MLG HAS PBE EQUIP PROB WHICH IS MEL'ED. DISPATCH LATER FINDS THIS WAS NOT LEGAL.

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THE PIC CALLED IN FROM SMF WITH A MECHANICAL DISCREPANCY. DURING A FLT ATTENDANT CREW CHANGE THERE; AN ONCOMING FLT ATTENDANT NOTICED THE AFT PBE UNIT HAD AN EXTENDED VSI; AND FURTHER; HAD A 'SPONGY' FEEL TO IT; AND DID NOT MEET SVCABILITY REQUIREMENTS PER PROCS NOTED ON THE UNIT'S PLACARD. OUR MEL PAGE (DATED SEP/XX/94) STATES THAT ANY IN EXCESS OF THOSE REQUIRED BY FAR (4) MAY BE INOP. AS WE ONLY HAVE 4 INSTALLED; ALL 4 ARE REQUIRED. OUR MEL ALSO STATES THAT THE VSI MAY BE PROTRUDING (IT WAS) AND/OR 1 (OR BOTH) TAMPER EVIDENT SEALS MAY BE BROKEN OR MISSING PROVIDED THE PBE IS SVCABLE AS DETERMINED BY THE PBE CHK PROC PLACARD AFFIXED TO THE UNIT ITSELF; WHICH THE FLT ATTENDANT STATED WASN'T THE CASE. OUR MEL ALSO MAKES REF TO A MAINT DEPT DOCUMENT (MPD 127); WHICH IS PUBLISHED SEPARATELY; AND IS NOT READILY AVAILABLE TO LINE FLCS. I INITIATED A 3-WAY PHONE CONVERSATION BTWN MYSELF; THE PIC; AND THE MAINT CTLR; AND THE MAINT CTLR ALSO REFERRED TO THE MPD 127. I INSISTED THAT HE FAX ME A COPY; WHICH HE DID *(PAGES 1 AND 2); AND I ALSO FAXED A COPY TO THE PIC AT SMF. ONE OF THE MPD 127 PAGES WAS DATED NOV.XX.94 (SUBSEQUENT TO THE MEL PAGE); AND THE CHANGE BAR ON THIS NEWER PAGE MENTIONED THAT A 'SPONGY' PBE MUST BE REPLACED WITHIN 36 HRS OF DISCOVERY. ON THIS BASIS; THE PIC AND I CONCURRED ON VALIDITY OF THE MEL ITEM DEFERRAL; AND THE FLT OPERATED FROM SMF-LAX-LAS. A NEW PBE WAS INSTALLED AT LAS; AND THE LOGBOOK CLRED. FOLLOW-UP WITH TECHNICAL SUPPORT STAFF A FEW DAYS LATER INDICATED QUITE A BIT OF CONFUSION; MAINLY OVER WHICH DOCUMENT (MEL OR MPD 127) TAKES PRECEDENCE; AND WHETHER A 'SPONGY' PBE IS ACTUALLY A SVCABLE ONE; AND THUS LEGAL FOR DISPATCH. THE MPD 127 ALSO HAD A 3RD AND 4TH PAGE (NOT FAXED AT THE TIME OF THE ORIGINAL INCIDENT) AND IT MENTIONS THAT A 'HARD' PBE IS SVCABLE; THUS ONE COULD REASONABLY CONCLUDE THAT A 'NON- HARD' (IE; SPONGY) PBE IS NOT SVCABLE. IF TRUE; THIS WAS NOT A LEGAL DEFERRAL; THUS THIS RPT. IN CLOSING; MY OPINION IS THAT SITS SUCH AS THESE COULD BE MINIMIZED IF AIRLINE MGMNT WOULD WORD AND OTHERWISE CONSTRUCT OPERATIONAL MANUALS TO BE AS SPECIFIC AS POSSIBLE; RATHER THAN TO IMBED 'FLEXIBILITY' THAT CAN BE INTERPRETED FAR TOO LIBERALLY. ADDITIONALLY; ALL APPLICABLE INFO SHOULD BE INCLUDED INTO THE LINE OPERATING MANUAL (MEL; IN THIS CASE) RATHER THAN REFED TO MORE OBSCURE MANUALS THAT ARE NOT IMMEDIATELY AVAILABLE TO PIC'S AND DISPATCHERS.