AOPA Pilot Magazine - January 2016 - 82

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SAVVY MAINTENANCE

overhaul, he is required by regulation to
follow Continental's guidance to the letter,
and that includes complying with SB97-6B.
So if you don't want him to replace those
$5,000 gears and you're happy with your
fuel pump and alternator, just ask him to
log his engine work as a repair instead of
as an overhaul, and then he can do-and
not do-whatever you ask for."
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as supplemented by service bulletins. The
word overhaul implies conformance to
service limits-not necessarily new limits-so if you want new limits you have
to specify a new-limits overhaul. A newlimits overhaul is essentially the same as
rebuilt, except that it doesn't have to be
performed by the original manufacturer
and doesn't receive a new serial number
or a zero-time logbook.
Repaired means inspected and repaired
as necessary (IRAN) to restore the inoperative component to proper working
condition. This term implies nothing
about fits and limits, because there is no
requirement to measure anything when

The "O-word" is one of the most expensive and overused
words in aviation maintenance.
the bad component with a new one or a
rebuilt one, or have the defective component overhauled or repaired.
These four words-new, rebuilt, overhauled, and repaired-are terms that have
distinct, specific meanings in the context
of aircraft maintenance. Those meanings
are defined in the federal aviation regulations. It's crucial for owners to understand
precisely what they mean and how they
differ.
New means never used. Dimensionally,
a new component meets new fits and limits (obviously).
Rebuilt means a previously used component that has been overhauled to new
fits and limits (possibly using approved
oversize or undersize parts) by the original manufacturer. For example, only the
Continental factory in Mobile, Alabama,
can "rebuild" a Continental engine,
although any A&P mechanic or engine
shop can "overhaul" one. When the factory rebuilds a component, it receives a
new data plate with a new serial number;
if it's an engine it receives a new zero-time
logbook with no record of previous operating hours or history.
Overhauled means disassembled,
cleaned, inspected, repaired as necessary,
reassembled, and tested in accordance
with the manufacturer's approved technical data-normally the overhaul manual

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82 | AOPA PILOT January 2016

performing a repair. One could, for example, remove a cylinder, replace a burned
exhaust valve and guide, and then reinstall
the cylinder without measuring anything,
and call it a repair.
A repair differs from an overhaul primarily in that there's no obligation to
follow the fits, limits, mandatory parts
replacements, and other procedures in
the manufacturer's overhaul manual. The
FAA's late, great Bill O'Brien-who long
served as the agency's top maintenance
guru-used to drive this point home to
mechanics who attended his IA renewal
seminars by using this catchphrase: "If you
used a micrometer, then it's an overhaul; if
you didn't, then it's a repair."
When an owner asks a mechanic to
overhaul something instead of repair it, he
ties the mechanic's hands. The mechanic
is no longer able to use discretion as to
which parts are worn out and need to be
replaced, and which parts look fine and
can be retained. He must slavishly replace
100 percent of the parts on the manufacturer's mandatory replacement list (even
if they appear to be in perfect condition),
and he must measure all the other parts
and replace them if they fail to meet the
manufacturer's service limits.
The words overhauled and rebuilt"are
defined in FAR 43.2 and have specific regulatory meanings. If a mechanic documents
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Table of Contents for the Digital Edition of AOPA Pilot Magazine - January 2016
