The phased inspection program for LFEC is derived as follows:
Add the ΔDTR values for the visual inspections 0.5 +0.4 + 0.3 = 1.2.
Subtract this value from the REQUIRED DTR = 4 - 1.2 = 2.8. This gives the ΔDTR that is required
from the LFEC inspections. Note that a ΔDTR = 3.0 corresponds to N = 20,000 for the Direction 3 -
LFEC line.
For convenience, assume N = 20,000 (2 x D-Check) giving ΔDTR = 3.0, and enter these values under
N = 100 F/RO and ΔDTR, respectively.
Select a convenient interval for conducting the LFEC inspections: F = 10,000 flight cycles (D-Check).
Determine the number of aircraft in the phased inspection (Ro = 100F/N = 50 percent) and enter this
value under %PHASE Ro.
Add the ΔDTR values 0.5 + 0.4 + 0.3 + 3.0 = 4.2.
This value exceeds the REQUIRED DTR of 4; therefore, the program is satisfactory. For this SSI the
operator must conduct the visual inspections on all eligible airplanes with the intervals and methods shown. In addition, the SSI must receive an LFEC inspection on any 5 of the 10 eligible airplanes by 10,000 flight cycles. The remaining 5 eligible airplanes must be inspected by 20,000 flight cycles. This sequence is then repeated.
Examples of phased inspection programs are given on Pages 7.0.23 through 7.0.29 as follows:
Phased Inspection Example A - (EX-2)
Operator has 10 eligible airplanes and a D-check cycle of 10,000 flight cycles. To obtain an adequate
DTR, an LFEC inspection is required with N = 20,000 flight cycles. The operator proposes to inspect
EX-2 during D-checks utilizing a phased inspection program.
The sequence for the eligible airplanes to visit the maintenance base for a D-check, after starting the
supplemental inspection program, is shown on Page 7.0.23. A typical phased inspection program with
Ro = 100 (10,000/20,000) = 50 percent is shown on Page 7.0.24.
Phased Inspection Example B - (EX-2)
The values are derived as in Example A, but operator’s D-check cycle is 5,000 flight cycles. See
Pages 7.0.25 and 7.0.26.
Phased Inspection Example C -(EX-2)
The values are derived as in Example A, except operator has four eligible airplanes and a D-check cycle
of 15,000 flight cycles. See Pages 7.0.27 and 7.0.28.
Phased Inspection Example D -(EX-2)
The values are derived as in Example B, except that the operator’s D-check is 15,000 flight cycles and
there is an interval of 10,000 flight cycles between successive D-check visits of the 10 eligible airplanes.
During this time, the ineligible airplanes receive a D-check.
The average interval between successive visits of the eligible airplanes is approximately 15,000 flight
cycles, given the number of aircraft in the phased inspection of Ro = 100 x 15,000/20,000 = 75 percent.
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