Narrative:

I arrived at the aircraft first and started my standard routine. The captain arrived shortly after and told me that he had talked to dispatch and decided on changing the alternate to pit. I told him that I thought that was a real good idea and that I agreed with him completely. Release 2 reflected the new alternate and fuel burn. The climbout and cruise on our scheduled route of flight was uneventful. While enroute to bwi we pulled up the bwi ATIS reports frequently to keep abreast of any changing weather conditions or runway changes. I pulled up a report for bwi and showed it to the captain. It showed light rain with a gust front (gg) to the west of the airport. The captain remarked that it was fast moving at 60 KTS. I pulled up the landing weight data for bwi runway 15R to see if there were any field conditions that we needed to know about. There was none listed. I reviewed the notams and mentioned that there was nothing that concerned us. The captain briefed the approach; turn-off; go-around procedures; tuned and set up the navaids and we set our airspeed bugs for a flaps 25 approach and landing. The winds at bwi were something like 180 degrees; 8 KTS gusting to 17. Our ref speed was approximately 126 KTS plus a 14 KT addition = 140 KTS. Windshear advisories were listed on the bwi ATIS but that was to be expected with these gusty surface winds.about 100-150 miles from bwi I turned on the seatbelt sign and seated the passengers. We were now at a lower altitude; maybe 15;000 ft. The cloud tops from the weather was still below us; rough but not too threatening. We both had our weather radar switches turned on; mostly green with isolated yellow areas. No red at all. I made a PA directing the flight attendants to 'prepare for landing and remain seated' before we entered the cloud tops. Turbulence was mostly light chop and we both thought that maybe we seated the flight attendants way too early. Engine heat was turned on. At some point I pulled up another report for bwi. It showed the gust front still west of the airport but slightly closer. While listening to ATC we heard no pireps from any other aircraft or adverse advisories from approach control. So far it sounded like everyone was getting in to bwi with nothing more than a slightly bumpy ride. Closer in to bwi; approach control began to vector us for the ILS 15R approach and descended us to around 4;000 to 5;000 ft. ATC vectored us through the ILS centerline at almost a 90 degree angle; something like a 080 degree heading. Eventually ATC did direct an almost 180 degree turn to the right to intercept the ILS 15R and track the localizer inbound. We make the turn with the autopilot still on. I think ATC gave us a few minor vectors to shallow out the intercept angle. We could see on TCAS that there were a couple aircraft on final ahead of us but still no adverse weather reports at all. Only light chop. The captain and I were using two different scales on the weather radar; his was closer in; and mine was the next scale out so that we could cross check what each was seeing. Intercepted the localizer easily. The captain had already dialed the speed back to 180 KTS prior to the outer marker so the flaps had already been extended to 15 or 20. The captain called for the gear down and set the target speed of 140. I did and completed the final descent checklist. We were cleared for the approach; armed it and captured the glide slope. I set touchdown zone elevation and switched to tower. Flaps were extended to 25.I reported the outer marker to tower and I think they gave us landing clearance. The tower did make a remark that the winds were shifting at the airport. We were actually quite stabilized at this point with a little more than light chop and light to moderate rain. The weather radar still reflected mostly green with areas of yellow. There were some small patches of magenta turbulence dots on the weather radar ahead of us but we never saw any indications that would lead us to think that severe windshear lie just ahead. No aural or visual warnings from the pws (proximity warning system); nothing from approach control prior to their hand off to the tower or from the tower itself. What started slowly became an instant flash. First; the auto throttles began to advance and slow more than usual. Then; the airspeed began to accelerate and decrease about plus or minus 20 KTS. Having seen this scenario in the simulator we both knew what was beginning to happen. The captain made a quick decision at this point and remarked 'that's it I'm out of here; going around; flaps 20; positive climb; gear up; spin the altitude up.' I quickly complied. The captain clicked the autopilot off and hand flew the missed approach-soon to be-windshear recovery. I told tower that we were missed approach. I don't remember if I gave them the reason why; I was extremely focused on doing more important things at the moment. They instructed us to fly runway heading; climb and maintain 3;000 ft (4;000 ft).the windshear conditions persisted all the way up to our level off altitude and we began to fly out of it. During this first windshear event I would say that the airspeed fluctuations