Narrative:

Boarding, pushback, and taxi out were normal. During taxi out, ramp control advised that a new ATIS was in effect, with a new altimeter setting and windshear advisories. At that time I was briefing the takeoff, so I added the key details involved in a windshear recovery to my brief. The winds had not been noticeably gusty during my preflight, nor were they reported gusty on the ATIS, so I expected no significant problems on takeoff. We did notice that the aircraft in front of us took an exceptionally long takeoff roll. We attributed this to the aircraft having a heavy load, however, and did not correlate it with the windshear advisory until later. The aircraft did not make any report of windshear that we heard. The initial part of the takeoff roll was normal. Acceleration seemed normal. When the captain called out 'V1,' I glanced at my airspeed indicator and I read 112 KTS. Normally, our airline calls V1 5 KTS before actually reaching V1 to account for reaction time. Our V1 for this takeoff was 129 KTS, and I suspected at the time that the captain had elected to 'go' earlier than normal for some reason which I did not know at the time. Discussing the event later, I found out that the airspeed had decayed from V1 5 KTS (124 KTS ) to 112 KTS due to the windshear. The captain then mentioned something to the effect of 'bit of a stagnation there' and I could also tell that our airspeed was stagnating significantly. About then, the audible warning 'windshear' came on, along with the red windshear warning lights on the glareshield. I commanded 'firewall thrust' and simultaneously saw that we were accelerating again, although slowly. I kept the nosewheel on the runway longer than normal as we had plenty of runway. I do not know at what point on the runway we reached rotation speed. The captain had also pressed the toga switches so I followed the flyout guidance on the flight director. We maintained our confign until we agreed we were clearly out of danger and climbing rapidly, at which time I commanded 'gear up.' the captain raised the gear and reduced the thrust back to climb power and we began our after takeoff procedures. We advised the tower that we had received a 'windshear warning' on takeoff. They responded by asking us to verify that we had received a 'windshear caution' and we corrected them that it was a 'windshear warning.' they then advised an aircraft taking the runway after us that we had received a 'windshear caution,' which seems to indicate that they did not understand the difference. (A 'windshear caution' is accompanied by a yellow indicator light and comes on in the presence of a performance-increasing windshear, a 'windshear warning' has a red indicator light and means there is a performance-decreasing windshear and is much more serious.) we contacted departure and reviewed our post-action procedures for windshear encounters. The flight manual said something to the effect of 'return to normal flight,' so we continued to our destination of msy and advised the company via ACARS of the event. They asked for the time in firewall thrust (about 15 seconds), the outside air temperature (14 degrees C), and the maximum egt (neither of us noticed that parameter since we had other priorities in mind). After landing in msy, the contract mechanic had us take the aircraft out for a rest run of the engines and we then received a maintenance ferry permit to return the aircraft to clt for removal of the engine data recorders. The biggest difference I noticed in this event when compared to the simulator windshear scenario is that as we exited the windshear, performance returned more slowly and less dramatically than it does in the simulator. Otherwise (particularly with respect to the airspeed indications and takeoff roll increase), the simulator scenario was very similar to the actual event.

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Original NASA ASRS Text

Title: B737 CREW ENCOUNTERED MODERATE WINDSHEAR ON TKOF.

