be avoided by establishing a higher MVA. Reporter states that the installed GPWS was not enhanced and that the escape maneuver was a 'knee jerk' reaction on the part of the captain. He further states that in the company special pages of commercial chart that the possibility of GPWS alerts are a possibility, however, this was not addressed in the descent and landing briefing.

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Original NASA ASRS Text

Title: B727 GPWS ALERT AT LAS.

Narrative: WE WERE ON RADAR VECTORS FOR A VISUAL APCH TO RWY 19L AT LAS. OUR POS WAS APPROX 8 NM NE OF THE ARPT, ON A HDG OF 250 DEGS, AND AT OUR ASSIGNED ALT OF 5100 FT MSL. THE ARPT WAS IN SIGHT, AS WAS A RIDGELINE IN FRONT OF US THAT APPEARED TO BE NO FACTOR. JUST AS I WAS READING BACK OUR VISUAL APCH CLRNC, WE GOT A GPWS WARNING OF 'WHOOP, WHOOP, PULL UP.' THE RADIO ALTIMETER TAPE MOVED RAPIDLY FROM OFF SCALE TO 1200 FT AGL AND WAS SLOWLY DECREASING. ALTHOUGH I DID NOT FEEL THAT GND CONTACT WAS A FACTOR (SEEING THE RIDGELINE WELL SILHOUETTED AGAINST THE CITY LIGHTS AND MOVING LOWER IN THE WINDSCREEN), THE CAPT (WHO WAS FLYING) ELECTED TO PERFORM THE GPWS ESCAPE MANEUVER. HE WENT TO FIREWALL THRUST AND ROTATED TO ABOUT 20 DEGS NOSE UP. AFTER ABOUT 3-5 SECONDS, THE WARNING CEASED. PWR WAS REDUCED AND THE NOSE LOWERED TO LEVEL FLT. I RPTED THE GPWS WARNING TO THE APCH CTLR, WHO RESPONDED SAYING, 'SOMETIMES THAT HAPPENS OUT THERE. I'M NOT SURE WHY.' JUST A WILD GUESS ON MY PART, BUT MAYBE IT HAS SOMETHING TO DO WITH THE MOUNTAINS AND THE MVA. WE CONTINUED TO AN UNEVENTFUL VISUAL APCH AND LNDG ON RWY 19L. I BELIEVE THAT THE COMBINATION OF THE MVA AND RAPIDLY RISING TERRAIN IS WHAT TRIGGERS THE GPWS, EVEN THOUGH THE ACFT IS WELL CLR OF THE TERRAIN AND NOT DSNDING. THE USE OF FIREWALL THRUST WHILE PERFORMING THE ESCAPE MANEUVER MAY WELL RESULT IN A 3 ENG CHANGE. THIS IS A VERY COSTLY RESULT OF A SIT THAT COULD PROBABLY BE AVOIDED BY ESTABLISHING A HIGHER MVA. RPTR STATES THAT THE INSTALLED GPWS WAS NOT ENHANCED AND THAT THE ESCAPE MANEUVER WAS A 'KNEE JERK' REACTION ON THE PART OF THE CAPT. HE FURTHER STATES THAT IN THE COMPANY SPECIAL PAGES OF COMMERCIAL CHART THAT THE POSSIBILITY OF GPWS ALERTS ARE A POSSIBILITY, HOWEVER, THIS WAS NOT ADDRESSED IN THE DSCNT AND LNDG BRIEFING.

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.