AN EMB145 CAPT RPTS BEING DISPATCHED WITH #2 ANTI-ICE VALVE FAILED AND DEFERRED PER THE MEL; AND CLAIMS THAT THE MEL AND EMB POH GIVES NO OPERATIONAL DATA ON CLB; CRUISE; DSCNT AND ALT RESTRICTION DUE TO LOWER ENG PERFORMANCE.

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ON NOV/SAT/2006; I HAD RECEIVED ACFT X IN ZZZ WITH MEL 30-21-01-1 PERTAINING TO ENG 2 ANTI-ICING VALVE FAIL (E2 A/I VLV FAIL). THE PORTION OF THE MEL THAT I WOULD LIKE TO FOCUS ON REGARDING THE SELECTION OF 'ENG' ON THE ICING PANEL OVERRIDE SELECTOR. I HAD CONVERSED WITH A MAINT CTLR DURING THE FLT AND A COUPLE OTHER COLLEAGUES TO FURTHER EXPLAIN MY SITUATION ENCOUNTERED PRIOR TO FILING THIS RPT. THE FLT CREW OPERATING PROC PER THE MEL; AS REMEMBERED; STATES THAT A 'TO' TKOF MUST BE USED; REF A/I SELECTED 'ON;' AND THE OVERRIDE KNOB TO BE SELECTED TO 'ENG.' HOWEVER; IT DOES NOT STATE WHETHER OR NOT TO RE-SELECT THE 'AUTO' POSITION OF THE OVERRIDE KNOB ONCE AIRBORNE WHEN COMPARED TO THE NORMAL OPERATIONS WITH ICING CONDITIONS ENCOUNTERED ON THE GND. ADDITIONALLY; THE MEL STATES THAT IF THE 'E2 A/I VLV FAIL' MESSAGE PERSISTS/RETURNS TO CONTACT MAINT. I COMPLIED WITH THE MEL FOR THE TKOF. ONCE AIRBORNE; I DECIDED TO SEE IF I WOULD RECEIVE THE FAIL MESSAGE BY SELECTING THE 'AUTO' POSITION. I DID RECEIVE THE FAIL MESSAGE AND DECIDING THE RETURN THE OVERRIDE KNOB BACK TO 'ENG' POSITION AND CONTINUE THE FLT. I CHKED THIS ONCE DURING CLB AND AGAIN AT LEVEL OFF ALT. WITH THIS IN MIND; IT CAUSED SOME CONCERN FOR ME DUE TO THE FACT THAT OUR CLB AND CRUISE PERFORMANCE WERE SIGNIFICANTLY REDUCED. THE CLB RATE AND FORWARD SPD WERE NOTICEABLY REDUCED AND ONCE AT FILED LEVEL OFF ALT (FL330); THE ACFT STABILIZED AT MACH .68/IAS 240; THRUST LEVERS IN THE THRUST SET DETENT; AND CLB POWER MODE SELECTED. WITH MY SYSTEMS KNOWLEDGE; ONCE THE ANTI-ICING SYSTEM IS ACTIVATED; THE AVAILABLE THRUST IS REDUCED TO ACCOMMODATE FOR THE ADDED REQUIREMENT TO PROVIDE SUFFICIENT AIR TO THE HEAT SURFACES SELECTED. THE MEL ALSO INFORMS US TO EXPECT TWO ADDITIONAL EICAS MESSAGES: 'NO ICE-A/ICE ON' AND 'ENG A/ICE OVERPRES;' WHICH WERE PRESENTED DURING THE FLT. APPROX SIX PERCENT N1 IS NOT AVAILABLE WHEN THE ANTI-ICING SYSTEM IS SELECTED NOTICED DURING THE SELECTION BETWEEN 'ENG' AND 'AUTO.' HOWEVER; IF I HAD DECIDED TO SELECT 'AUTO' ON THE OVERRIDE; I FELT THAT I WOULD BE IN DIRECT CONTRADICTION OF THE FLT CREW OPERATING PROC FOR THIS MEL. ONCE THE ACFT WAS STABILIZED AT FL330; ABOUT 15 MINS; WE WERE ONLY ABLE TO ACCELERATE TO THE ABOVE MENTIONED AIRSPD AND POWER CONFIGURATION. I THEN ENTERED THE NEW CRUISE SPD INTO PAGE 3 OF THE 'PERF INIT' PAGE IN THE