Narrative:

I was the PF. At about FL280 in a descent to cross lozit at 11000 ft the captain's forward windshield began arcing near the upper left corner for about 3 seconds followed immediately by the entire outer layer completely cracking throughout the entire area of the windshield. We immediately donned our oxygen masks and notified ATC of the problem. I slowed the aircraft to 250 KIAS and ATC gave us a vector left of course and then right of course for the descent. The captain then started the irregular procedure for a damaged/cracked windshield. As per the checklist we depressurized the aircraft passing 9000 ft. We did not declare an emergency; but asked ATC for a longer final; so that we could descend slower due to being depressurized. The captain informed the purser and passenger of the problem before we depressurized. We flew an uneventful approach to runway 28R to sfo. The aircraft flew normally during the entire evolution. Supplemental information from acn 762900: my comments regarding the 'window (cockpit) damage' irregular procedure. One: the note specifying 'L1; L2; R1; R2 inner pane' is less obvious than I feel it should be. And; whether or not reflected in the order of steps outlined in the procedure; prudence would indicate donning oxygen as soon as cracks are forming all over the glass. If the note were to apply; the need for precautionary oxygen has already arisen. In my case and once the mask was on; I didn't see the note. What I saw was 'cracked/shattered L1;' and continued with that list. Consider placing 'oxygen masks on' at the beginning of the procedure and then making an obvious note providing for their removal if only an outer pane is damaged. Additionally; by organizing the checklist as worst-case first followed by an obvious provision for 'outer pane only;' the need to see subtle notes in order to determine a possible diversion is removed. Reading notes with oxygen donned is difficult. Two: under the subtitle 'at 9000 ft' step outflow valve switch open is an instruction to 'hold outflow valve switch to open until valve indicates fully open.' when operating this switch in manual AC; as instructed; this switch must be toggled until the valve is open; not held. First officer was having some difficulty getting the valve fully open and then realized that if the outflow valve switch is held open; the flight/ground switch has to be toggled to ground in order for the valve to move; or the checklist has to be ignored and the outflow valve switch in fact; toggled.

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Original NASA ASRS Text

Title: B737-300 WINDSHIELD BEGAN ARCING AND SUBSEQUENTLY THE OUTER PANE SHATTERED.

Narrative: I WAS THE PF. AT ABOUT FL280 IN A DSCNT TO CROSS LOZIT AT 11000 FT THE CAPT'S FORWARD WINDSHIELD BEGAN ARCING NEAR THE UPPER L CORNER FOR ABOUT 3 SECONDS FOLLOWED IMMEDIATELY BY THE ENTIRE OUTER LAYER COMPLETELY CRACKING THROUGHOUT THE ENTIRE AREA OF THE WINDSHIELD. WE IMMEDIATELY DONNED OUR OXYGEN MASKS AND NOTIFIED ATC OF THE PROB. I SLOWED THE ACFT TO 250 KIAS AND ATC GAVE US A VECTOR L OF COURSE AND THEN R OF COURSE FOR THE DSCNT. THE CAPT THEN STARTED THE IRREGULAR PROC FOR A DAMAGED/CRACKED WINDSHIELD. AS PER THE CHKLIST WE DEPRESSURIZED THE ACFT PASSING 9000 FT. WE DID NOT DECLARE AN EMER; BUT ASKED ATC FOR A LONGER FINAL; SO THAT WE COULD DSND SLOWER DUE TO BEING DEPRESSURIZED. THE CAPT INFORMED THE PURSER AND PAX OF THE PROB BEFORE WE DEPRESSURIZED. WE FLEW AN UNEVENTFUL APCH TO RWY 28R TO SFO. THE ACFT FLEW NORMALLY DURING THE ENTIRE EVOLUTION. SUPPLEMENTAL INFO FROM ACN 762900: MY COMMENTS REGARDING THE 'WINDOW (COCKPIT) DAMAGE' IRREGULAR PROC. ONE: THE NOTE SPECIFYING 'L1; L2; R1; R2 INNER PANE' IS LESS OBVIOUS THAN I FEEL IT SHOULD BE. AND; WHETHER OR NOT REFLECTED IN THE ORDER OF STEPS OUTLINED IN THE PROC; PRUDENCE WOULD INDICATE DONNING OXYGEN AS SOON AS CRACKS ARE FORMING ALL OVER THE GLASS. IF THE NOTE WERE TO APPLY; THE NEED FOR PRECAUTIONARY OXYGEN HAS ALREADY ARISEN. IN MY CASE AND ONCE THE MASK WAS ON; I DIDN'T SEE THE NOTE. WHAT I SAW WAS 'CRACKED/SHATTERED L1;' AND CONTINUED WITH THAT LIST. CONSIDER PLACING 'OXYGEN MASKS ON' AT THE BEGINNING OF THE PROC AND THEN MAKING AN OBVIOUS NOTE PROVIDING FOR THEIR REMOVAL IF ONLY AN OUTER PANE IS DAMAGED. ADDITIONALLY; BY ORGANIZING THE CHKLIST AS WORST-CASE FIRST FOLLOWED BY AN OBVIOUS PROVISION FOR 'OUTER PANE ONLY;' THE NEED TO SEE SUBTLE NOTES IN ORDER TO DETERMINE A POSSIBLE DIVERSION IS REMOVED. READING NOTES WITH OXYGEN DONNED IS DIFFICULT. TWO: UNDER THE SUBTITLE 'AT 9000 FT' STEP OUTFLOW VALVE SWITCH OPEN IS AN INSTRUCTION TO 'HOLD OUTFLOW VALVE SWITCH TO OPEN UNTIL VALVE INDICATES FULLY OPEN.' WHEN OPERATING THIS SWITCH IN MANUAL AC; AS INSTRUCTED; THIS SWITCH MUST BE TOGGLED UNTIL THE VALVE IS OPEN; NOT HELD. FO WAS HAVING SOME DIFFICULTY GETTING THE VALVE FULLY OPEN AND THEN REALIZED THAT IF THE OUTFLOW VALVE SWITCH IS HELD OPEN; THE FLT/GND SWITCH HAS TO BE TOGGLED TO GND IN ORDER FOR THE VALVE TO MOVE; OR THE CHKLIST HAS TO BE IGNORED AND THE OUTFLOW VALVE SWITCH IN FACT; TOGGLED.

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.