were about plus or minus 20-25 KTS. During the second event that occurred during our approach to runway 33L the airspeed variations were much more extreme. Once level; we cleaned the flaps up to 5; then 1; then up. Speed set to around 210 KTS. Tower said that they were now changing the airport around to runway 33L and would we like to do that? We said yes. I made a very quick PA informing the passengers of what just happened and that they were changing the airport around and that we were going to give it another try. The captain put the autopilot back on when things settled down. I told the captain to give me a minute to install the approach and extend it. He handled the radio calls; pulled up the ILS 33L approach plates and set the new ILS course. The vector around to runway 33L happened quickly. Once I finally finished installing and extended the runway centerline we were already in a base turn getting ready to intercept final. I quickly did an approach checklist. The captain called for extended flap settings as he slowed the aircraft down. We were told to intercept final; cleared for the ILS 33L approach. Again; the captain had the gear down with flaps set at 25 and very close to target speed as we crossed the outer marker (grafe at 1;500 ft MSL). Weather radar still showed about 60 percent green; 40 percent various yellow areas. None of the yellow areas appeared in a line; mostly patchy locations. No magenta turbulence areas at all this time. I think I had already switched over to tower and checked in with them when the second event occurred. I'm not sure but we may have been the first aircraft to get vectored around for the ILS 33L approach and ATC didn't have any information that they could advise us of yet. (The captain said in our debrief that one aircraft was indeed ahead of us).the very first thing I noticed was how rapidly the outside weather color went from a light to medium gray to almost black. Then in an instant; with no warning whatsoever; we were in a full microburst event. Things happened very quickly and it is hard to piece things together in the exact order that they occurred. Again; at the very first indication of unusual autothrottle movement and changing airspeed the captain quickly initiated a go-around. I set the flaps to 20; raised the gear; and spun the altitude up. I know the airspeed accelerated to nearly 240 KTS; and then dropped off to around 100; then back towards 240. I looked over at the captain and he was both pulling and pushing the yoke with major force trying to keep things under control. I reached down with my left hand and grabbed the autothrottles to try to stabilize their extreme movements while at the same time informing tower of our go-around. This time I know I did make the remark 'due to extreme windshear' to tower. I was well aware that we were over speeding the flaps during this whole event but things happened so quickly with myself working the autothrottles; informing tower; watching the airspeed fly through the roof one minute and then wondering if the airplane was going to stall the next that I couldn't process what to do (if anything) with the flaps quick enough. Again; no pws advisories or warnings at all. In hindsight we think that we were just one or two hundred feet above the 1;200 ft AGL altitude that the pws provides the verbal and visual indications. We climbed up to our assigned altitude of 3;000 or 4;000 ft MSL. It was everything the captain could do to try to keep the airplane anywhere close to our assigned altitude. I informed tower that we were just trying to hold altitude the best we could - plus or minus 500 ft. I also told the tower that we were plus or minus fifty KTS. I wanted to make sure the tower knew the severity of this weather condition to prevent vectoring anybody in just behind us. I took the liberty of setting a speed in the 'speed window' of the MCP that seemed best for all these conditions once we were somewhere near our assigned altitude. Once things began to settle down again the captain called for flaps 5; then 1; then up. We switched over to approach control and I advised them that we were going to proceed to our alternate. ATC gave us continued climbs and vectors onto an airway. During the climbout I sent dispatch a message informing them of our divert. Dispatch sent an ACARS message suggesting that we go to iad. The captain said 'no we're going to pit' which I completely agreed with. I know I thought to myself 'I sure don't want to even think of having to deal with another windshear issue again' at nearby iad. I sent in two maintenance messages. One for the flap overspeeds; the second for not receiving any pws windshear alerts or warnings even thought we were in a complete windshear and then microburst condition. Not even a windshear icon was displayed at any time. The remainder of the flight was uneventful.

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Original NASA ASRS Text

Title: A B757 flight crew experienced windshear during two approaches to Runways 15R and 33L at BWI. The second encounter was severe and the crew elected to divert to their alternate. Flap over speeds occurred during the second go around.

