Narrative:

I was the PF and my first officer was the PNF. There were some isolated thunderstorms and rain showers northwest of the field. It was mostly clear; but hazy with visibility greater than 6 mi at the field. Upon arrival in the mexico city terminal area; and preparing to fly the ILS/DME 2 runway 5R; mex approach control advised us that a previous aircraft had reported a 15 KT windshear on final to runway 5R and we were placed in a holding pattern over smo VOR. While in the first turn in holding; we were asked if we would accept the approach to runway 5R with those conditions with winds on the surface reported 15-20 KTS out of the north. After conferring with first officer; we said yes and were cleared for the approach to runway 5R. Inside smo; descending to 9700 ft; the aircraft was at 160 KIAS; flaps 3 degrees; gear up and I disconnected the autoplt and autothrottles for a manual turn to final and final approach. Just prior to turning final; approach control directed us to discontinue the approach; climb to 11000 ft and proceed direct to otumba (otu) VOR for an approach to runway 23L. Mex tower had decided to change runways. During the go around; I selected toga power to sequence the FMGC; and began a climb to 11000 ft. The first officer set 11000 ft on the FCU. He began to query approach about the identify for otu which was not on the approach chart. Also he asked about current conditions on the field; and was beginning to program the box for runway 23L. Approaching 11000 ft; we retracted flaps to 1 degree and selected 210 KTS on the speed. I pulled the throttles back to the climb detent; thinking that the autothrottles would engage; not realizing that I had disconnected them and they were not armed. Naturally; the speed began decrease below 210 KTS due to low thrust setting; approaching vls. First officer also saw speed decreasing towards vls and called airspeed as I was bringing the throttles back to toga to regain speed at 210 KTS. I stabilized at 11000 ft; flaps 1 degree and almost immediately began to get vectors for final to runway 23L. It appeared that we were going to get vectors for a relatively short final (inside of 10 mi) so I continued to hand fly. While on a right downwind; my first officer commented that there was a large wind/dust storm south of the field on his side of the airplane and that there was probably windshear in it. I could not see what he was talking about. Turning final inside of 10 mi; I began to configure the airplane and could also see the dust storm that my first officer pointed out again. At approximately 9500-10000 ft; we intercepted final approach course and GS at 160 KIAS selected; flaps 3 degrees; gear down. At that point; both of us were questioning the prudence of continuing approach as the large dust storm seemed to be moving north into our final approach path. As we were switched to tower; he was giving us clearance to land on runway 23L; I noticed an increasing rate of descent into the orange color on the vsi (I think about 2000 FPM) along with the encroaching wind storm and decided to discontinue the approach. At about the same time; we got a facility-generated 'windshear; windshear; windshear' warning; 1 or 2 sink rate warnings causing me to immediately begin the windshear recovery profile; by going to toga; and aggressively pulling nose up towards srs command bars. During the recovery maneuver; first officer saw a maximum rate of descent of 300 FPM; airspeed close to vls until windshear warning went away at greater than 1500 FPM rate of climb. During windshear and recovery; we both felt that we never went below 1000 ft AGL and that the windshear encounter lasted 10-15 seconds; hard to say for sure. Following the windshear recovery; we cleaned up aircraft to flaps 1 degree; gear up; speed 210 KTS autoplt/autothrottles on and climbed to 1100 ft where we were directed to a hold pattern over smo again. After reporting the windshear encounter; tower returned to landing on runway 5R/left. They were calling the winds at approach end of 5 KTS as calm to 10 KTS out of the north and gusting up to 40+ KTS at approach to runway 23. With the winds still so unstable on the field; 6900 pounds of fuel remaining; and after coordinating with dispatch; we elected to divert to our alternate of morelia (mlm). Diversion; refueling at mlm;and return to mex 3 hours later was uneventful.

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Original NASA ASRS Text

Title: A320 FLT CREW ENCOUNTERS WINDSHEAR ON THEIR SECOND APCH TO MMEX; FOLLOWED BY A DIVERSION TO THEIR ALTERNATE.

