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[TowerTalk] Failures due to preventative maintenance?

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Subject: [TowerTalk] Failures due to preventative maintenance?
From: (
Date: Sun, 1 Feb 1998 15:02:54 -0500

The "pulley replacement" issue lead me to the following general

Can imprudent (imprudent = different from manufacturer recommendations
or ?) or frequent periodic maintenance actully increase the risk of

I'm not completely from the school of thought that "If it ain't broke
don't fix it."  However,  I do think that maintenance when not needed
can actually increase the failure probability. (The probablity of
screw-up is greater than zero, the failure probability is fixed-- if
nothing near failure was actually replaced/repaired. . The combined
probability of failure could thus increase after maintenance !

It seems that many recommendations for maintenance are offered as
"experience" and not backed up by statistics proving that a benefit
actually results.  I'm not saying ignore experience-- just quantify it.
 I'd like to know things like component mean-time-to-failure etc or see
that something is really wrong before judging that maintenance was
needed.   Would you replace a 10,000 hour light-bulb every 100 hours to
feel better?

I offer the following (unquantified) observation made my my dad 40 years
ago.  The commercial airplanes he flew had the greatest failure rate of
components just after periodic inspections and preventative maintenance.
 These were performed by those presumably highly skilled in the art and
who did it all the time.( Any others out there with similar
experiences?)  In reality, how practiced are we hams on most tower
maintenance items?  Some are some aren't.   Which are you?    Are you
sure you are truly adding benefit when undertaking "needed"
maintenance-- or are you creating problems?

Vance Net Inc
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