Narrative:

Before taxi at phl the question of a takeoff alternate came up (indefinite 100 obscured) so I pulled the plate out and read the mins for 9R (6,6,6, RVR) for takeoff and landing (7,7,7, CAT IIIA). Since WX was less than CAT I we requested and received a takeoff alternate. We taxied out and joined the line for 9L. Aircraft continued to land on 9R and takeoff on 9L as RVR varied from 1600 to 2400 ft. Tower had us position and hold and as we lined up he stated that tower visibility was 1/8 mi and could we accept that. (I believe this was the first mention of tower visibility although RVR for 9R had been mentioned many times). We could clearly see a mi and clearly see 9R (which is closer than the tower) so I said þrogerþ and we rolled for takeoff on 9L. As we did so, the tower began to poll everybody in line behind us. Up to our frequency change, everybody said yes and we stated runway visibility was a mi or more. At about 1000 ft, the first officer stated that þheþd screwed usþ. After rereading the back of the approach plate, I noted that 9R takeoff mins were on a lower line and said. Adequate visual reference and 1/2 mi in the lower box. We looked up adequate visual reference and were unable to decide if weþd been legal or not. Iþd incorrectly had the 9R mins in my head when the tower stated þ1/8 mi visibilityþ. Of course, any pilot knows that tower visibility does not in reality always reflect runway visibility (especially when the tower is distant and 143 ft tall with a reported ceiling of 100 ft). I guess we were supposed to say (as we were in position) þexcuse me, could you wait a few mins while we look it upþ which runs counter to pilot instincts when one is in position with a long line of aircraft waiting behind. I have known tower to repos one at the end of a line when they were not immediately ready for takeoff in position. Our training and normal procedures require us not to take position unless we are ready for takeoff. If the tower is using tower visibility as his criteria for a runway he should have stated (before having somebody position) that runway visibility is 1/8 mi or something to that effect. Supplemental information from acn 200239: we were proceeding with our takeoff based on adequate visibility reference which as stated by the þunidentified acftþ was at least 1 mi. We accepted the takeoff clearance because we could see the þcþ concourse, which is abeam the charlie (C) taxiway, which is approximately at the half way point of 9L, which is 9500 ft in length, which makes the visibility at least 1/2 mile but probably closer to 3/4 to even 1 mi. We felt that this met the criteria applicable to the adequate visibility reference 1/4 mi for takeoff.

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Original NASA ASRS Text

Title: ACR MLG FLC PERFORM TKOF ON RWY WITH LESS THAN REQUIRED TWR VISIBILITY.

Narrative: BEFORE TAXI AT PHL THE QUESTION OF A TKOF ALTERNATE CAME UP (INDEFINITE 100 OBSCURED) SO I PULLED THE PLATE OUT AND READ THE MINS FOR 9R (6,6,6, RVR) FOR TKOF AND LNDG (7,7,7, CAT IIIA). SINCE WX WAS LESS THAN CAT I WE REQUESTED AND RECEIVED A TKOF ALTERNATE. WE TAXIED OUT AND JOINED THE LINE FOR 9L. ACFT CONTINUED TO LAND ON 9R AND TKOF ON 9L AS RVR VARIED FROM 1600 TO 2400 FT. TWR HAD US POS AND HOLD AND AS WE LINED UP HE STATED THAT TWR VISIBILITY WAS 1/8 MI AND COULD WE ACCEPT THAT. (I BELIEVE THIS WAS THE FIRST MENTION OF TWR VISIBILITY ALTHOUGH RVR FOR 9R HAD BEEN MENTIONED MANY TIMES). WE COULD CLRLY SEE A MI AND CLRLY SEE 9R (WHICH IS CLOSER THAN THE TWR) SO I SAID þROGERþ AND WE ROLLED FOR TKOF ON 9L. AS WE DID SO, THE TWR BEGAN TO POLL EVERYBODY IN LINE BEHIND US. UP TO OUR FREQ CHANGE, EVERYBODY SAID YES AND WE STATED RWY VISIBILITY WAS A MI OR MORE. AT ABOUT 1000 FT, THE FO STATED THAT þHEþD SCREWED USþ. AFTER REREADING THE BACK OF THE APCH PLATE, I NOTED THAT 9R TKOF MINS WERE ON A LOWER LINE AND SAID. ADEQUATE VISUAL REF AND 1/2 MI IN THE LOWER BOX. WE LOOKED UP ADEQUATE VISUAL REF AND WERE UNABLE TO DECIDE IF WEþD BEEN LEGAL OR NOT. IþD INCORRECTLY HAD THE 9R MINS IN MY HEAD WHEN THE TWR STATED þ1/8 MI VISIBILITYþ. OF COURSE, ANY PLT KNOWS THAT TWR VISIBILITY DOES NOT IN REALITY ALWAYS REFLECT RWY VISIBILITY (ESPECIALLY WHEN THE TWR IS DISTANT AND 143 FT TALL WITH A RPTED CEILING OF 100 FT). I GUESS WE WERE SUPPOSED TO SAY (AS WE WERE IN POS) þEXCUSE ME, COULD YOU WAIT A FEW MINS WHILE WE LOOK IT UPþ WHICH RUNS COUNTER TO PLT INSTINCTS WHEN ONE IS IN POS WITH A LONG LINE OF ACFT WAITING BEHIND. I HAVE KNOWN TWR TO REPOS ONE AT THE END OF A LINE WHEN THEY WERE NOT IMMEDIATELY READY FOR TKOF IN POS. OUR TRAINING AND NORMAL PROCS REQUIRE US NOT TO TAKE POS UNLESS WE ARE READY FOR TKOF. IF THE TWR IS USING TWR VISIBILITY AS HIS CRITERIA FOR A RWY HE SHOULD HAVE STATED (BEFORE HAVING SOMEBODY POS) THAT RWY VISIBILITY IS 1/8 MI OR SOMETHING TO THAT EFFECT. SUPPLEMENTAL INFO FROM ACN 200239: WE WERE PROCEEDING WITH OUR TKOF BASED ON ADEQUATE VISIBILITY REF WHICH AS STATED BY THE þUNIDENTIFIED ACFTþ WAS AT LEAST 1 MI. WE ACCEPTED THE TKOF CLRNC BECAUSE WE COULD SEE THE þCþ CONCOURSE, WHICH IS ABEAM THE CHARLIE (C) TAXIWAY, WHICH IS APPROX AT THE HALF WAY POINT OF 9L, WHICH IS 9500 FT IN LENGTH, WHICH MAKES THE VISIBILITY AT LEAST 1/2 MILE BUT PROBABLY CLOSER TO 3/4 TO EVEN 1 MI. WE FELT THAT THIS MET THE CRITERIA APPLICABLE TO THE ADEQUATE VISIBILITY REF 1/4 MI FOR TKOF.

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.