Narrative:

Just as we were talking about and looking for the islands, the master caution alerted us to an 'anti-ice' problem. Captain noticed caution first (perhaps since the anti-ice annunciator is on the right six-pack). Captain cancelled the flasher and determined the left side (#2, sliding window) window heat had failed. Crew deselected the window heat switch for the affected window and consulted the checklist. Visual inspection confirmed a small burned and blistered area in the outer ply. Having seen this condition on other aircraft, I was prepared for the cracking of the outer ply and possible delamination from the inner window. Within about 1 min, there was a noise like a single clap of hands and the outer ply cracked, obscuring about 10-20% of the viewing area. I pressed my finger against the window in order to observe the thickness between the inner window surface and the crack. It was obvious the cracked window was limited to the outer ply. I was comfortable with my assessment and understanding of the situation. In retrospect, it may have appeared I was being casual about the problem, but I knew the integrity of the airframe was not in jeopardy and there was not much we could do to overcome or correct the problem. Conversely, captain had witnessed the cracking of the window and donned his oxygen mask. Using hand motions he indicated that I should turn towards ZZZZ and descend. I thought such action was premature (given the low severity of the problem) and improper (given the fact that there are specific emergency procedures in the nat airspace). Somewhat reluctantly, I donned my oxygen mask, tested the intercom feature and told captain that the failure was limited to the outer ply. He verbally reiterated and gestured the order to turn. The rush to judgement and the fact that captain had not established crew communications via the intercom bothered me. I felt he was overly dramatic and hasty with his unilateral determination of the gravity of the situation. Captain declared an emergency with ZZZZ center. I started a turn toward ZZZZ and a slow descent (1000 FPM). Hoping to add some patience and rational discussion to the situation, I directed captain to the unannunciated procedures section of the non-normal checklist. He had a hard time finding the proper procedure, but eventually went through the procedural steps as if he had a complete (inner and outer ply) crack. Among other things, he raised the cabin altitude to 10000 ft. Captain took a moment to brief the cabin crew of our intentions and how to advise the passenger. It was his intention to make a precautionary landing in ZZZZ. From there we would consider continuation of the flight to our destination. This was the first confirmation I had to his plan. I thought the decision to land was being made before all considerations had been accounted, if not overly conservative. During the descent captain called our operations office to make them aware of our deviation. Captain and I discussed the situation, including the fact that only the outer ply had failed and our present weight was well above our maximum landing weight. Captain advised ZZZZ tower that we no longer had an emergency (explained the 'cockpit window failure') and would advise when we were ready for landing. He then went to the cabin to give a briefing and assurance to the passenger. We made the ILS approach and landed without further incident. As soon as I opened the window and felt the cracks in the outer ply, I knew we would not be leaving soon. The MEL confirmed that a cracked outer ply could not be MEL'ed, but had to be replaced. Landing short of our destination was not required by the situation we encountered. However, in the end the decision to land in ZZZZ cannot be faulted because it was the most conservative opinion on the flight deck. The events and subsequent actions frustrated me because I felt the decision was made prematurely and without all considerations. If there had been more complete CRM I would have been more supportive of the ultimate decision. Captain and I discussed the events and process later. He understood the need to consider more options. He should have also conducted an open discussion with the entire crew.

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Original NASA ASRS Text

Title: A B737-700 IN CRUISE AT FL370 DECLARED AN EMER AND DIVERTED DUE TO THE R SLIDING WINDOW OUTER PANE CRACKING.

