CAPT OF A B727-100 QUESTIONED WHETHER IT WAS LEGAL TO OPERATE THE ACFT WITH THE CAPT'S OUTER WINDSHIELD PANEL CRACKED.

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DURING PREFLT INSPECTION; FO TURNED ON WINDSHIELD HEAT WITH CAPT'S #1 WINDSHIELD OUTER PANE CRACKING IMMEDIATELY. MAINT WAS REQUESTED WHEREUPON IT WAS DETERMINED THAT THE ACFT (A B727 MODEL 100) COULD BE DISPATCHED WITH THE OUTER PANE CRACKED; WITHOUT ANY PENALTIES EXCEPT FOR THOSE LISTED IN THE PLT'S FLT MANUAL LIMITATIONS SECTION. SINCE IT WAS APPARENT TO MAINT PERSONNEL THAT THE WINDSHIELD HEAT TEMP CTLR WAS THE CAUSE OF THE PROB THE ACFT WOULD BE DISPATCHED WITH CAPT'S WINDSHIELD HEAT OFF. THE LIMITATIONS SECTION OF OUR FLT MANUAL PROVIDE FOR DISPATCH WITH NO MORE THAN ONE WINDOW HEAT INOP PROVIDED THE ACFT IS NOT DISPATCHED WITH KNOWN OR PROBABLE ICING CONDITIONS. SINCE NO ICING CONDITIONS WERE PRESENT ON INTENDED RTE OF FLT; WE DISPATCHED/FLEW TO DEST AFTER MAINT SIGNED OFF MY WINDSHIELD CRACKED WRITE-UP. AFTER THOROUGHLY REVIEWING THE FLT MANUAL SUBSEQUENT TO MY FLT WITH PARTICULAR ATTN TO THE LIMITATIONS SECTION; I BECAME LESS CONVINCED THAT I WAS RELEASED LEGALLY BY THE MECHS OR LEGAL TO DISPATCH A 100 MODEL B727 WITH A CRACKED OUTER 1 WINDSHIELD AND THE WINDSHIELD HEAT OFF. I BELIEVE THAT THE CIRCUMSTANCES THAT WOULD PERMIT SUCH A DISPATCH APPLY TO THE 200 MODEL AND THAT THE AMBIGUOUS PHRASEOLOGY IN OUR FLT MANUAL LEAVES SUCH MISINTERPRETATION VERY MUCH A POSSIBILITY. I PURSUED THIS THROUGH OUR COMPANY MAINT CTR AND AFTER EXPLAINING THE CIRCUMSTANCES WAS STILL UNABLE TO BE ADVISED WHETHER THE DISPATCH WAS LEGAL OR NOT. HAD IT BEEN ILLEGAL TO FLY THE ACFT UNDER THOSE CONDITIONS; I WOULD HAVE INDEED REFUSED TO DO SO. I INTEND TO TAKE THIS UP WITH MY CHIEF PLT AT FIRST OPPORTUNITY AND ARRIVE AT A DEFINITIVE AND ACCURATE ANSWER.