Narrative:

Our flight was holding over pvd due to fog at bos. ZBW made a general inquiry of the aircraft in the stack if anyone could take the approach on bos 4R, and gave the current field conditions. We checked our approach plate and determined that we were within limits for the 4R CAT ii approach. We responded that we would like the approach and were vectored out of the hold. We asked ZBW for verification that CAT ii approachs were being conducted to 4R and received an affirmative reply. We were vectored to intercept the 4R localizer. At 6000' bos approach reported the R4 RVR as 1600' and cleared us for the 4R ILS. It is uncertain if the approach controller included CAT ii terminology in his clearance for the approach, however we believed that was the clearance. At approximately 15 mi from T/D at the captain's request, I inquired if there was anyone in front of us. Approach control initially responded yes, then stated no--that the aircraft in front of us had abandoned the approach due to RVR dropping 1000 (1200 required). I replied that we would continue a little further to see if the RVR would come back up to 120. The captain then stated that once you were cleared for the approach you could continue even if the RVR dropped below limits and be intended to continue the approach. On final the tower again reported RVR 1000. At approximately 200' AGL the captain reported the approach lights in sight and continued to a normal T/D and rollout. The crew and aircraft were both CAT ii qualified and the approach was conducted in accordance with company procedures.

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Original NASA ASRS Text

Title: ACR MLG MAY HAVE BEGUN ILS CAT II APCH WHEN ARPT WAS BELOW LNDG MINIMUMS.

Narrative: OUR FLT WAS HOLDING OVER PVD DUE TO FOG AT BOS. ZBW MADE A GENERAL INQUIRY OF THE ACFT IN THE STACK IF ANYONE COULD TAKE THE APCH ON BOS 4R, AND GAVE THE CURRENT FIELD CONDITIONS. WE CHKED OUR APCH PLATE AND DETERMINED THAT WE WERE WITHIN LIMITS FOR THE 4R CAT II APCH. WE RESPONDED THAT WE WOULD LIKE THE APCH AND WERE VECTORED OUT OF THE HOLD. WE ASKED ZBW FOR VERIFICATION THAT CAT II APCHS WERE BEING CONDUCTED TO 4R AND RECEIVED AN AFFIRMATIVE REPLY. WE WERE VECTORED TO INTERCEPT THE 4R LOC. AT 6000' BOS APCH RPTED THE R4 RVR AS 1600' AND CLRED US FOR THE 4R ILS. IT IS UNCERTAIN IF THE APCH CTLR INCLUDED CAT II TERMINOLOGY IN HIS CLRNC FOR THE APCH, HOWEVER WE BELIEVED THAT WAS THE CLRNC. AT APPROX 15 MI FROM T/D AT THE CAPT'S REQUEST, I INQUIRED IF THERE WAS ANYONE IN FRONT OF US. APCH CTL INITIALLY RESPONDED YES, THEN STATED NO--THAT THE ACFT IN FRONT OF US HAD ABANDONED THE APCH DUE TO RVR DROPPING 1000 (1200 REQUIRED). I REPLIED THAT WE WOULD CONTINUE A LITTLE FURTHER TO SEE IF THE RVR WOULD COME BACK UP TO 120. THE CAPT THEN STATED THAT ONCE YOU WERE CLRED FOR THE APCH YOU COULD CONTINUE EVEN IF THE RVR DROPPED BELOW LIMITS AND BE INTENDED TO CONTINUE THE APCH. ON FINAL THE TWR AGAIN RPTED RVR 1000. AT APPROX 200' AGL THE CAPT RPTED THE APCH LIGHTS IN SIGHT AND CONTINUED TO A NORMAL T/D AND ROLLOUT. THE CREW AND ACFT WERE BOTH CAT II QUALIFIED AND THE APCH WAS CONDUCTED IN ACCORDANCE WITH COMPANY PROCS.

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.