Narrative:

At approximately XA30, while ferrying a saab aircraft from hpn to bos (as the PF), we were beginning the ILS approach to runway 33L bos under visual conditions. There was a line of thunderstorms approaching from the opposite side of the airport from the northwest. We had our radar on and set to 25 NM. The line of storms was still west of the airport by 2-3 mi as we began the approach. The only significant build-ups were clearly visible above the preceding overcast that apparently was the WX front's leading edge. There was no visible indication at any time of any imminent hazard. We did, however, heard and heed the report of the aircraft on the approach in front of us, a brasilia, that reported airspeed variations of 5 KIAS. We fully expected the turbulence associated with a frontal crossing. ATC had previously slowed us to 170 KIAS and cleared us for the approach as we descended through 7000 ft MSL and 20 DME. I called for flaps 15 degrees. At about 12 DME, we started to pass about 1000 ft below the overcast layer. I stated to the first officer that this would be the place where the bumps would begin. Just after passing under the boundary of the overcast, the light to moderate turbulence indeed did begin. Then, suddenly without any warning, we were struck by a severe windshear downdraft pointing us nose down. Our airspeed instantly jumped to 200 KIAS. I reached over and selected flaps up myself because I couldn't shout out the command fast enough. The total duration of the event was 10-20 seconds. We saw the airspeed maximum out at 248 KTS (no vmo horn) and the vertical speed went to -4000 FPM. The GPWS was sounding off repeatedly even after we managed to do the windshear escape maneuver to level off at about 2500 ft MSL. The GPWS finally stopped as we approached the FAF. We re-established ourselves on the ILS by about 2 mi outside the FAF. Runway 33L was in sight the entire time so we continued the approach to land without any further incident or abnormality. I wrote up the exceeding of the flaps 15 degree speed in the aircraft maintenance log and personally told maintenance that they should look the aircraft over for any signs of overstress. Supplemental information from acn 554678: I ws the PNF, jul/xx/02. Ferry flight from hpn to bos. Line of WX on radar just northwest of airport. At 20 DME, established on localizer runway 33L, ATC cleared us for the approach. Visual contact with runway the entire approach. ATIS information was current with winds from 250 degrees at 21 KTS gusting to 29 KTS, reports of 5 KTS at 3500 ft from ATC. At 7000 ft we intercepted the GS. ATC instructed us to maintain 170 KTS till hullz (FAF). At approximately 17 DME off ilip, captain called for flaps 15 degrees. At 12 DME we encountered windshear that forced the plane's nose toward the ground. Terrain alert sounded, airspeed increased through 200 KTS. Back on approach. Pwred back 2-3 NM from hullz. Re-established for normal landing.

Related reports:

Google
 

Original NASA ASRS Text

Title: SAAB FLC ENCOUNTERS WINDSHEAR ON APCH TO BOS.

Narrative: AT APPROX XA30, WHILE FERRYING A SAAB ACFT FROM HPN TO BOS (AS THE PF), WE WERE BEGINNING THE ILS APCH TO RWY 33L BOS UNDER VISUAL CONDITIONS. THERE WAS A LINE OF TSTMS APCHING FROM THE OPPOSITE SIDE OF THE ARPT FROM THE NW. WE HAD OUR RADAR ON AND SET TO 25 NM. THE LINE OF STORMS WAS STILL W OF THE ARPT BY 2-3 MI AS WE BEGAN THE APCH. THE ONLY SIGNIFICANT BUILD-UPS WERE CLRLY VISIBLE ABOVE THE PRECEDING OVCST THAT APPARENTLY WAS THE WX FRONT'S LEADING EDGE. THERE WAS NO VISIBLE INDICATION AT ANY TIME OF ANY IMMINENT HAZARD. WE DID, HOWEVER, HEARD AND HEED THE RPT OF THE ACFT ON THE APCH IN FRONT OF US, A BRASILIA, THAT RPTED AIRSPD VARIATIONS OF 5 KIAS. WE FULLY EXPECTED THE TURB ASSOCIATED WITH A FRONTAL XING. ATC HAD PREVIOUSLY SLOWED US TO 170 KIAS AND CLRED US FOR THE APCH AS WE DSNDED THROUGH 7000 FT MSL AND 20 DME. I CALLED FOR FLAPS 15 DEGS. AT ABOUT 12 DME, WE STARTED TO PASS ABOUT 1000 FT BELOW THE OVCST LAYER. I STATED TO THE FO THAT THIS WOULD BE THE PLACE WHERE THE BUMPS WOULD BEGIN. JUST AFTER PASSING UNDER THE BOUNDARY OF THE OVCST, THE LIGHT TO MODERATE TURB INDEED DID BEGIN. THEN, SUDDENLY WITHOUT ANY WARNING, WE WERE STRUCK BY A SEVERE WINDSHEAR DOWNDRAFT POINTING US NOSE DOWN. OUR AIRSPD INSTANTLY JUMPED TO 200 KIAS. I REACHED OVER AND SELECTED FLAPS UP MYSELF BECAUSE I COULDN'T SHOUT OUT THE COMMAND FAST ENOUGH. THE TOTAL DURATION OF THE EVENT WAS 10-20 SECONDS. WE SAW THE AIRSPD MAX OUT AT 248 KTS (NO VMO HORN) AND THE VERT SPD WENT TO -4000 FPM. THE GPWS WAS SOUNDING OFF REPEATEDLY EVEN AFTER WE MANAGED TO DO THE WINDSHEAR ESCAPE MANEUVER TO LEVEL OFF AT ABOUT 2500 FT MSL. THE GPWS FINALLY STOPPED AS WE APCHED THE FAF. WE RE-ESTABLISHED OURSELVES ON THE ILS BY ABOUT 2 MI OUTSIDE THE FAF. RWY 33L WAS IN SIGHT THE ENTIRE TIME SO WE CONTINUED THE APCH TO LAND WITHOUT ANY FURTHER INCIDENT OR ABNORMALITY. I WROTE UP THE EXCEEDING OF THE FLAPS 15 DEG SPD IN THE ACFT MAINT LOG AND PERSONALLY TOLD MAINT THAT THEY SHOULD LOOK THE ACFT OVER FOR ANY SIGNS OF OVERSTRESS. SUPPLEMENTAL INFO FROM ACN 554678: I WS THE PNF, JUL/XX/02. FERRY FLT FROM HPN TO BOS. LINE OF WX ON RADAR JUST NW OF ARPT. AT 20 DME, ESTABLISHED ON LOC RWY 33L, ATC CLRED US FOR THE APCH. VISUAL CONTACT WITH RWY THE ENTIRE APCH. ATIS INFO WAS CURRENT WITH WINDS FROM 250 DEGS AT 21 KTS GUSTING TO 29 KTS, RPTS OF 5 KTS AT 3500 FT FROM ATC. AT 7000 FT WE INTERCEPTED THE GS. ATC INSTRUCTED US TO MAINTAIN 170 KTS TILL HULLZ (FAF). AT APPROX 17 DME OFF ILIP, CAPT CALLED FOR FLAPS 15 DEGS. AT 12 DME WE ENCOUNTERED WINDSHEAR THAT FORCED THE PLANE'S NOSE TOWARD THE GND. TERRAIN ALERT SOUNDED, AIRSPD INCREASED THROUGH 200 KTS. BACK ON APCH. PWRED BACK 2-3 NM FROM HULLZ. RE-ESTABLISHED FOR NORMAL LNDG.

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.