MD88 FLT CREW ENCOUNTERS WINDSHEAR ON FINAL AT DEN.

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ON FINAL APCH TO RWY 35R AT DEN; WE WERE VECTORED IN BEHIND A B777. THAT ACFT WAS ABOUT 6 MI IN FRONT OF US. (I DOUBLECHKED HIS RANGE ON TCAS TO VERIFY HE WAS NOT ON OUR SCREEN INSIDE THE 5 MI SCALE AS I HAVE ENCOUNTERED WAKE TURB FROM B777'S BEFORE.) THE FO WAS FLYING. THE APCH CTLR CLRED US FOR THE VISUAL APCH; TOLD US TO MAINTAIN 170 KTS TO FRONZ (FAF FOR RWY 35R); AND INSTRUCTED US TO SWITCH TO TWR. THERE WAS ALSO PARALLEL TFC AHEAD OF US FOR RWY 35L. UPON CONTACTING DEN TWR WE WERE CLRED TO LAND AND TOLD THE WINDS WERE 310 DEGS AT 5 KTS. (ATIS SAID WINDS WERE 060 DEGS AT 9 KTS; SCATTERED CLOUDS 10 MI VISIBILITY AND TEMP OF 96 DEGS; WITH VIRGA IN THE DISTANCE TO THE SW LLWS ADVISORIES IN EFFECT; AND THERE HAD BEEN A PIREP 35 NM N OF DENVER WITH LIGHT TO MODERATE TURB AT 8000 FT. OUR RIDE HAD BEEN MOSTLY SMOOTH SINCE DSNDING THROUGH LIGHT CHOP IN THE CLOUDS BTWN FL210-17000 FT. SEVERAL ACFT HAD LANDED BEFORE US ON BOTH RWYS 35R AND RWY 35L WITH NO MENTION OF ABNORMAL CONDITIONS. JUST PRIOR TO FRONZ WE BEGAN OUR LNDG CONFIGN. AS THE FLAPS WERE LOWERED TO 40 DEGS; THE L HYD QUANTITY LOW LEVEL LIGHT ILLUMINATED WITH AN INDICATION OF 4 QUARTS. WE WERE ON TRACK -- ON GS ON THE RWY 35R ILS WITH THE SPD DECREASING TOWARD THE TARGET OF 135 WHICH WAS VREF FLAPS 40 DEGS +5 KTS (BUG SPD BASED ON TWR CALLED WINDS FOR A 125;000 LB ACFT). (WE HAD BRIEFED TO DO A FLAP 40 DEG LNDG TO HELP REDUCE OUR GND SPD GIVEN HIGHER TAS AT A HIGH ALT ARPT.) AS I WAS EVALUATING THE L HYD SYS; I SAW THE RED LIGHT OF THE DECREASING PERFORMANCE WINDSHEAR ALERT SYS AND HEARD THE AURAL WARNING. WE WERE ABOUT 700 FT AGL AT THIS TIME. WE BOTH CALLED OUT 'WINDSHEAR' AND THE FO CALLED OUT TOGA PWR AND IMMEDIATELY ADVANCED THE THROTTLES AND PITCHED THE NOSE TO FOLLOW THE WINDSHEAR GUIDANCE. THE ACFT RESPONDED WELL AND I DON'T THINK WE WENT BELOW 400 FT AGL. ALT AND AIRSPD RECOVERED QUICKLY AS WE CLBED AND CONFIGURED FOR OUR MISSED APCH ALT OF 10000 FT MSL. THE FO SAID HE SAW A LOSS OF 15 KTS IN AIRSPD AS THE WINDSHEAR SYS ALERTED. I GAVE THE TWR A WINDSHEAR PIREP; TELLING THEM WE HAD A 15 KT LOSS OF AIRSPD ON FINAL. THE MECH LATER TOLD US THAT THE L HYD SYS WAS LEAKING FROM THE L THRUST REVERSER COUPLING IN THE L ENG PYLON. YES; UNFORTUNATELY; BOTH ENGS HAD BEEN OVER-BOOSTED REQUIRING A DOUBLE ENG CHANGE. DATA RECORDER INDICATED LOWEST ALT DURING WINDSHEAR RECOVERY WAS 432 FT AGL. LOOKING BACK AT THE WINDSHEAR EVENT; IT WAS OVER ABOUT AS FAST AS IT STARTED. IT DEFINITELY WAS NOT A SIMULATOR TYPE WINDSHEAR SIMULATION WITH AN EXTENDED ROLLERCOASTER RIDE. THE ACFT WAS UNDER CTL AT ALL TIMES. THE FO'S RESPONSE ON THE AFT CTLS WAS CORRECT; IMMEDIATE AND SMOOTH. THE PROGRESSIVE DECREASE IN ACFT PERFORMANCE WAS NOT ALLOWED TO CONTINUE DUE TO THE QUICK RECOGNITION AND REACTION BY THE FO IN CLOSE PROX TO THE GND. FO DID A GREAT JOB. I SUSPECT THAT WAKE TURB FROM THE B777 COMBINED WITH LCL CONDITIONS CAUSED THE WINDSHEAR WARNING SYS TO ACTIVATE.