Narrative:

Briefed runway 35 departure prior to taxi out. On taxi out, saw winds were light and variable, we requested runway 17. Tower controller approved runway without comment. At takeoff position, controller cleared us for takeoff and instructed 'climb on course, maintain VFR, report leaving 12000 ft. After a normal takeoff, first officer referred back to runway 17 departure procedure which stated that if able to maintain VFR to minimum crossing altitude (11200 ft) climb on course (saltillo, mexico, 172 degree radial). Since we had been cleared this way by the tower controller and met the WX minimums necessary, we proceeded. At approximately 10300 ft, radio altimeter began to jump around followed by a brief GPWS terrain warning. We immediately initiated a maximum performance climb per our training. Note: we were exactly on the departure radial (172 degrees) when this occurred. Warning ceased immediately and radio altimeter returned to normal. We proceeded with a normal climb. At this point we are still not sure why GPWS warning activated. We followed the procedure exactly in a normal climb. Our takeoff weight was light (approximately 135000 pounds) and climb performance was very good. It is possible that this was false warning triggered by rough and irregular terrain. Suggest procedure at this airport be scrutinized to ensure safety. In addition at all airports with mountainous terrain in the vicinity, approach plates should include detailed orographic information. Callback conversation with reporter revealed the following information: reporter captain states that they may have been slightly off course from the 172 degree radial, and in reviewing the sectional chart of the slw area it was noted that a mountain at 10340 ft was approximately on the 150 degree radial at 12 mi. Both reporter and analyst who discussed the situation with him agreed that the likely cause of the GPWS was rapidly rising terrain in the vicinity of the mountain which the GPWS would sense as closure rate. Reporter recommends that a note be included in the departure procedure at slw to alert flcs to the high terrain to the southeast. Reporter also believes that the charts should be orographic as are many other approach plates in areas of mountainous terrain. Supplemental information from acn 378602: prior to takeoff, tower advised 'cleared takeoff, climb on course (172 degree radial) and maintain VFR.' takeoff and climb out was uneventful.

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Original NASA ASRS Text

Title: B727 ACFT ON CLBOUT FROM SALTILLO, MEXICO, AND ON THE 172 DEG RADIAL RECEIVED GPWS AT 10300 FT. FLC TOOK IMMEDIATE ACTION TO CLB. 'TERRAIN' WARNING WAS VERY SHORT.

Narrative: BRIEFED RWY 35 DEP PRIOR TO TAXI OUT. ON TAXI OUT, SAW WINDS WERE LIGHT AND VARIABLE, WE REQUESTED RWY 17. TWR CTLR APPROVED RWY WITHOUT COMMENT. AT TKOF POS, CTLR CLRED US FOR TKOF AND INSTRUCTED 'CLB ON COURSE, MAINTAIN VFR, RPT LEAVING 12000 FT. AFTER A NORMAL TKOF, FO REFERRED BACK TO RWY 17 DEP PROC WHICH STATED THAT IF ABLE TO MAINTAIN VFR TO MINIMUM XING ALT (11200 FT) CLB ON COURSE (SALTILLO, MEXICO, 172 DEG RADIAL). SINCE WE HAD BEEN CLRED THIS WAY BY THE TWR CTLR AND MET THE WX MINIMUMS NECESSARY, WE PROCEEDED. AT APPROX 10300 FT, RADIO ALTIMETER BEGAN TO JUMP AROUND FOLLOWED BY A BRIEF GPWS TERRAIN WARNING. WE IMMEDIATELY INITIATED A MAX PERFORMANCE CLB PER OUR TRAINING. NOTE: WE WERE EXACTLY ON THE DEP RADIAL (172 DEGS) WHEN THIS OCCURRED. WARNING CEASED IMMEDIATELY AND RADIO ALTIMETER RETURNED TO NORMAL. WE PROCEEDED WITH A NORMAL CLB. AT THIS POINT WE ARE STILL NOT SURE WHY GPWS WARNING ACTIVATED. WE FOLLOWED THE PROC EXACTLY IN A NORMAL CLB. OUR TKOF WT WAS LIGHT (APPROX 135000 LBS) AND CLB PERFORMANCE WAS VERY GOOD. IT IS POSSIBLE THAT THIS WAS FALSE WARNING TRIGGERED BY ROUGH AND IRREGULAR TERRAIN. SUGGEST PROC AT THIS ARPT BE SCRUTINIZED TO ENSURE SAFETY. IN ADDITION AT ALL ARPTS WITH MOUNTAINOUS TERRAIN IN THE VICINITY, APCH PLATES SHOULD INCLUDE DETAILED OROGRAPHIC INFO. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR CAPT STATES THAT THEY MAY HAVE BEEN SLIGHTLY OFF COURSE FROM THE 172 DEG RADIAL, AND IN REVIEWING THE SECTIONAL CHART OF THE SLW AREA IT WAS NOTED THAT A MOUNTAIN AT 10340 FT WAS APPROX ON THE 150 DEG RADIAL AT 12 MI. BOTH RPTR AND ANALYST WHO DISCUSSED THE SIT WITH HIM AGREED THAT THE LIKELY CAUSE OF THE GPWS WAS RAPIDLY RISING TERRAIN IN THE VICINITY OF THE MOUNTAIN WHICH THE GPWS WOULD SENSE AS CLOSURE RATE. RPTR RECOMMENDS THAT A NOTE BE INCLUDED IN THE DEP PROC AT SLW TO ALERT FLCS TO THE HIGH TERRAIN TO THE SE. RPTR ALSO BELIEVES THAT THE CHARTS SHOULD BE OROGRAPHIC AS ARE MANY OTHER APCH PLATES IN AREAS OF MOUNTAINOUS TERRAIN. SUPPLEMENTAL INFO FROM ACN 378602: PRIOR TO TKOF, TWR ADVISED 'CLRED TKOF, CLB ON COURSE (172 DEG RADIAL) AND MAINTAIN VFR.' TKOF AND CLBOUT WAS UNEVENTFUL.

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.