.
Check level change (e.g., more frequent inspections, D-check to 4C-check or 4C-check to 2C-check, etc.).
.
Additional visual inspections from other zones or directions.
.
Use of NDT procedures.
.
Any combination of the above.
5.1.7 This document defines inspections for SSIs with no known service history of fatigue cracking. SSIs with a history of fatigue cracking are referenced in Section 9.0 of this document along with associated Service Bulletins (SBs).
Original D6-82669 5.0 DTR SYSTEM APPLICATION
5.1.8 The average utilization of each operator's eligible1 fleet can be used to determine equivalent scheduling for repeat inspection intervals in flight cycles, flight-hours or calendar time. Repeat inspection intervals can be based on either the approved scheduled intervals or the fleet average intervals. The repeat interval for supplemental inspections of individual airplanes can vary within plus 10% of the flight cycles needed to achieve the required DTR.
5.1.9 To minimize manpower requirements, details with similar repeat intervals, common access or other similarities can be grouped into packages. The repeat interval for the package shall be no greater than the shortest repeat interval for any SSI in the package.
5.1.10 Each inspection method considered for an SSI or group of SSIs shall be scheduled as a separate task. Multiple inspections of the same structural detail from the same direction using the same inspection method during a single repeat interval are not valid for DTR calculations. General visual and detailed inspections are considered a single inspection unless accomplished at different check levels.
5.1.11 Inspections shall be accomplished at F frequency associated with the specified check level (A, C, D or equivalent). F may not exceed the frequency of the operator's major structural inspection interval (D check or equivalent). The value of F should not exceed 30,000 flight cycles.
. If N is equal to F, all eligible airplanes shall be inspected at a frequency no greater than F.
5.1.12 The principal structural details and critical cracking pattern for each SSI are shown in the diagram on the DTR Check Form. The cracking pattern shown is not necessarily the pattern that may occur. For example, a crack may originate in the opposite side of an SSI to the one shown. Therefore, all visible parts of the SSI detail(s) should be inspected. The inspection options shown for each SSI provide adequate opportunity for detecting fatigue damage from any pattern.
5.1.13 A General Visual Inspection (GVI) of visible adjacent structure shall be conducted during inspection of a given SSI. Credit for these GVIs permitted a reduction in the total number of DTR Check Forms required.
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