B737 Next Generation Undifferentiated
Maintenance Powerplant
Confusion; Situational Awareness; Communication Breakdown
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Logbook Entry; Manuals; Procedure; Chart Or Publication; Human Factors; Aircraft
[This is in] regards to the reported incident involving a B737 NextGen aircraft Number 1 Engine. I honestly do not remember the exact conversation; I recall a discussion about Alodine coating being worn or missing but do not recall if it was this incident; however I do know had I understood the [fan] case parent metal may have been damaged I would have taken different action. I have reviewed the Deferred Items; the log pages; the picture of the damage when the deferral was issued and the picture that was taken at the time of engine removal. The initial picture indicates one area of damage to the abradable [material] and although the focus is a little grainy I don't believe there is evidence of parent metal damage. The picture taken at the time of engine removal indicates two areas of abradable damage with the parent metal clearly damaged. Neither of the log pages against this aircraft indicated parent metal damage; only that it was exposed. This is the reason we require pictures or drawings describing the damage. On my shift beginning early evening and ending the following morning; I was involved with two aircraft with abradable shroud damage resulting in four maintenance write-ups for deferral. I issued total of twelve deferral write-ups during that shift. Damage to the abradable shroud on the General Electric (GE) CFM-56 engines and the attrition liner on the Rolls Royce engines is quite common since this is a sacrificial material that is used to protect the parent metal of the case. The deferral process for this type of damage on the B737-7/8/9 is found in the Boeing AMM 72-24-02-200 and has been the source of many discussions with [our Air Carrier's] Power Plant Engineering in regards to interpretation of damage and the amount of damage that can be deferred. This section of the Maintenance Manual (M/M) has been revised several times and there is currently a case presented to GE for further clarification (not concerning this incident). The damage to fan case parent material is covered in AMM 72-24-01-200; since this is part of the fan burst containment area there is very little damage (.0039 thousandths of an inch; in depth) allowed. I have spoken to Power Plant Engineering and requested a link be added to the Abradable Shroud Inspection section; linking the Fan Inlet Case Inspection to it gives better visibility of the allowed fan case parent metal damage. Personally; I will request better pictures of the damage and an overall picture to pinpoint exactly where the damage has occurred.
An Aircraft Maintenance Technician (AMT) reports on his perspective of damage he previously found on an abradable shroud at the fan inlet case of a General Electric (GE) CFM-56 engine on a B737 NextGen aircraft that was different from the damage noted during engine removal. Damage had extended through the abradable shroud into the fan case parent material.