LIFING / RELIFING OF A/C OMPONENTS- ANY GUIDELINES ? 1

[ZeeS]

Hello all.....

I am maintaining a fleet of five aircrafts. recently I have got a study to redefine the life of some of the components, based upon some occurrences we had in past few years... the aircraft has a very mature history and is being maintained under RCM analysis by USAF.

now I do not consider this size of fleet to accurately or even approximately get close to what usaf has already defined.

I went thru MIL1530C, which talks about ASIP, but could not find any thing related to sample size of aircrafts or guideline for component lifing.

so, is there any document / paper / literature that gives guide lines on how to define (and redefine) the life of components installed on aircraft.
thanks in advance.

 

[rb1957]

lifing a part is easy ... fatigue analysis based on average usage

re-lifing is harder ... compare anticipated usage with experienced usage, re-calc fatigue ...

Quando Omni Flunkus Moritati

 

[ZeeS]

well..... it would have been a lot simpler had these been structural parts..... these are system components (including airframe, hydraulic and specially prop controls)....so no point in stress analysis....

 

[rb1957]

for systems components, research CMR (certification Maintenance Requirements) and MSG-3.

structures have developed a logic for reducing safe life factor depending on the sample size (from statistical analysis of an assumed population dist'n)

why does a system's component have a safe-life ? aren't these normal "retired for cause" ('cept of landing gear).

if you're relifing a component than look at the original basis for the life declared, and see how you can logically and reasonably argue that your experience has been less damaging.

Quando Omni Flunkus Moritati

 

[kontiki99]

Some parts are replaced on condition. It's fine if you can accept the impact to dispatch reliability. Assigning everything a hard time is more expensive, but can help your readiness numbers improve.

In theory, there is no difference between theory and practice; experience suggests that in practice, there is.