B767 CREW OBSERVED THE MEL THAT DEALT WITH AN INOP PNEUMATIC BLEED VALVE THAT DID NOT PRODUCE THE DESIRED AFFECT.

Narrative

SLOW GEAR RETRACTION AFTER MEL ALLOWED TKOF WITHOUT WT PENALTY. NOTICED THE L BLEED ISOLATION VALVE LIGHT ILLUMINATED JUST PRIOR TO PUSHBACK. CYCLED SWITCH WITH NO EFFECT. DECIDED TO SEE IF ENG START WOULD GET IT WORKING. AFTER START; VALVE LIGHT ON THE SWITCH WENT OUT BUT WAS STILL ILLUMINATED ON EICAS. BACK TO THE GATE. MAINT OPTED TO SWAP L AND CTR ISOLATION VALVES AND PLACARD THE CTR VALVE UNDER MEL 36-4C. THE MEL PROCS SPECIFIES A 40000 LB PERFORMANCE PENALTY IF THE APU WILL NOT BE USED AS AN AIR SOURCE FOR THE AIR DRIVEN PUMP. SINCE THE APU WAS AVAILABLE AS AN AIR SOURCE; WE SAW NO REASON TO APPLY THE PENALTY AND DISPATCH CONCURRED. UPON GEAR RETRACTION WE OBSERVED PRESSURE LIGHTS IN THE CTR SYS AND A LONGER THAN NORMAL RETRACTION CYCLE. THE CYCLE WAS LONGER; BUT NOTHING LIKE THE BOOK SPECIFIES OF UP TO 1 MIN. DISCUSSED THE RETRACTION AND CONTACTED MAINT TECHNICIAN VIA SATCOM. (WAS THE CTR SYS PERFORMANCE AS IT SHOULD BE OR WAS THERE A PROB WITH APU AIR CUTTING TO THE ADP?) MAINT THEN ASSURED US THE PROCS TO CLOSE THE CTR ISOLATION VALVE WERE CORRECTLY ACCOMPLISHED (CORRECT CIRCUIT BREAKERS COLLARED; ETC). BUT MAINT DID NOT KNOW IF A MANUALLY CLOSED CTR ISOLATION VALVE WOULD SATISFY APU BLEED VALVE LOGIC AND ALLOW IT TO OPEN/PROVIDE AIR TO THE ADP. ALSO; PLACARDING THE CTR ISOLATION VALVE REQUIRES THAT THE HYD GENERATOR BE PLACARDED UNDER MEL 24-13. IN ACCORDANCE WITH MEL; FOR THE ETOPS PORTION OF THE FLT; WE WERE REQUIRED TO RUN THE APU. THIS WOULD IMPLY A SHUTDOWN OF THE APU UPON COASTING IN. WHAT ABOUT LNDG AND THE ADP AIR? IT SEEMS THAT BOTH THESE PROCS ARE LACKING IN INFO AND GUIDANCE. IT SETS THE STAGE FOR NUMEROUS SURPRISES.