Section 1.3.6.3. Fail Safe Crack Arrest Structures
Fail safe crack arrest structure must be able to withstand a
specified period of service usage after a primary load path failure. The period of unrepaired service usage
depends upon the inspectability level for the structure. The degrees of inspectability for fail safe
crack arrest structure are the same as for fail safe multiple load path
structures.
The initial inspection intervals are given in Table 1.3.5, and
subsequent inspection intervals are given in Table 1.3.6.
Table 1.3.6. Subsequent In-Service Inspection Intervals
for Fail-Safe Structures
|
Primary Element Degree of Inspectability
|
Pxx
|
Subsequent Inspection Intervals
|
|
In-Flight Evident
|
PFE
|
Each flight of most
damaging design mission
|
|
Ground Evident
|
PGE
|
Two flights of most
damaging design mission
|
|
Walk-Around Visual
|
PWV
|
Ten flights of most
damaging design mission
|
|
Special Visual
|
PSV
|
One year
|
|
Depot or Base Level
|
PDM
|
One half of the remaining
time to failure of the adjacent structure from the flaw size specified for
adjacent load paths at the time of primary element failure; or, if the
adjacent structure is inspected, one
half of the remaining time to failure
of the adjacent structure from in-service inspection flaw size for the
adjacent structure as specified. In
either case, the primary element is assumed to be failed.
|