B757 crew departs in weather conditions described as -plra in violation of FARS.

Attributes
ACN	731844
Time
Date	200703
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : jfk.airport
State Reference	NY
Altitude	agl single value : 0
Environment
Weather Elements	other
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Flight Phase	ground : parked
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 150 flight time total : 15800 flight time type : 5800
ASRS Report	731844
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	non adherence : far
Independent Detector	other flight crewa
Resolutory Action	none taken : detected after the fact
Supplementary
Problem Areas	Company Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

At the gate at jfk-plra we deiced once and when I checked the flight manual holdover times I noticed we only had 25 mins to get airborne. We were fast approaching that and knew we would not make the holdover time. We elected to deice again with 2 trucks and asked ground how long a delay for takeoff. They said no delay. We taxied out and were airborne well within the 25 min limit performing all winter operations procedures. The takeoff and flight to ZZZ were uneventful. After speaking with the captain several days later we realized -pl mixed with any other precipitation is a no fly situation. I read the restrs but either missed or confused the note after the bold faced ice pellets. 'The preceding flts may not operate' note is confusing in that it states when one of the following 3 types of precipitation is falling at the airport. I think I looked at each of the 3 types as one and did not make the connection of 'pl' mixed with another form of precipitation as 2 separate forms of precipitation. Maybe a rewrite with more specific guidance of prohibited operations would be helpful. In any event I remember commenting to the captain that at the time of our takeoff there appeared to be no precipitation falling at all and we were good to go. I believe the flight was conducted in a completely safe manner.

Original NASA ASRS Text

Title: B757 CREW DEPARTS IN WEATHER CONDITIONS DESCRIBED AS -PLRA IN VIOLATION OF FARS.

Narrative: AT THE GATE AT JFK-PLRA WE DEICED ONCE AND WHEN I CHKED THE FLT MANUAL HOLDOVER TIMES I NOTICED WE ONLY HAD 25 MINS TO GET AIRBORNE. WE WERE FAST APCHING THAT AND KNEW WE WOULD NOT MAKE THE HOLDOVER TIME. WE ELECTED TO DEICE AGAIN WITH 2 TRUCKS AND ASKED GND HOW LONG A DELAY FOR TKOF. THEY SAID NO DELAY. WE TAXIED OUT AND WERE AIRBORNE WELL WITHIN THE 25 MIN LIMIT PERFORMING ALL WINTER OPS PROCS. THE TKOF AND FLT TO ZZZ WERE UNEVENTFUL. AFTER SPEAKING WITH THE CAPT SEVERAL DAYS LATER WE REALIZED -PL MIXED WITH ANY OTHER PRECIP IS A NO FLY SITUATION. I READ THE RESTRS BUT EITHER MISSED OR CONFUSED THE NOTE AFTER THE BOLD FACED ICE PELLETS. 'THE PRECEDING FLTS MAY NOT OPERATE' NOTE IS CONFUSING IN THAT IT STATES WHEN ONE OF THE FOLLOWING 3 TYPES OF PRECIP IS FALLING AT THE ARPT. I THINK I LOOKED AT EACH OF THE 3 TYPES AS ONE AND DID NOT MAKE THE CONNECTION OF 'PL' MIXED WITH ANOTHER FORM OF PRECIP AS 2 SEPARATE FORMS OF PRECIP. MAYBE A REWRITE WITH MORE SPECIFIC GUIDANCE OF PROHIBITED OPS WOULD BE HELPFUL. IN ANY EVENT I REMEMBER COMMENTING TO THE CAPT THAT AT THE TIME OF OUR TKOF THERE APPEARED TO BE NO PRECIP FALLING AT ALL AND WE WERE GOOD TO GO. I BELIEVE THE FLT WAS CONDUCTED IN A COMPLETELY SAFE MANNER.

Data retrieved from NASA's ASRS site as of January 2009 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.