FMS. AFTER THE FMS COMPUTED THE CURRENT CONDITIONS; I WAS SURPRISED TO SEE THAT WERE ONLY CAPABLE OF MAINTAINING FL333; WE WERE LEVEL AT FL330. I THEN DECIDED TO CONTACT DISPATCH WITH THE SITUATION AND ALSO CONFER WITH MAINT CTL. ONCE CONNECTED TO MAINT CTL; IT WAS BOTH AGREED UPON AS TO POSITION OF THE OVERRIDE KNOB; KEEPING IN THE 'ENG' POSITION. WITH THE NEW DATA IN THE FMS; I WAS NOT CONCERNED WITH THE AMOUNT OF FUEL REQUIRED FROM WHAT I HAD ONBOARD. PART TWO OF THIS SITUATION HIT ME WHEN WE WERE DSNDING INTO ZZZ1. SINCE THE ANTI-ICING IS NOW SELECTED; YOUR FLT IDLE IS NOW INCREASED AS WELL BY APPROX 20 PERCENT. THIS REQUIRES EXTRA DSCNT PLANNING DUE TO THE ADDED INABILITY TO DSND NORMALLY. SPD BRAKES AND FLAPS 9 (SPD AND ALT PERMITTING) WOULD BE REQUIRED TO AID IN THE DSCNT WITH THE ADDITIONAL THOUGHT OF EXTENDING THE LNDG GEAR TO RESET THE POWER BACK TO NORMAL FLT IDLE POWER. SO IN ESSENCE; YOU ARE NOT ACTUALLY CONDUCTING A NORMAL FLT IDLE DSCNT PER THE PROFILE USED DURING THE DISPATCHER'S PREFLT PLANNING. PART 3 WOULD BE FOR THE SUPPLEMENTAL OPERATIONS MANUAL WITHIN THE AIRPLANE. WHEN RESEARCHING THROUGH THIS MANUAL; ONLY THE HOLDING CHARTS REFERENCE WHETHER OR NOT THE ANTI-ICING SYSTEM IS ON OR OFF. NEITHER THE CLB; MAX CRUISE; LONG RANGE CRUISE; NOR THE DSCNT PLANNING CHARTS REFERENCED THE ANTI-ICING ON OR OFF ONLY BLEED OPEN. I FEEL THAT THIS INSUFFICIENT INFO CAUSES A LEGITIMATE SAFETY CONCERN DUE TO THE FACT THAT YOUR FUEL BURN COULD BE SIGNIFICANTLY DIFFERENT FROM THAT PROVIDED TO YOU BY THE DISPATCHER. PART 4 PERTAINS TO THE MINIMUM TEMP FOR MANUAL ANTI-ICING OF MINUS 40 DEG CELSIUS. MY QUESTION WOULD BE IS IF THIS LIMITATION PERTAINS TO THIS SCENARIO OR DOES THAT PERTAIN TO UTILIZING THE 'ALL' POSITION. IF IT PERTAINS TO BOTH 'ENG' AND 'ALL;' THEN YOU ARE NOT TEMP-ALT LIMITED. SO IN REVIEW: 1) DO YOU SELECT 'AUTO' ONCE AIRBORNE? 2) IF NOT; HOW CAN WE TRULY KNOW WHAT OUR EXPECTED FUEL BURN COULD BE? 3) WHAT IS THE MAXIMUM ALT PER A GIVEN WT? 4) IS THIS MINUS 40 DEG LIMITATION A LEGITIMATE QUESTION (ENG OR AUTO OR EITHER)? 5) IF MY CONCLUSION IS CORRECT; CONSULT EMBRAER REGARDING THIS AND POSSIBLY ADD AN ADDENDUM TO THAT PARTICULAR MEL. 6) ADDRESS YOUR FINDINGS WITH THE PLT GROUP IF THEY ARE PERTINENT AND SAFETY RELATED.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE MEL AND THE CHARTS IN THE PLT'S HANDBOOK GIVE NO PLANNING DATA FOR CLB; MAX CRUISE; LONG RANGE CRUISE NOR THE DSCNT WITH ENG ANTI-ICE BLEED VALVES OPEN. THIS AIRPLANE WAS ALT RESTRICTED AND THE LOWER PERFORMANCE WAS NOTICEABLE. IN DSCNT; THE FLT IDLE SPD WAS 20 PERCENT HIGHER; MAKING FOR AN ABNORMAL DSCNT PROFILE.