Narrative: BOARDING, PUSHBACK, AND TAXI OUT WERE NORMAL. DURING TAXI OUT, RAMP CTL ADVISED THAT A NEW ATIS WAS IN EFFECT, WITH A NEW ALTIMETER SETTING AND WINDSHEAR ADVISORIES. AT THAT TIME I WAS BRIEFING THE TKOF, SO I ADDED THE KEY DETAILS INVOLVED IN A WINDSHEAR RECOVERY TO MY BRIEF. THE WINDS HAD NOT BEEN NOTICEABLY GUSTY DURING MY PREFLT, NOR WERE THEY RPTED GUSTY ON THE ATIS, SO I EXPECTED NO SIGNIFICANT PROBS ON TKOF. WE DID NOTICE THAT THE ACFT IN FRONT OF US TOOK AN EXCEPTIONALLY LONG TKOF ROLL. WE ATTRIBUTED THIS TO THE ACFT HAVING A HVY LOAD, HOWEVER, AND DID NOT CORRELATE IT WITH THE WINDSHEAR ADVISORY UNTIL LATER. THE ACFT DID NOT MAKE ANY RPT OF WINDSHEAR THAT WE HEARD. THE INITIAL PART OF THE TKOF ROLL WAS NORMAL. ACCELERATION SEEMED NORMAL. WHEN THE CAPT CALLED OUT 'V1,' I GLANCED AT MY AIRSPD INDICATOR AND I READ 112 KTS. NORMALLY, OUR AIRLINE CALLS V1 5 KTS BEFORE ACTUALLY REACHING V1 TO ACCOUNT FOR REACTION TIME. OUR V1 FOR THIS TKOF WAS 129 KTS, AND I SUSPECTED AT THE TIME THAT THE CAPT HAD ELECTED TO 'GO' EARLIER THAN NORMAL FOR SOME REASON WHICH I DID NOT KNOW AT THE TIME. DISCUSSING THE EVENT LATER, I FOUND OUT THAT THE AIRSPD HAD DECAYED FROM V1 5 KTS (124 KTS ) TO 112 KTS DUE TO THE WINDSHEAR. THE CAPT THEN MENTIONED SOMETHING TO THE EFFECT OF 'BIT OF A STAGNATION THERE' AND I COULD ALSO TELL THAT OUR AIRSPD WAS STAGNATING SIGNIFICANTLY. ABOUT THEN, THE AUDIBLE WARNING 'WINDSHEAR' CAME ON, ALONG WITH THE RED WINDSHEAR WARNING LIGHTS ON THE GLARESHIELD. I COMMANDED 'FIREWALL THRUST' AND SIMULTANEOUSLY SAW THAT WE WERE ACCELERATING AGAIN, ALTHOUGH SLOWLY. I KEPT THE NOSEWHEEL ON THE RWY LONGER THAN NORMAL AS WE HAD PLENTY OF RWY. I DO NOT KNOW AT WHAT POINT ON THE RWY WE REACHED ROTATION SPD. THE CAPT HAD ALSO PRESSED THE TOGA SWITCHES SO I FOLLOWED THE FLYOUT GUIDANCE ON THE FLT DIRECTOR. WE MAINTAINED OUR CONFIGN UNTIL WE AGREED WE WERE CLRLY OUT OF DANGER AND CLBING RAPIDLY, AT WHICH TIME I COMMANDED 'GEAR UP.' THE CAPT RAISED THE GEAR AND REDUCED THE THRUST BACK TO CLB PWR AND WE BEGAN OUR AFTER TKOF PROCS. WE ADVISED THE TWR THAT WE HAD RECEIVED A 'WINDSHEAR WARNING' ON TKOF. THEY RESPONDED BY ASKING US TO VERIFY THAT WE HAD RECEIVED A 'WINDSHEAR CAUTION' AND WE CORRECTED THEM THAT IT WAS A 'WINDSHEAR WARNING.' THEY THEN ADVISED AN ACFT TAKING THE RWY AFTER US THAT WE HAD RECEIVED A 'WINDSHEAR CAUTION,' WHICH SEEMS TO INDICATE THAT THEY DID NOT UNDERSTAND THE DIFFERENCE. (A 'WINDSHEAR CAUTION' IS ACCOMPANIED BY A YELLOW INDICATOR LIGHT AND COMES ON IN THE PRESENCE OF A PERFORMANCE-INCREASING WINDSHEAR, A 'WINDSHEAR WARNING' HAS A RED INDICATOR LIGHT AND MEANS THERE IS A PERFORMANCE-DECREASING WINDSHEAR AND IS MUCH MORE SERIOUS.) WE CONTACTED DEP AND REVIEWED OUR POST-ACTION PROCS FOR WINDSHEAR ENCOUNTERS. THE FLT MANUAL SAID SOMETHING TO THE EFFECT OF 'RETURN TO NORMAL FLT,' SO WE CONTINUED TO OUR DEST OF MSY AND ADVISED THE COMPANY VIA ACARS OF THE EVENT. THEY ASKED FOR THE TIME IN FIREWALL THRUST (ABOUT 15 SECONDS), THE OUTSIDE AIR TEMP (14 DEGS C), AND THE MAX EGT (NEITHER OF US NOTICED THAT PARAMETER SINCE WE HAD OTHER PRIORITIES IN MIND). AFTER LNDG IN MSY, THE CONTRACT MECH HAD US TAKE THE ACFT OUT FOR A REST RUN OF THE ENGS AND WE THEN RECEIVED A MAINT FERRY PERMIT TO RETURN THE ACFT TO CLT FOR REMOVAL OF THE ENG DATA RECORDERS. THE BIGGEST DIFFERENCE I NOTICED IN THIS EVENT WHEN COMPARED TO THE SIMULATOR WINDSHEAR SCENARIO IS THAT AS WE EXITED THE WINDSHEAR, PERFORMANCE RETURNED MORE SLOWLY AND LESS DRAMATICALLY THAN IT DOES IN THE SIMULATOR. OTHERWISE (PARTICULARLY WITH RESPECT TO THE AIRSPD INDICATIONS AND TKOF ROLL INCREASE), THE SIMULATOR SCENARIO WAS VERY SIMILAR TO THE ACTUAL EVENT.

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.