Narrative: I arrived at the aircraft first and started my standard routine. The Captain arrived shortly after and told me that he had talked to Dispatch and decided on changing the alternate to PIT. I told him that I thought that was a real good idea and that I agreed with him completely. Release 2 reflected the new alternate and fuel burn. The climbout and cruise on our scheduled route of flight was uneventful. While enroute to BWI we pulled up the BWI ATIS reports frequently to keep abreast of any changing weather conditions or runway changes. I pulled up a report for BWI and showed it to the Captain. It showed light rain with a gust front (GG) to the west of the airport. The Captain remarked that it was fast moving at 60 KTS. I pulled up the landing weight data for BWI Runway 15R to see if there were any field conditions that we needed to know about. There was none listed. I reviewed the NOTAMs and mentioned that there was nothing that concerned us. The Captain briefed the approach; turn-off; go-around procedures; tuned and set up the NAVAIDs and we set our airspeed bugs for a flaps 25 approach and landing. The winds at BWI were something like 180 degrees; 8 KTS gusting to 17. Our Ref speed was approximately 126 KTS plus a 14 KT addition = 140 KTS. Windshear advisories were listed on the BWI ATIS but that was to be expected with these gusty surface winds.About 100-150 miles from BWI I turned on the seatbelt sign and seated the passengers. We were now at a lower altitude; maybe 15;000 FT. The cloud tops from the weather was still below us; rough but not too threatening. We both had our weather radar switches turned on; mostly green with isolated yellow areas. No red at all. I made a PA directing the Flight Attendants to 'prepare for landing and remain seated' before we entered the cloud tops. Turbulence was mostly light chop and we both thought that maybe we seated the Flight Attendants way too early. Engine heat was turned on. At some point I pulled up another report for BWI. It showed the gust front still west of the airport but slightly closer. While listening to ATC we heard no PIREPs from any other aircraft or adverse advisories from Approach Control. So far it sounded like everyone was getting in to BWI with nothing more than a slightly bumpy ride. Closer in to BWI; Approach Control began to vector us for the ILS 15R approach and descended us to around 4;000 to 5;000 FT. ATC vectored us through the ILS centerline at almost a 90 degree angle; something like a 080 degree heading. Eventually ATC did direct an almost 180 degree turn to the right to intercept the ILS 15R and track the LOC inbound. We make the turn with the autopilot still on. I think ATC gave us a few minor vectors to shallow out the intercept angle. We could see on TCAS that there were a couple aircraft on final ahead of us but still no adverse weather reports at all. Only light chop. The Captain and I were using two different scales on the weather radar; his was closer in; and mine was the next scale out so that we could cross check what each was seeing. Intercepted the LOC easily. The Captain had already dialed the speed back to 180 KTS prior to the outer marker so the flaps had already been extended to 15 or 20. The Captain called for the gear down and set the target speed of 140. I did and completed the Final Descent Checklist. We were cleared for the approach; armed it and captured the glide slope. I set touchdown zone elevation and switched to Tower. Flaps were extended to 25.I reported the outer marker to Tower and I think they gave us landing clearance. The Tower did make a remark that the winds were shifting at the airport. We were actually quite stabilized at this point with a little more than light chop and light to moderate rain. The weather radar still reflected mostly green with areas of yellow. There were some small patches of magenta turbulence dots on the weather radar ahead of us but we never saw any indications that would lead us to think that severe windshear lie just ahead. No aural or visual warnings from the PWS (Proximity Warning System); nothing from Approach Control prior to their hand off to the Tower or from the Tower itself. What started slowly became an instant flash. First; the auto throttles began to advance and slow more than usual. Then; the airspeed began to accelerate and decrease about plus or minus 20 KTS. Having seen this scenario in the simulator we both knew what was beginning to happen. The Captain made a quick decision at this point and remarked 'that's it I'm out of here; going around; flaps 20; positive climb; gear up; spin the altitude up.' I quickly complied. The Captain clicked the autopilot off and hand flew the missed approach-soon to be-windshear recovery. I told Tower that we were missed approach. I don't remember if I gave them the reason why; I was extremely focused on doing more important things at the moment. They instructed us to fly runway heading; climb and maintain 3;000 FT (4;000 FT).The windshear conditions persisted all the way up to our level off altitude and we