Narrative:

I received a write up from the flight crew that the ramp had reported a crack in the cargo bay. I took the aircraft out of service; and dispatched maintenance to inspect the damage. Upon arrival; maintenance discovered a crack in the air conditioning ducting. I queried the database for previous instances of this defect in order to develop a plan of action consistent with successful actions taken in the past. During this search I discovered nef (non-essential furnishing) xx-xx-xx-xx was used to defer an identical defect. It stated that 'cargo compartment air conditioning vent louvers and screen may be damaged or missing.' I confirmed with the mechanic on the ground that it was an air conditioning duct and that it was a louver that was damaged and proceeded to place the duct on MEL (minimum equipment list).later the plane was taken out of service and a gmm (general maintenance manual) approved temporary repair was used to clear the nef and return the aircraft to service. I was later advised that there existed tribal knowledge that back when this nef was created it was intended to be applicable to a lower air conditioning duct (the one with a screen) but not the cargo compartment air conditioning duct damaged in this instance.without the benefit of tribal knowledge; a plain language interpretation of nef xx-xx-xx-xx would lead a reasonable person to believe that all cargo compartment duct louvers were eligible to be deferred and; in practice; have been deferred in the past. This distinction should be clarified in the nef.

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Original NASA ASRS Text

Title: Maintenance Controller requested that deferral applicability for duct louvers be clarified.

Narrative: I received a write up from the Flight Crew that the Ramp had reported a crack in the cargo bay. I took the aircraft out of service; and dispatched Maintenance to inspect the damage. Upon arrival; Maintenance discovered a crack in the air conditioning ducting. I queried the database for previous instances of this defect in order to develop a plan of action consistent with successful actions taken in the past. During this search I discovered NEF (Non-Essential Furnishing) XX-XX-XX-XX was used to defer an identical defect. It stated that 'Cargo compartment air conditioning vent louvers and screen may be damaged or missing.' I confirmed with the Mechanic on the ground that it was an air conditioning duct and that it was a louver that was damaged and proceeded to place the duct on MEL (Minimum Equipment List).Later the plane was taken out of service and a GMM (General Maintenance Manual) approved temporary repair was used to clear the NEF and return the aircraft to service. I was later advised that there existed tribal knowledge that back when this NEF was created it was intended to be applicable to a lower air conditioning duct (the one with a screen) but not the cargo compartment air conditioning duct damaged in this instance.Without the benefit of tribal knowledge; a plain language interpretation of NEF XX-XX-XX-XX would lead a reasonable person to believe that all cargo compartment duct louvers were eligible to be deferred and; in practice; have been deferred in the past. This distinction should be clarified in the NEF.

Data retrieved from NASA's ASRS site 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.