Narrative:

This situation occurred when flying the ILS to runway 33L at bos. About 8-9 mi out on final approach, bos approach slowed us from 180 KTS to 170 KTS until hullz intersection. As we approached hullz, approach control switched us over to tower. Immediately after contacting tower they told us to slow to our approach speed, which we were already starting to do. They also notified us that there was traffic holding in the takeoff position. The first officer, who was the PF, recognized there was a chance we might be doing a go around and briefed our go around procedures. At some point around here, I do not remember exactly when, tower cleared the aircraft holding on the runway to takeoff. When we broke out of the WX, we noticed that the aircraft on the runway had delayed his takeoff roll. Around 800-900 ft AGL, tower told us to continue, but gave us no landing clearance. Both the first officer and I recognized that it would be tight and were prepared to go around. We received our landing clearance about 400-500 ft AGL. I elected to accept the landing clearance and continue to landing. It looked very close, but I believed that the tower control had a better angle to judge our spacing. My perspective was somewhat blurred by rain and mist in the air and the wipers doing a marginal job clearing the rain from the windshield. Around 100 ft AGL we went through wake turbulence or jetwash created by the taking off aircraft. It took the first officer's full attention to fly through the disturbed air and he did so very well maintaining a stable approach. We landed safely with a normal rollout and the other aircraft took off normally. I believe that the time we made our touchdown was at the same time the other aircraft got airborne or possibly just before. It was very close for me to see for sure, but it was definitely not comfortable. The spacing between our aircraft and the taking off aircraft was way too tight. I should have had the first officer execute a go around when we saw that the aircraft taking off delayed his takeoff roll. There are a few reasons I chose to continue to landing. First, I trusted the tower's judgement on our spacing. Second, I have learned in my brief experience flying for an air carrier Y that tight spacing is common, so I accepted it as almost normal operations. Other operational thoughts were that I did not want to delay the passenger getting to the gate and burn any extra fuel doing a go around if not necessary. None of these are good reasons to not do a go around! Another factor is that I got sucked into a point where I felt doing a go around would have presented a possible airborne conflict with the same aircraft. Tower told us to continue at a time when we should have done the go around. When we went lower I felt doing a go around would have put us in a situation accelerating straight ahead right behind the takeoff aircraft and both of us being IMC very close together and low to the ground. There was no buffer in this situation if anything went wrong. It was very much a lesson learned for me and reinforced the idea to go around early when it doesn't look right.

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Original NASA ASRS Text

Title: A B737 FLT CREW EXPERIENCE WAKE TURB FROM A CLOSE DEPARTING ACFT WHILE LNDG AT BOS.

Narrative: THIS SIT OCCURRED WHEN FLYING THE ILS TO RWY 33L AT BOS. ABOUT 8-9 MI OUT ON FINAL APCH, BOS APCH SLOWED US FROM 180 KTS TO 170 KTS UNTIL HULLZ INTXN. AS WE APCHED HULLZ, APCH CTL SWITCHED US OVER TO TWR. IMMEDIATELY AFTER CONTACTING TWR THEY TOLD US TO SLOW TO OUR APCH SPD, WHICH WE WERE ALREADY STARTING TO DO. THEY ALSO NOTIFIED US THAT THERE WAS TFC HOLDING IN THE TKOF POS. THE FO, WHO WAS THE PF, RECOGNIZED THERE WAS A CHANCE WE MIGHT BE DOING A GAR AND BRIEFED OUR GAR PROCS. AT SOME POINT AROUND HERE, I DO NOT REMEMBER EXACTLY WHEN, TWR CLRED THE ACFT HOLDING ON THE RWY TO TKOF. WHEN WE BROKE OUT OF THE WX, WE NOTICED THAT THE ACFT ON THE RWY HAD DELAYED HIS TKOF ROLL. AROUND 800-900 FT AGL, TWR TOLD US TO CONTINUE, BUT GAVE US NO LNDG CLRNC. BOTH THE FO AND I RECOGNIZED THAT IT WOULD BE TIGHT AND WERE PREPARED TO GO AROUND. WE RECEIVED OUR LNDG CLRNC ABOUT 400-500 FT AGL. I ELECTED TO ACCEPT THE LNDG CLRNC AND CONTINUE TO LNDG. IT LOOKED VERY CLOSE, BUT I BELIEVED THAT THE TWR CTL HAD A BETTER ANGLE TO JUDGE OUR SPACING. MY PERSPECTIVE WAS SOMEWHAT BLURRED BY RAIN AND MIST IN THE AIR AND THE WIPERS DOING A MARGINAL JOB CLRING THE RAIN FROM THE WINDSHIELD. AROUND 100 FT AGL WE WENT THROUGH WAKE TURB OR JETWASH CREATED BY THE TAKING OFF ACFT. IT TOOK THE FO'S FULL ATTN TO FLY THROUGH THE DISTURBED AIR AND HE DID SO VERY WELL MAINTAINING A STABLE APCH. WE LANDED SAFELY WITH A NORMAL ROLLOUT AND THE OTHER ACFT TOOK OFF NORMALLY. I BELIEVE THAT THE TIME WE MADE OUR TOUCHDOWN WAS AT THE SAME TIME THE OTHER ACFT GOT AIRBORNE OR POSSIBLY JUST BEFORE. IT WAS VERY CLOSE FOR ME TO SEE FOR SURE, BUT IT WAS DEFINITELY NOT COMFORTABLE. THE SPACING BTWN OUR ACFT AND THE TAKING OFF ACFT WAS WAY TOO TIGHT. I SHOULD HAVE HAD THE FO EXECUTE A GAR WHEN WE SAW THAT THE ACFT TAKING OFF DELAYED HIS TKOF ROLL. THERE ARE A FEW REASONS I CHOSE TO CONTINUE TO LNDG. FIRST, I TRUSTED THE TWR'S JUDGEMENT ON OUR SPACING. SECOND, I HAVE LEARNED IN MY BRIEF EXPERIENCE FLYING FOR AN ACR Y THAT TIGHT SPACING IS COMMON, SO I ACCEPTED IT AS ALMOST NORMAL OPS. OTHER OPERATIONAL THOUGHTS WERE THAT I DID NOT WANT TO DELAY THE PAX GETTING TO THE GATE AND BURN ANY EXTRA FUEL DOING A GAR IF NOT NECESSARY. NONE OF THESE ARE GOOD REASONS TO NOT DO A GAR! ANOTHER FACTOR IS THAT I GOT SUCKED INTO A POINT WHERE I FELT DOING A GAR WOULD HAVE PRESENTED A POSSIBLE AIRBORNE CONFLICT WITH THE SAME ACFT. TWR TOLD US TO CONTINUE AT A TIME WHEN WE SHOULD HAVE DONE THE GAR. WHEN WE WENT LOWER I FELT DOING A GAR WOULD HAVE PUT US IN A SIT ACCELERATING STRAIGHT AHEAD RIGHT BEHIND THE TKOF ACFT AND BOTH OF US BEING IMC VERY CLOSE TOGETHER AND LOW TO THE GND. THERE WAS NO BUFFER IN THIS SIT IF ANYTHING WENT WRONG. IT WAS VERY MUCH A LESSON LEARNED FOR ME AND REINFORCED THE IDEA TO GO AROUND EARLY WHEN IT DOESN'T LOOK RIGHT.

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.