began to fly out of it. During this first windshear event I would say that the airspeed fluctuations were about plus or minus 20-25 KTS. During the second event that occurred during our approach to Runway 33L the airspeed variations were much more extreme. Once level; we cleaned the flaps up to 5; then 1; then up. Speed set to around 210 KTS. Tower said that they were now changing the airport around to Runway 33L and would we like to do that? We said yes. I made a very quick PA informing the passengers of what just happened and that they were changing the airport around and that we were going to give it another try. The Captain put the autopilot back on when things settled down. I told the Captain to give me a minute to install the approach and extend it. He handled the radio calls; pulled up the ILS 33L approach plates and set the new ILS course. The vector around to Runway 33L happened quickly. Once I finally finished installing and extended the runway centerline we were already in a base turn getting ready to intercept final. I quickly did an Approach checklist. The Captain called for extended flap settings as he slowed the aircraft down. We were told to intercept final; cleared for the ILS 33L approach. Again; the Captain had the gear down with flaps set at 25 and very close to target speed as we crossed the outer marker (GRAFE at 1;500 FT MSL). Weather radar still showed about 60 percent green; 40 percent various yellow areas. None of the yellow areas appeared in a line; mostly patchy locations. No magenta turbulence areas at all this time. I think I had already switched over to Tower and checked in with them when the second event occurred. I'm not sure but we may have been the first aircraft to get vectored around for the ILS 33L approach and ATC didn't have any information that they could advise us of yet. (The Captain said in our debrief that one aircraft was indeed ahead of us).The very first thing I noticed was how rapidly the outside weather color went from a light to medium gray to almost black. Then in an instant; with no warning whatsoever; we were in a full microburst event. Things happened very quickly and it is hard to piece things together in the exact order that they occurred. Again; at the very first indication of unusual autothrottle movement and changing airspeed the Captain quickly initiated a go-around. I set the flaps to 20; raised the gear; and spun the altitude up. I know the airspeed accelerated to nearly 240 KTS; and then dropped off to around 100; then back towards 240. I looked over at the Captain and he was both pulling and pushing the yoke with major force trying to keep things under control. I reached down with my left hand and grabbed the autothrottles to try to stabilize their extreme movements while at the same time informing Tower of our go-around. This time I know I did make the remark 'due to extreme windshear' to Tower. I was well aware that we were over speeding the flaps during this whole event but things happened so quickly with myself working the autothrottles; informing Tower; watching the airspeed fly through the roof one minute and then wondering if the airplane was going to stall the next that I couldn't process what to do (if anything) with the flaps quick enough. Again; no PWS advisories or warnings at all. In hindsight we think that we were just one or two hundred feet above the 1;200 FT AGL altitude that the PWS provides the verbal and visual indications. We climbed up to our assigned altitude of 3;000 or 4;000 FT MSL. It was everything the Captain could do to try to keep the airplane anywhere close to our assigned altitude. I informed Tower that we were just trying to hold altitude the best we could - plus or minus 500 FT. I also told the Tower that we were plus or minus FIFTY KTS. I wanted to make sure the Tower knew the severity of this weather condition to prevent vectoring anybody in just behind us. I took the liberty of setting a speed in the 'speed window' of the MCP that seemed best for all these conditions once we were somewhere near our assigned altitude. Once things began to settle down again the Captain called for flaps 5; then 1; then up. We switched over to Approach Control and I advised them that we were going to proceed to our alternate. ATC gave us continued climbs and vectors onto an airway. During the climbout I sent Dispatch a message informing them of our divert. Dispatch sent an ACARS message suggesting that we go to IAD. The Captain said 'NO we're going to PIT' which I completely agreed with. I know I thought to myself 'I sure don't want to even THINK of having to deal with another windshear issue again' at nearby IAD. I sent in two maintenance messages. One for the flap overspeeds; the second for not receiving any PWS windshear alerts or warnings even thought we were in a complete windshear and then microburst condition. Not even a windshear icon was displayed at any time. The remainder of the flight was uneventful.

Data retrieved from NASA's ASRS site as of April 2012 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.