Narrative: JUST AS WE WERE TALKING ABOUT AND LOOKING FOR THE ISLANDS, THE MASTER CAUTION ALERTED US TO AN 'ANTI-ICE' PROB. CAPT NOTICED CAUTION FIRST (PERHAPS SINCE THE ANTI-ICE ANNUNCIATOR IS ON THE R SIX-PACK). CAPT CANCELLED THE FLASHER AND DETERMINED THE L SIDE (#2, SLIDING WINDOW) WINDOW HEAT HAD FAILED. CREW DESELECTED THE WINDOW HEAT SWITCH FOR THE AFFECTED WINDOW AND CONSULTED THE CHKLIST. VISUAL INSPECTION CONFIRMED A SMALL BURNED AND BLISTERED AREA IN THE OUTER PLY. HAVING SEEN THIS CONDITION ON OTHER ACFT, I WAS PREPARED FOR THE CRACKING OF THE OUTER PLY AND POSSIBLE DELAMINATION FROM THE INNER WINDOW. WITHIN ABOUT 1 MIN, THERE WAS A NOISE LIKE A SINGLE CLAP OF HANDS AND THE OUTER PLY CRACKED, OBSCURING ABOUT 10-20% OF THE VIEWING AREA. I PRESSED MY FINGER AGAINST THE WINDOW IN ORDER TO OBSERVE THE THICKNESS BTWN THE INNER WINDOW SURFACE AND THE CRACK. IT WAS OBVIOUS THE CRACKED WINDOW WAS LIMITED TO THE OUTER PLY. I WAS COMFORTABLE WITH MY ASSESSMENT AND UNDERSTANDING OF THE SIT. IN RETROSPECT, IT MAY HAVE APPEARED I WAS BEING CASUAL ABOUT THE PROB, BUT I KNEW THE INTEGRITY OF THE AIRFRAME WAS NOT IN JEOPARDY AND THERE WAS NOT MUCH WE COULD DO TO OVERCOME OR CORRECT THE PROB. CONVERSELY, CAPT HAD WITNESSED THE CRACKING OF THE WINDOW AND DONNED HIS OXYGEN MASK. USING HAND MOTIONS HE INDICATED THAT I SHOULD TURN TOWARDS ZZZZ AND DSND. I THOUGHT SUCH ACTION WAS PREMATURE (GIVEN THE LOW SEVERITY OF THE PROB) AND IMPROPER (GIVEN THE FACT THAT THERE ARE SPECIFIC EMER PROCS IN THE NAT AIRSPACE). SOMEWHAT RELUCTANTLY, I DONNED MY OXYGEN MASK, TESTED THE INTERCOM FEATURE AND TOLD CAPT THAT THE FAILURE WAS LIMITED TO THE OUTER PLY. HE VERBALLY REITERATED AND GESTURED THE ORDER TO TURN. THE RUSH TO JUDGEMENT AND THE FACT THAT CAPT HAD NOT ESTABLISHED CREW COMS VIA THE INTERCOM BOTHERED ME. I FELT HE WAS OVERLY DRAMATIC AND HASTY WITH HIS UNILATERAL DETERMINATION OF THE GRAVITY OF THE SIT. CAPT DECLARED AN EMER WITH ZZZZ CTR. I STARTED A TURN TOWARD ZZZZ AND A SLOW DSCNT (1000 FPM). HOPING TO ADD SOME PATIENCE AND RATIONAL DISCUSSION TO THE SIT, I DIRECTED CAPT TO THE UNANNUNCIATED PROCS SECTION OF THE NON-NORMAL CHKLIST. HE HAD A HARD TIME FINDING THE PROPER PROC, BUT EVENTUALLY WENT THROUGH THE PROCEDURAL STEPS AS IF HE HAD A COMPLETE (INNER AND OUTER PLY) CRACK. AMONG OTHER THINGS, HE RAISED THE CABIN ALT TO 10000 FT. CAPT TOOK A MOMENT TO BRIEF THE CABIN CREW OF OUR INTENTIONS AND HOW TO ADVISE THE PAX. IT WAS HIS INTENTION TO MAKE A PRECAUTIONARY LNDG IN ZZZZ. FROM THERE WE WOULD CONSIDER CONTINUATION OF THE FLT TO OUR DEST. THIS WAS THE FIRST CONFIRMATION I HAD TO HIS PLAN. I THOUGHT THE DECISION TO LAND WAS BEING MADE BEFORE ALL CONSIDERATIONS HAD BEEN ACCOUNTED, IF NOT OVERLY CONSERVATIVE. DURING THE DSCNT CAPT CALLED OUR OPS OFFICE TO MAKE THEM AWARE OF OUR DEV. CAPT AND I DISCUSSED THE SIT, INCLUDING THE FACT THAT ONLY THE OUTER PLY HAD FAILED AND OUR PRESENT WT WAS WELL ABOVE OUR MAX LNDG WT. CAPT ADVISED ZZZZ TWR THAT WE NO LONGER HAD AN EMER (EXPLAINED THE 'COCKPIT WINDOW FAILURE') AND WOULD ADVISE WHEN WE WERE READY FOR LNDG. HE THEN WENT TO THE CABIN TO GIVE A BRIEFING AND ASSURANCE TO THE PAX. WE MADE THE ILS APCH AND LANDED WITHOUT FURTHER INCIDENT. AS SOON AS I OPENED THE WINDOW AND FELT THE CRACKS IN THE OUTER PLY, I KNEW WE WOULD NOT BE LEAVING SOON. THE MEL CONFIRMED THAT A CRACKED OUTER PLY COULD NOT BE MEL'ED, BUT HAD TO BE REPLACED. LNDG SHORT OF OUR DEST WAS NOT REQUIRED BY THE SIT WE ENCOUNTERED. HOWEVER, IN THE END THE DECISION TO LAND IN ZZZZ CANNOT BE FAULTED BECAUSE IT WAS THE MOST CONSERVATIVE OPINION ON THE FLT DECK. THE EVENTS AND SUBSEQUENT ACTIONS FRUSTRATED ME BECAUSE I FELT THE DECISION WAS MADE PREMATURELY AND WITHOUT ALL CONSIDERATIONS. IF THERE HAD BEEN MORE COMPLETE CRM I WOULD HAVE BEEN MORE SUPPORTIVE OF THE ULTIMATE DECISION. CAPT AND I DISCUSSED THE EVENTS AND PROCESS LATER. HE UNDERSTOOD THE NEED TO CONSIDER MORE OPTIONS. HE SHOULD HAVE ALSO CONDUCTED AN OPEN DISCUSSION WITH THE ENTIRE CREW.

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.