B757 FLT CREW ENCOUNTERS WINDSHEAR INDUCED LOSS OF INDICATED AIRSPD ON DEP FROM SNA. FEAR THEY MAY HAVE SET OFF NOISE MONITORS.

Narrative

DURING TAXI OUT AND WAIT FOR TKOF; WE LISTENED TO NUMEROUS ACFT DEPARTING RWY 19R AT SNA RPT A LOSS OF AIRSPD ON DEP AT ABOUT 1000 FT. THE SURFACE WINDS WERE RPTED AT 230 DEGS AT 10 KTS AS WE TOOK THE RWY. WE STILL PLANNED TO FLY THE MUSEL 6 NOISE ABATEMENT PROFILE OUT OF SNA WITH THE EXPECTATION THAT WE MAY HAVE TO ABANDON IT DUE TO AN AIRSPD LOSS. WE WERE A LIGHT AIRPLANE WITH ONLY ABOUT 85 PAX AND A TKOF GROSS OF 174000 LBS. WE WERE GIVEN TKOF CLRNC AT XA23Z. THE TKOF ROLL AND INITIAL CLB WERE NORMAL; BUT AT 700 FT WE HAD A RAPID AIRSPD LOSS OF 20-25 KTS AND AN ONBOARD WINDSHEAR WARNING. I IMMEDIATELY LOWERED THE NOSE TO 15 DEGS; AND WE STILL HAD MAX TKOF THRUST; SO I DID NOT FIREWALL THE THRUST; BUT I DID NOT CALL FOR VNAV AS WE PASSED 800 FT AS IS CALLED FOR ON THE NOISE ABATEMENT PROFILE FOR ORANGE COUNTY. THE AIRSPD LOSS WAS ONLY MOMENTARY; AS BY 1000 FT THE WINDS WERE STABLE FROM THE N AT ABOUT 35 KTS. I CALLED FOR VNAV AND FLEW THE REMAINDER OF THE DEP UNEVENTFULLY. WE MADE A RPT TO THE TWR THAT WE HAD THE AIRSPD LOSS. BY DELAYING OUR PWR REDUCTION DUE TO THE WINDSHEAR; WE MAY OR MAY NOT HAVE SET OFF THE NOISE MONITORS ON THE DEP END OF RWY 19R.