Narrative: I WAS THE PF AND MY FO WAS THE PNF. THERE WERE SOME ISOLATED TSTMS AND RAIN SHOWERS NW OF THE FIELD. IT WAS MOSTLY CLR; BUT HAZY WITH VISIBILITY GREATER THAN 6 MI AT THE FIELD. UPON ARR IN THE MEXICO CITY TERMINAL AREA; AND PREPARING TO FLY THE ILS/DME 2 RWY 5R; MEX APCH CTL ADVISED US THAT A PREVIOUS ACFT HAD RPTED A 15 KT WINDSHEAR ON FINAL TO RWY 5R AND WE WERE PLACED IN A HOLDING PATTERN OVER SMO VOR. WHILE IN THE FIRST TURN IN HOLDING; WE WERE ASKED IF WE WOULD ACCEPT THE APCH TO RWY 5R WITH THOSE CONDITIONS WITH WINDS ON THE SURFACE RPTED 15-20 KTS OUT OF THE N. AFTER CONFERRING WITH FO; WE SAID YES AND WERE CLRED FOR THE APCH TO RWY 5R. INSIDE SMO; DSNDING TO 9700 FT; THE ACFT WAS AT 160 KIAS; FLAPS 3 DEGS; GEAR UP AND I DISCONNECTED THE AUTOPLT AND AUTOTHROTTLES FOR A MANUAL TURN TO FINAL AND FINAL APCH. JUST PRIOR TO TURNING FINAL; APCH CTL DIRECTED US TO DISCONTINUE THE APCH; CLB TO 11000 FT AND PROCEED DIRECT TO OTUMBA (OTU) VOR FOR AN APCH TO RWY 23L. MEX TWR HAD DECIDED TO CHANGE RWYS. DURING THE GAR; I SELECTED TOGA PWR TO SEQUENCE THE FMGC; AND BEGAN A CLB TO 11000 FT. THE FO SET 11000 FT ON THE FCU. HE BEGAN TO QUERY APCH ABOUT THE IDENT FOR OTU WHICH WAS NOT ON THE APCH CHART. ALSO HE ASKED ABOUT CURRENT CONDITIONS ON THE FIELD; AND WAS BEGINNING TO PROGRAM THE BOX FOR RWY 23L. APCHING 11000 FT; WE RETRACTED FLAPS TO 1 DEG AND SELECTED 210 KTS ON THE SPD. I PULLED THE THROTTLES BACK TO THE CLB DETENT; THINKING THAT THE AUTOTHROTTLES WOULD ENGAGE; NOT REALIZING THAT I HAD DISCONNECTED THEM AND THEY WERE NOT ARMED. NATURALLY; THE SPD BEGAN DECREASE BELOW 210 KTS DUE TO LOW THRUST SETTING; APCHING VLS. FO ALSO SAW SPD DECREASING TOWARDS VLS AND CALLED AIRSPD AS I WAS BRINGING THE THROTTLES BACK TO TOGA TO REGAIN SPD AT 210 KTS. I STABILIZED AT 11000 FT; FLAPS 1 DEG AND ALMOST IMMEDIATELY BEGAN TO GET VECTORS FOR FINAL TO RWY 23L. IT APPEARED THAT WE WERE GOING TO GET VECTORS FOR A RELATIVELY SHORT FINAL (INSIDE OF 10 MI) SO I CONTINUED TO HAND FLY. WHILE ON A R DOWNWIND; MY FO COMMENTED THAT THERE WAS A LARGE WIND/DUST STORM S OF THE FIELD ON HIS SIDE OF THE AIRPLANE AND THAT THERE WAS PROBABLY WINDSHEAR IN IT. I COULD NOT SEE WHAT HE WAS TALKING ABOUT. TURNING FINAL INSIDE OF 10 MI; I BEGAN TO CONFIGURE THE AIRPLANE AND COULD ALSO SEE THE DUST STORM THAT MY FO POINTED OUT AGAIN. AT APPROX 9500-10000 FT; WE INTERCEPTED FINAL APCH COURSE AND GS AT 160 KIAS SELECTED; FLAPS 3 DEGS; GEAR DOWN. AT THAT POINT; BOTH OF US WERE QUESTIONING THE PRUDENCE OF CONTINUING APCH AS THE LARGE DUST STORM SEEMED TO BE MOVING N INTO OUR FINAL APCH PATH. AS WE WERE SWITCHED TO TWR; HE WAS GIVING US CLRNC TO LAND ON RWY 23L; I NOTICED AN INCREASING RATE OF DSCNT INTO THE ORANGE COLOR ON THE VSI (I THINK ABOUT 2000 FPM) ALONG WITH THE ENCROACHING WIND STORM AND DECIDED TO DISCONTINUE THE APCH. AT ABOUT THE SAME TIME; WE GOT A FAC-GENERATED 'WINDSHEAR; WINDSHEAR; WINDSHEAR' WARNING; 1 OR 2 SINK RATE WARNINGS CAUSING ME TO IMMEDIATELY BEGIN THE WINDSHEAR RECOVERY PROFILE; BY GOING TO TOGA; AND AGGRESSIVELY PULLING NOSE UP TOWARDS SRS COMMAND BARS. DURING THE RECOVERY MANEUVER; FO SAW A MAX RATE OF DSCNT OF 300 FPM; AIRSPD CLOSE TO VLS UNTIL WINDSHEAR WARNING WENT AWAY AT GREATER THAN 1500 FPM RATE OF CLB. DURING WINDSHEAR AND RECOVERY; WE BOTH FELT THAT WE NEVER WENT BELOW 1000 FT AGL AND THAT THE WINDSHEAR ENCOUNTER LASTED 10-15 SECONDS; HARD TO SAY FOR SURE. FOLLOWING THE WINDSHEAR RECOVERY; WE CLEANED UP ACFT TO FLAPS 1 DEG; GEAR UP; SPD 210 KTS AUTOPLT/AUTOTHROTTLES ON AND CLBED TO 1100 FT WHERE WE WERE DIRECTED TO A HOLD PATTERN OVER SMO AGAIN. AFTER RPTING THE WINDSHEAR ENCOUNTER; TWR RETURNED TO LNDG ON RWY 5R/L. THEY WERE CALLING THE WINDS AT APCH END OF 5 KTS AS CALM TO 10 KTS OUT OF THE N AND GUSTING UP TO 40+ KTS AT APCH TO RWY 23. WITH THE WINDS STILL SO UNSTABLE ON THE FIELD; 6900 LBS OF FUEL REMAINING; AND AFTER COORDINATING WITH DISPATCH; WE ELECTED TO DIVERT TO OUR ALTERNATE OF MORELIA (MLM). DIVERSION; REFUELING AT MLM;AND RETURN TO MEX 3 HRS LATER WAS UNEVENTFUL.

Data retrieved from NASA's ASRS site as of January 2009 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.