For the selected DETAIL, INSPECTION METHOD and DIRECTION, and a desired level of ΔDTR determine the value of N from the corresponding line in Block 6. This is similar to STEP 7, Option b).
Enter these values in Block 16 and 18, respectively.
Enter the desired inspection interval, F, in flight cycles, in Block 15.
Original D6-82669 7.0 DOCUMENT USAGE
Determine the PERCENT of aircraft to be inspected at each PHASE by solving Ro = 100F/N and enter this value in Block 14. This gives the percentage of the eligible fleet to be inspected within the interval, F.
ALTERNATIVELY having N and ΔDTR, the inspection interval, F, can be determined for a pre-selected value of Ro by solving F = N x Ro/100.
Option f) Any Combination of the Above
Operators can combine any of the Options a) through d) with their existing maintenance program to achieve the REQUIRED DTR. In many cases inspection intervals will be determined by minimum zone access for the most critical detail. This will generally result in a higher DTR than required for the remaining SSIs in the same inspection zone. For these items a phased inspection program can be adopted which meets or exceeds the REQUIRED DTR.
7.0 DOCUMENT USAGE D6-82669 Original
7.4 DTR System Examples
The following section contains examples of the use of the DTR system and phased inspection. Although the examples are typical, they do not represent any actual airplane structure, model or operator. (Completed example DTR Check Forms for all SSIs are contained in Section 8.)
7.4.1 EXAMPLE 1
SSI - FORWARD FUSELAGE CROWN SKIN AND STRINGER, EXISTING MAINTENANCE ON 36 AIRPLANES (10 ELIGIBLE AIRPLANES):
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EXTERNAL GENERAL VISUAL AT C-CHECKS EVERY 2,500 FLIGHT CYCLES.
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INTERNAL GENERAL VISUAL ON 50 PERCENT OF ELIGIBLE A/C AT D-CHECKS EVERY 10,000 FLIGHT CYCLES.
REQUIRED DTR = 6.
The completed DTR Check Form is shown on Page 7.0.13.
The values are derived as follows:
SKIN, INSPECTION DIRECTION 1, GENERAL VISUAL
The inspection is conducted every C-check, so enter C under CHECK LEVEL.
All airplanes are inspected, enter 100 under % PHASE Ro.
C-check corresponds to 2,500 flight cycles, so enter 2,500 under FREQUENCY.
All airplanes inspected N = F, enter 2,500 under N = 100 F/Ro.
Enter ΔDTR vs. N chart at N = 2,500 flight cycles.
Read ΔDTR from DIRECTION 1 GENERAL VISUAL line.
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