A couple of our customers have come into the ALN facility with TLMC Section 5-10-30, Chapter 5 Task #57-10-00-114* Special Detailed Inspection of the Lower Wing Plank at the Rear Spar as a due item. Per the Maintenance Planning Document, the task threshold is 5,100 landings, and the man hours outlined in the MPD is two hours to complete the task with no hours allocated to access. The 5,100 landing milestone does not usually line up with an adequate monthly or hourly inspection to facilitate optimal downtime and cost overlay. What we have encountered is customers asking to complete this due item with a small inspection when the aircraft would be at our facility for five days or less.

This task incorporates three NDT tasks to complete: ET-57-20-019 Special Detailed Inspection of the Lower Wing Plank at the Rear Spar WS59.00 to WS65.00; ET-57-20-020 Special Detailed Inspection of the Lower Wing Plank at the Rear Spar WS59.00 to WS65.00 (Bolt Holes); and UT-57-20-001 Special Detailed Inspection of the Rear Spar Web Lower Fasteners Common to the MLG Trunnion Fitting Inboard and Outboard of WS65.75. 

Each of these tasks adds inspection and access time. ET-57-20-019 requires additional inspection time for the Non-Destructive Testing. 

ET-57-20-020 requires access to four fuel panels. This means the aircraft must be defueled and sumped, then the fasteners cleaned and removed, and finally the Non-Destructive Testing must be performed. A total of 16 fasteners must be cleaned, removed, and tested. These fasteners must be removed one at a time and replaced with a new one. The area then gets resealed, closed, and leak-checked. 

UT-57-20-001 requires the removal of the hydraulic cover in the wheel well. Then each fastener has to be ultrasonic tested. 

The confined workspace limits the manpower accessibility, and because of the extent of the NDT testing (inspections), this becomes a labor-intensive job and increases unexpected costs and downtime.   

Planning ahead and completing this task with a larger inspection requiring downtime of seven business days plus and/or when the aircraft is needing to be defueled for maintenance can reduce the impact of additional downtime and cost. The larger inspection incorporating aircraft defueling and access to these panels includes the 96-month, the 48-month after the first 96-month inspection, and the 4,800 landing inspection, which combines seven tasks, at least one of which requires accessing the same panels and defuel.