In this section is
where the operators find information about the parts in the aircraft
that are classified as Life Items.
A manufacturer
determines when a part is a life item after the part goes through
rigorous test. The part endures stress tests, temperatures tests,
reliability tests, corrosion tests to mention some of them.
A life items is an item
that after being in service in the aircraft for a certain period, it is
not longer safe to keep operating in the aircraft when it reaches its
maximum safe life. Some parts could be classified as life items after
years of being in service through Airworthiness Directives. The
Airworthiness Directive requires the urgent attention of the operators
and is generally limited to items affecting safety.
Depending where the
part is installed on the aircraft, a part may be life limited by cycles
(take offs and landings) or by hours in service. The landing gear life
limited parts is determined by the cycles in the majority of the cases.
Life limited parts in
an engine are tracked by hours of operation rather than cycles. This
tracking method is also used on the spindle carriage in the wings of
some aircraft models.
The life limited parts
are usually serialized with the solely purpose to maintain control of
the part. The operator is ought to keep record of the part from the time
the part it was manufacturer. This documentation or record is known as
“Back To Birth Traceability”.
Back To Birth
Traceability is a documentation that clearly demonstrate every owner and
installation of the part where lists the specific aircraft number,
aircraft weight class, hours and cycles all the way back to the time the
part was manufactured.
Initially, a part may
not be considered s life item. However, if the part fails in service
because of fatigue then the FAA forces the aircraft manufacturer through
service bulletins and airworthiness directives to classify the part as
life item. This new classification poses a challenge to the operators
because there is no tracking records for the “new life item”.
In some cases, the operator decides to remove part from service
because they are not able to generate a Back To Birth Certificate for
the new “life” item. This decision proves costly to operators in some
cases but fortunately, for operators some manufacturers provide formulas
to calculate possible times and cycles for parts that lack of
Back To
Birth Traceability document.