The Zero-Time Myth

Only the factories have the legal right to declare an engine "zero time." As Coy Jacob explained recently in Aviation Consumer, that doesn't mean all new parts. A zero-time engine can contain used parts - perhaps many used parts of unknown service history. Here's what you're really getting for your flying dollar.


What’s in a name? Or a label? When it comes toaircraft engines, a simple label — or, more properly, a logbook notation — cancarry an impressive cache that, in reality, may not mean what you think. A casein point is the value a buyer or owner puts on a "zero-time" engine asopposed to a freshly overhauled powerplant from a field shop. Hands down, thezero-time is thought to be a better engine, since it has all new parts. Except,of course, it might not have all new parts. In some cases, a field overhaulcould have more new parts than a zero-time factory engine.

Obviously, excluding test-stand time, new recently manufactured engines arefairly and properly termed zero-time. All the parts will be factory new.However, the FAA also allows the original equipment manufacturers (OEMs) tolabel their rebuilt engines "zero time," a minor sleight of the penthat has some field overhaul shops fuming. We don’t blame them, frankly. As faras engine longevity, "zero time" versus "stated total time"may make little difference in the outcome. But if you think you’re gettingsomething you’re not, the term is misleading at best.

OEMs Only, Please


Engine Overhaul
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No one but the OEMs have the official, FAA-blessed right to term any enginezero time, even if the scope of work done on the engine by a field shop isexactly the same as the factory’s rebuild process. Actually, even the OEM’s ownoverhaul shops can’t call their overhauled engines "zero time."Lycoming, of course, offers factory overhauls and new engines, while Continentalsells new and remanufactured engines only. A terminology note here: FAA regsdon’t recognize the term "remanufactured" but use the term"rebuilt." In this article, we have used the termsinterchangeably. 

In Canada, the rules are a little different. The Canadian AviationRegulations don’t have an equivalent to our FAR 91.421, which allows "zerotime" to be recorded for a factory rebuilt engine. So in Canada, the actualtime or the term of prior duty time is considered "total timeunknown." Only a new engine is zero time.

Even though the factory’s actual remanufacturing/rebuilding process may befunctionally identical to what most competent engine shops offer on new limitsoverhauled engines, buyers seem enamored with the idea that a zero-time enginefrom the factory contains all new parts. That’s simply not the case.

For years, field shops have complained about this practice — an"exalted privilege granted from on-high" — as one engine shop ownerputs it. One industry activist, Bill Schmidt of Cincinnati-based SignatureEngines, believes that zero-timing is paramount to false advertising and hasofficially petitioned the FAA to change the rules. He even has his own Web siteto carry the cause forward, site includes Schmidt’s petition to the FAA.

How It Works

From the FAA’s point of view, the OEMs have access to the original productiondrawings, thus they can theoretically attest that each engine component conformsto new specs during the rebuilding process, whether it’s a new part or one with2000 hours of flight time. In other words, your "zero-time" crankshaftcan legally be undersize due to wear but still treated like new because thefactory allows it.

In practice, how important are these production drawings? Not very, in ourestimation. Except under the most unusual of circumstances, everything anycompetent shop needs to know about how to overhaul the engine is contained inthe OEM Service and Overhaul Manuals. Having the production drawings is a nicetechnicality but unconvincing as basis for building a better engine. In fact,we’re told by industry insiders that the drawings are rarely used anyway, sincethe principal specifications are in the overhaul manuals, for all to see.Drawings are, however, critical when building new engine components fromscratch.

Most reputable engine shops not only believe the term "zero time"means nothing, but some even consider it blatant false advertising. Jimmy Broad,of Sebring, Florida-based JB Aircraft Engines Services, says that, while theOEMs may not admit to it, it’s entirely possible for a factory zero-time rebuiltengine to contain parts having more total time than the engine it’s replacing.

Engine modifier Terry Capehart of High Performance Engines Ltd. in Mena,Arkansas and Zephyr Engine’s Charlie Mellot in Zephyrhills, Florida, say thereare instances in which internal components involved in sudden stoppages oraccidents have found their way into zero-time engines. (The same is true offield overhauls, by the way.)

At present, there’s no legal obligation for anyone turning an engine in for acore charge to inform the factory of such abuse. The typical independent shopmay actually have a better handle on the past history of the engines they offerthan does the factory, which receives cores by the pallet load. Of course, thefactories do inspect the parts for wear and damage before reusing them, just asoverhaul shops do.

