Air carrier heavy transport made a takeoff from phl in WX reported below airport minimums.

Attributes
ACN	158136
Time
Date	199009
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : phl
State Reference	PA
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Heavy Transport, Low Wing, 4 Turbojet Eng
Flight Phase	climbout : takeoff
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 6000 flight time type : 2200
ASRS Report	158136
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : commercial pilot : atp pilot : instrument
Experience	flight time last 90 days : 75 flight time total : 14000 flight time type : 1000
ASRS Report	158375
Events
Anomaly	non adherence : published procedure non adherence : far
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted none taken : detected after the fact
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

After waiting for hours for takeoff with the tower reported visibility of 1/16-1/8 mi, the visibility improved to 1/4-/12 mi with an RVR of 800-1200'. A check of the commercial plate 10-9A for phl indicated that the visibility needed on runway 27R was RVR 16 or 1/4. Since I was unsure of the exact meaning of 'or' in this instance, I had the first officer check the regulations. He could find no clarification there so I checked a training document which I had with me, which also did not offer any clarification. After some discussion we took RVR 16 or 1/4 to mean either RVR 1600' or 1/4 mi visibility and proceeded to make the takeoff believing that we were legal to do so. En route we discussed this further and decided that the charts were unclr on this issue. I believe the chart should be change as follows: 1) if the 'or' in RVR 16 or 1/4 means either RVR 16 or visibility 1/4 mi, the chart should reflect this. 2) if the 'or' means the most restrictive value, the chart should say, 'the most restrictive of RVR 16 or visibility 1/4 mi.'

Original NASA ASRS Text

Title: ACR HVT MADE A TKOF FROM PHL IN WX REPORTED BELOW ARPT MINIMUMS.

Narrative: AFTER WAITING FOR HRS FOR TKOF WITH THE TWR RPTED VISIBILITY OF 1/16-1/8 MI, THE VISIBILITY IMPROVED TO 1/4-/12 MI WITH AN RVR OF 800-1200'. A CHK OF THE COMMERCIAL PLATE 10-9A FOR PHL INDICATED THAT THE VISIBILITY NEEDED ON RWY 27R WAS RVR 16 OR 1/4. SINCE I WAS UNSURE OF THE EXACT MEANING OF 'OR' IN THIS INSTANCE, I HAD THE F/O CHK THE REGS. HE COULD FIND NO CLARIFICATION THERE SO I CHKED A TRNING DOCUMENT WHICH I HAD WITH ME, WHICH ALSO DID NOT OFFER ANY CLARIFICATION. AFTER SOME DISCUSSION WE TOOK RVR 16 OR 1/4 TO MEAN EITHER RVR 1600' OR 1/4 MI VISIBILITY AND PROCEEDED TO MAKE THE TKOF BELIEVING THAT WE WERE LEGAL TO DO SO. ENRTE WE DISCUSSED THIS FURTHER AND DECIDED THAT THE CHARTS WERE UNCLR ON THIS ISSUE. I BELIEVE THE CHART SHOULD BE CHANGE AS FOLLOWS: 1) IF THE 'OR' IN RVR 16 OR 1/4 MEANS EITHER RVR 16 OR VISIBILITY 1/4 MI, THE CHART SHOULD REFLECT THIS. 2) IF THE 'OR' MEANS THE MOST RESTRICTIVE VALUE, THE CHART SHOULD SAY, 'THE MOST RESTRICTIVE OF RVR 16 OR VISIBILITY 1/4 MI.'

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.