Narrative:

On arrival at the aircraft, there was a maintenance carryover item regarding MEL #36-11-02. A discussion with the maintenance coordinator and dispatcher ensued regarding the high pressure shutoff valve for the right engine, which was shown as inoperative. There was also a note C associated with this item in the MEL. The note stated, 'descent, approach and landing are not made in icing conditions within 5000 ft AGL.' in trying to ascertain from the dispatcher and maintenance coordinator confirmation if item C applied to our situation or not because we needed both engine anti-ice and airfoil anti-ice, they would not commit. They were focused on the 'expected' icing level and avoided the issue of our concern which was that our manuals (operations manuals) state that engine anti-ice must be used with outside air temperature below 10 degrees tat (50 degrees F) and below, and I knew we would need it below 5000 ft AGL. Our whole issue was if item C was applicable to engine anti-ice. After further discussion, we were assured by maintenance coordinator that engine anti-ice and airfoil anti-ice would function, and be in compliance with the MEL. After takeoff from ZZZ, en route to ZZZ1, the captain and I started to research further in the MEL. We decided to send a message to the dispatcher to clarify again that the use of engine anti-ice was not limited by note C in the MEL. The dispatcher could not convey the assurance we needed to continue in known icing conditions. Without this assurance and in the interest of safety, we felt the prudent decision was to divert and not continue into the icing conditions present at ZZZ1. Callback conversation with reporter revealed the following information: the reporter stated the note C in the MEL was misleading as engine anti-icing is supplied from the low pressure compressor stage and is not supplied from the high stage bleed. The problem in this situation was dispatch and maintenance would not make a decision and in the state of the carrier today no one wants to make the wrong decision.

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Original NASA ASRS Text

Title: A B757-200, WITH THE R ENG HIGH PRESSURE BLEED VALVE DEFERRED CLOSED PER THE MEL, DIVERTED DUE TO MISINTERP OF MEL NOTE C AND NON COMMITMENT BY MAINT AND DISPATCH TO MAKE A DECISION.

Narrative: ON ARR AT THE ACFT, THERE WAS A MAINT CARRYOVER ITEM REGARDING MEL #36-11-02. A DISCUSSION WITH THE MAINT COORDINATOR AND DISPATCHER ENSUED REGARDING THE HIGH PRESSURE SHUTOFF VALVE FOR THE R ENG, WHICH WAS SHOWN AS INOP. THERE WAS ALSO A NOTE C ASSOCIATED WITH THIS ITEM IN THE MEL. THE NOTE STATED, 'DSCNT, APCH AND LNDG ARE NOT MADE IN ICING CONDITIONS WITHIN 5000 FT AGL.' IN TRYING TO ASCERTAIN FROM THE DISPATCHER AND MAINT COORDINATOR CONFIRMATION IF ITEM C APPLIED TO OUR SIT OR NOT BECAUSE WE NEEDED BOTH ENG ANTI-ICE AND AIRFOIL ANTI-ICE, THEY WOULD NOT COMMIT. THEY WERE FOCUSED ON THE 'EXPECTED' ICING LEVEL AND AVOIDED THE ISSUE OF OUR CONCERN WHICH WAS THAT OUR MANUALS (OPS MANUALS) STATE THAT ENG ANTI-ICE MUST BE USED WITH OUTSIDE AIR TEMP BELOW 10 DEGS TAT (50 DEGS F) AND BELOW, AND I KNEW WE WOULD NEED IT BELOW 5000 FT AGL. OUR WHOLE ISSUE WAS IF ITEM C WAS APPLICABLE TO ENG ANTI-ICE. AFTER FURTHER DISCUSSION, WE WERE ASSURED BY MAINT COORDINATOR THAT ENG ANTI-ICE AND AIRFOIL ANTI-ICE WOULD FUNCTION, AND BE IN COMPLIANCE WITH THE MEL. AFTER TKOF FROM ZZZ, ENRTE TO ZZZ1, THE CAPT AND I STARTED TO RESEARCH FURTHER IN THE MEL. WE DECIDED TO SEND A MESSAGE TO THE DISPATCHER TO CLARIFY AGAIN THAT THE USE OF ENG ANTI-ICE WAS NOT LIMITED BY NOTE C IN THE MEL. THE DISPATCHER COULD NOT CONVEY THE ASSURANCE WE NEEDED TO CONTINUE IN KNOWN ICING CONDITIONS. WITHOUT THIS ASSURANCE AND IN THE INTEREST OF SAFETY, WE FELT THE PRUDENT DECISION WAS TO DIVERT AND NOT CONTINUE INTO THE ICING CONDITIONS PRESENT AT ZZZ1. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE NOTE C IN THE MEL WAS MISLEADING AS ENG ANTI-ICING IS SUPPLIED FROM THE LOW PRESSURE COMPRESSOR STAGE AND IS NOT SUPPLIED FROM THE HIGH STAGE BLEED. THE PROB IN THIS SIT WAS DISPATCH AND MAINT WOULD NOT MAKE A DECISION AND IN THE STATE OF THE CARRIER TODAY NO ONE WANTS TO MAKE THE WRONG DECISION.

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.