Just why did the FAA allow this practice to get started? Probably because,until about the late 1980s when new airplane production was less anemic than itis now, the engine makers only built new engines. They left overhauls to fieldshops. When the new engine business declined, the factories went after theoverhaul business with two distinct advantages: the economy of scale conferredby volume and the cache of holding the engines’ birthright. In other words, withminimal FAA oversight, the factories declared the standard and passed it down tothe field shops doing overhauls.

When the factories began overhauling and remanufacturing, exchange engineswere returned to the factory, disassembled and parts inspected, sorted and putinto bins of identical parts to be reassembled later. Similar parts were thensorted as being within OEM new specs, serviceable, or outright junk, which wasdiscarded. Because any future re-assembly into engines could actually besomewhat of a mix of used and new parts, the end result would bear littleresemblance to any specific run-out engine from whence the parts came.

Major components such as crankshafts, cases, gears and so on are typicallyre-used if they meet specs. However, the OEMs claim they can’t keep track ofevery used component’s total time in service, nor do they typically make anyeffort to do so. In fact, as exchange cores are passed through the rebuildingprocess, individual engine components are typically not kept together as afunctioning parts group.

Volume, Numbers

From a volume/manufacturing standpoint, this makes sense. Keeping a group ofnon-serial numbered parts together can be a logistical nightmare and, even ifyou could do it, how would you log the time for each component and what meaningwould that have? The part total time designation loses its value unless all thecomponents are kept together as one functioning engine, sans those componentsreplaced by new parts.

This, too, is logical, given the sloppy state of paperwork that passes forlogging these days. Our audits of engine and airframe logbooks turn up all kindsor errors, great and small. It’s not uncommon to see gaps of thousands of hoursin an aircraft’s history.

That said, if you opt to have your engine overhauled by Lycoming and youspecifically decline an exchange, you’ll get your own serviceable core partsback, plus any new parts installed during the overhaul. If you opt for anexchange overhaul from Lycoming, the engine could be composed of used core partsof widely varying times.

Continental doesn’t overhaul, per se. It sells new and remanufactured enginesor, in FAA parlance, rebuilt. As we’ve reported, Continental bought MattituckAviation Corp., a respected overhaul shop, in 1999. Mattituck does selloverhauls and, in that sense, is no different than any other field shop.

What the Factories Say


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For the OEM view, we contacted Continental and Lycoming, both of whomobviously have a different take on the zero-time issue. For its part, Lycomingsays the company does enjoy advantages over overhaul shops. Lycoming’s VP andChief Engineer Rick Moffit argues that, in general aviation recips, the notionof time-limited parts doesn’t exist, although manufacturers do publishrecommended TBOs which are mandatory only for for-hire operations.

Lycoming doesn’t serialize the majority of its parts, thus there’s nomechanism in place to keep track of the duty times of internal parts. This meansthat while the "parts bin" argument may have had some merit ininfluencing the FAA some years ago, the need to track duty time of reinstalledcomponents is neither necessary nor perhaps meaningful.

Although it wasn’t mentioned specifically in our conversations, we’re surethe lawyers have some stake in the "zero-time" argument as well,especially as it relates to the factories’ publishing minimum/maximum timespecifications for certain parts. Were they to publish specific accepted minimumtimes for components, field shops might then be able to call their engines"zero time." But this might also increase the company’s liabilityexposure. In effect, any part that failed before the replacement time could beconstrued as being officially okayed by the factory.

Teledyne Continental’s chief engineer John Barton and Jay Wickham, whooversees the Mattituck operation, support the view that having productiondrawings gives the factories a meaningful advantage. And while it’s true thatthe drawing themselves aren’t always on the factory floor, TCM says the drawingrequirements are increasingly controlled by a computer system called CAPPS forcomputer aided process planning system.

This system makes dimensions and requirements readily available in thefactory to a level of detail not included in overhaul manuals. Further, theCAPPS system contains the latest drawing revisions, which overhaul manuals maynot.

Indeed, say Wickham and Barton, it’s not unusual to find factory overhaulmanuals not in evidence at an overhaul shop, a way of work that may be effectivefor shops but would prohibit Continental from factory authorizing such a shop.Of more material import, says TCM, is that parts used in zero-time engines aresubjected to the rigorous requirements of factory new components. For example,reworked crankshafts are examined and undergo the same 40-hour nitriding processthat all factory new crankshafts get. If field overhaul shops provide thisservice, says TCM, it’s not likely to be the same process the factory uses.

