Regional Jet 200 ER/LR (CRJ200)
Maintenance Airframe; Maintenance Powerplant
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy
Aircraft Aircraft Damaged
Company Policy; Procedure; Manuals; Human Factors
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.
Maintenance Controller requested that deferral applicability for duct louvers be clarified.