Engine Overhaul
Terminology and Standards
TBO time draws near and you need to decide on a course of action. You call
around, talk to your maintenance facility, and find that you are totally
confused because you don't understand or know the definitions of many of the
terms used by the people that you have been talking to.
New limits, Service limits, Remanufactured, Rebuilt, New, Used, Overhauled,
Like new, OEM, Aftermarket, what does it all mean?
Lets look at and define the terms that are approved to be used by the FAA.
A NEW ENGINE is an engine that has been manufactured from all new
parts and tested by an FAA approved manufacturer. The engine will have no
operating history except for test cell time when received. No FAA approved
manufacturer can approve another entity to manufacture or assemble a NEW
ENGINE.
NEW LIMITS are the FAA approved fits and tolerances that a new engine
is manufactured to. This may be accomplished using standard or approved
undersized and oversized tolerances.
SERVICE LIMITS are the FAA approved allowable wear fits and
tolerances that a new limit part may deteriorate to and still be a useable
component. This may also be accomplished using standard and approved undersized
and oversized tolerances.
An OVERHAULED ENGINE is an engine which has been disassembled,
cleaned, inspected, repaired as necessary and tested using FAA approved
procedures. The engine may be OVERHAULED to NEW LIMITS or SERVICE
LIMITS and still be considered a FAA approved OVERHAUL. The engine's
previous operating history is maintained and it is returned to you with zero
time since major OVERHAUL and a total time since new that is the same as
before the OVERHAUL.
A REBUILT ENGINE is an engine that has been OVERHAULED using
new and used parts to NEW LIMITS by the manufacturer or an entity
approved by the manufacturer. At the current time neither Teledyne Continental
or Textron Lycoming approve any other entity to REBUILD engines for
them. The engine's previous operating history is eradicated and it comes to you
with zero hours total time in service, even though the engine may have had used
components installed that have many hours of previous operating history .
Textron Lycoming uses the term Remanufactured in their advertising and
commercial media to describe their factory rebuilt engines. Although this term
has no official definition in the eyes of the FAA, when used by the Textron
Lycoming and only when used by Textron Lycoming the term Remanufactured should
be considered the same as the term REBUILT.
When an engine is OVERHAULED or REBUILT the new parts that are
used during the repair process can come from a variety of sources. An O.E.M.
part is a new part that is manufactured by the original engine manufacturer to
stringent F.A.A. standards. An AFTERMARKET part is a new part that is
manufactured by someone other than the original engine manufacturer that meets
or exceeds the same stringent F.A.A. guidelines as a new O.E.M. part.
Any other terms used to describe the work performed during a engine overhaul
are defined by the person or entity using them. They have no official meaning
and often times are very misleading. Terms like "overhauled to factory
specs or tolerances", "rebuilt equivalent", "overhauled to
like new condition" and "remanufactured to factory fits and
limits" and any other terminology that isn't defined above needs to be
investigated as to what those terms actually mean. You will probably find that
advertisements and log entries that use undefined terminology are not really
delivering what you think you are getting. There are specific requirements by
the FAA for the use of the terms OVERHAULED and REBUILT in an
engine's maintenance records. If these requirements are not met it is illegal
to use the terms. Any terms other than those listed have no meaning in the eyes
of the FAA and should not be accepted by you in your engine log books.
Now that we understand all the terms, let's put it all in a nut shell. Only
the manufacturer can currently produce a new or rebuilt engine. Both new and rebuilt
engines are made to new limits. A new engine will have all new O.E.M. parts. A
rebuilt engine can be produced using a combination of used and new O.E.M.
parts. An overhauled engine can be done to new limits or to service limits or a
combination of the two using used parts and new O.E.M or new aftermarket parts.
An overhauled engine comes to you with it's previous operating history intact
and zero hours since major overhaul. A new or rebuilt engine comes to you with
no previous operating history and zero hours time in service, even though, in
the case of a rebuilt engine, some of the parts used may have a previous
operating history.
Understanding these terms and the regulations that apply to them, may make
the decisions that you have to make, at TBO time, a little easier.
Send your questions, to Mahlon at mahlon@mattituck.com
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