TCM says that during its rebuilding process, it routinely destroys allcylinders and many other components that might otherwise find their way intooverhauled engines, legally or not. Many rejected parts may in fact meet servicelimits overhaul requirements but not new requirements. Continental says one ofits rebuilt engines is likely to contain more new parts than a field overhaul.

The confusion — and to a degree, the deception, is there for the taking byall parties — over the "zero-time" issue. TCM’s Wickham notes thatmany facilities that compete with Continental use intentional "factorydisparagement" to create favorable buyer impression of their products.Since the factory doesn’t sell direct, it relies on distributors and shops withpotentially conflicting sales interests to sell its products, thus a detailedunderstanding of what goes into a zero-time engine is not necessarily conveyedto the potential buyer.

The PMA Market

Gary Garvins, CEO of Engine Components, Inc., a major PMA house, sees bothsides of the argument. He agrees with the Lycoming line of reasoning but he alsoagrees with shop owners who believe the zero-time claim is misleading at best,false advertising at worst. But, says Garvins, the zero-time privilege for thefactories was set in stone four decades ago and it would take an act of Congressto change it. (One engine shop owner told us, "if the FAA could drop thezero-time issue without un uproar, it would.") What Garvins and engineshops object to is that OEMs are essentially allowed to "throw away thelogbooks" on used but serviceable components and then to use the zero-timeclaim in advertising, which gives them a distinct advantage in the minds ofbuyers.

Tim Archer, who is senior vice president for Superior Air Parts, another bigPMA supplier, says there are more issues at stake than just the zero-time claim.Archer, by the way, worked for Continental for years, so he has seen theargument from both sides of the fence. He says the real issue shouldn’t be thelogbook verbiage but what it implies. In other words, do you want to know thehistory of all the parts used in building up your rebuilt/overhauled engine ornot?

The OEM’s would have us believe that they’re the only ones who can accuratelydetermine if the used parts should be reused and that they have uniqueinspection ability. But is that true in the real world? Archer says no. He saysthere are many quality engine shops fully capable of assembling engines equal toor better than anything turned out by the factories. In fact, says Archer, the"one man, one engine" build-up method used by field shops has theadvantage of allowing closer inspection and checking of each phase of theoverhaul.

Zephyr’s Mellot argues simply for more truth in advertising: "Mysuggestion would be to allow the factory to use the term ‘zero-time sinceremanufacture’ due to the fact that they’re the only ones with the proprietarymanufacturing drawings. After all, these are their drawings and I can’t blamethem for not wanting to release them."

This would alert the buyer to the fact that the engine is not zero time sincenew but contains used parts. To some buyers, it’s important to know this. Ourview is that many buyers don’t make the distinction.

What It All Means

Even though engine shops chaff at the advantage enjoyed by the OEMs and BillSchmidt is trying to get his Zero-Time Coalition off the ground, don’t look foranything to change soon. In researching this article, we sensed that this issueis a hot potato that the OEMs and the FAA would very much like to ignore.

The engine factories, like the airframers, are struggling to retainprofitability and we doubt the FAA is going to propose rulemaking to make thejob any harder. To be fair, the engine factories do retain the mother lode ofdetailed information on the engines they build and are often the only source ofinformation critical to overhauling an engine correctly. Both Lycoming andContinental rightly point out that their factory drawings contain informationnot found in overhaul manuals. On the other hand, the best field shops have beendoing nothing but overhauls for decades and we know from experience that theyknow tricks the factories don’t, because building an engine is not the same asoverhauling one.

It is true that a zero-time engine is different from an overhauled engine,but only by a degree determined by how many new parts it might have and, as TCMsays, additional inspection processes. Both engines will have used orreconditioned parts. The cold reality is that, in terms of durability, safetyand value, there’s little difference between a zero-time overhaul from thefactory and an overhaul from a reputable field shop. To us, the more criticalfactor is how the builder supports its work with warranty performance.

Given the product recalls from the factories — mostly recently on Lycomingcrankshafts — we don’t think either OEM is in a position to claim the highground on superior quality control.

The bottom line? When you see a logbook with a claim of a zero-time engine,know that, unless it’s a factory-new engine, it contains used parts. Perhapsmany used parts of unknown service history.

This isn’t a bad thing; nor does it mean the engine is blemished. But if youbuy an engine labeled "zero time" and expect to get all new parts, youwon’t. If all new parts are important, buy a new engine.