Line aircraft technician reported finding excessive damage to cargo pit sidewalls in a B737-900 due ...

Narrative:

[Maintenance technicians were] dispatched to aircraft to evaluate damage to the sidewall liners in the aft pit right/H side. We found unserviceable liners based on amm 25-52-01 (holes larger than 1.5'). This is not the first aircraft in the last two weeks that had to have MEL applied due to excessive damage to the sidewall liners. The damage appears to be frame by frame progressive over time. The question is; when is it now unserviceable and when does the ramp decide it's time to call it in? It seems these holes are out of limits long before the call is made. That would be an unsatisfactory condition for flight based on amm 25-52-01; far 25.855 and far 25.853. Two more aircraft come to mind that I was involved with in the last two weeks. These also required MEL in order to release the aircraft. Both had damaged right/H sidewall liner damage that appears to be progressive. Normal wear with lack of aggressive inspection intervalsincrease inspection intervals by mechanics. Educate ramp. Apply a strip of 'pile velco' (sticky back) to the rivets on each frame where wear occurs. This acts as a barrier between the liner and frame button head rivets. It's these rivets that are wearing through the liner.

Original NASA ASRS Text

Title: Line Aircraft Technician reported finding excessive damage to cargo pit sidewalls in a B737-900 due to wear from rivet heads on the frame. He found holes larger than 1.5 inches which exceeded the limit in the FARs.

Narrative: [Maintenance technicians were] dispatched to aircraft to evaluate damage to the sidewall liners in the aft pit R/H side. We found unserviceable liners based on AMM 25-52-01 (holes larger than 1.5'). This is not the first aircraft in the last two weeks that had to have MEL applied due to excessive damage to the sidewall liners. The damage appears to be frame by frame progressive over time. The question is; when is it now unserviceable and when does the ramp decide it's time to call it in? It seems these holes are out of limits long before the call is made. That would be an unsatisfactory condition for flight based on AMM 25-52-01; FAR 25.855 and FAR 25.853. Two more aircraft come to mind that I was involved with in the last two weeks. These also required MEL in order to release the aircraft. Both had damaged R/H sidewall liner damage that appears to be progressive. Normal wear with lack of aggressive inspection intervalsIncrease inspection intervals by Mechanics. Educate Ramp. Apply a strip of 'Pile Velco' (sticky back) to the rivets on each frame where wear occurs. This acts as a barrier between the liner and frame button head rivets. It's these rivets that are wearing through the liner.

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.

Attributes
ACN	1370601
Time
Date	201607
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Light	Dawn
Aircraft 1
Make Model Name	B737-900
Operating Under FAR Part	Part 121
Flight Phase	Parked
Flight Plan	IFR
Component
Aircraft Component	Cargo Compartment Sidewall Panel
Person 1
Function	Technician
Qualification	Maintenance Airframe Maintenance Powerplant
Events
Anomaly	Deviation - Procedural FAR Deviation - Procedural Published Material / Policy Deviation - Procedural Maintenance

Line aircraft technician reported finding excessive damage to cargo pit sidewalls in a B737-900 due to wear from rivet heads on the frame. He found holes larger than 1.5 inches which exceeded the limit in the fars.