The Terminology and Standards of Aircraft Engine Overhaul – Part 3

As a final installment in our series of posts intended to demystify the aircraft engine overhaul process, we at Covington Aircraft want to detail the differences between using new and overhauled parts in an engine overhaul, so that you can make the best and most informed decision possible when TBO time comes around again.

When you’re looking to get an engine overhaul, a key point to remember is that the FAA does not require that all parts need to be replaced with brand new OEM equipment. While it is an accepted practice to replace parts such as pistons, rings, bushings, seals and gaskets, it’s also an accepted practice to reuse internal steel parts like connecting rods, the crankshaft, pushrods, gears and drive shafts, among others.

Testing and replacement


Even if they are reused, all non-new parts are carefully inspected and checked for cracks or defects via non-destructive testing techniques like Magnaflux and dye-penetrant tests. If a part fails to meet specified dimensional limits—either new limits or service limits, depending on the type of overhaul you’ve requested—it will be immediately rejected and replaced, regardless of the owner’s preference on the matter. The downside of this replacement is that some components come in matched sets, which means that a damaged single Planet gear may require the replacement of all Planet gears.

To overhaul or not to overhaul your parts?

When getting an engine overhaul, it can be difficult to decide if you should overhaul your existing cylinders or just replace them with new ones. New cylinders, if available, cost more than overhauling the cylinders you’ve already got. If your existing cylinders don’t have much wear, then it’s probably perfectly acceptable to get them overhauled and reinstalled. Remember that an overhauled cylinder still gets a new cylinder barrel choke and cylinder barrel honed finish, and the guides and seats are refurbished or replaced.

If you’re interested in further information on aircraft engine overhauls for turbine or radial engines, please let us know. We welcome questions and e-mails, and always strive to provide the best service possible to all our customers.

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