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Airtime 2014  002We are always on the look out for interesting stories from the aviation world and we came across one article, "The Ten biggest lies in aviation", which makes a lot of sense.  In particular we thought "lie" 10 was interesting.

"A factory overhaul is better than a field (maintenance facility) overhaul, because only the factory offers a true "zero-timed" engine" While it's true that a factory rebuilt engine comes with a zero-time logbook while a field overhauled engine does not, it's not for the reason you may think.

When you have your engine overhauled by Airtime, or whomever, that engine retains most of its original parts, as well as its serial number, data plate, and engine logbook or other maintenance records. The overhauled engine you get back is legally the same engine you sent in, all cleaned up with lots of new parts.

On the other hand, when TCM or Lycoming receives a runout core from a customer, that engine loses its identity. The data plate is removed and destroyed. So are the logbooks. The case halves are cleaned up, inspected, and added to a big pile of reusable case halves. The crankshaft is cleaned up, inspected, and added to a big stack of reusable cranks. The same is true of camshafts, rods, accessory gears, and so forth. Those reusable parts become "anonymous" because they're no longer associated with any particular engine serial number.

Now, when TCM or Lycoming builds up a factory rebuilt engine (colloquially but incorrectly referred to as a "factory reman"), it pulls some "anonymous" case halves from one pile, an "anonymous" crankshaft from another pile, and so forth. When the engine is completely assembled, it gets a new data plate, a new serial number, and a new logbook.

The logbook starts out at zero time-in-service. Why zero? Because there's no other reasonable figure to put in the logbook. The case halves are certainly not zero-time, but there's no record of how much time they've accrued. The crankshaft may not be new, but there's no record of how much time is on the crank, either. And so on.

In short, the "zero-time" logbook that comes with a factory rebuilt engine in no way implies that the engine is "newer" or "better" than a field overhaul. All it implies is that the reused components in the engine are of unknown heritage...nobody knows how long they were in service prior to the time then were cleaned up, inspected, and reused in your engine!


This and the other 9 top ten lies in aviation from the article of the same name can be found by clicking here


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