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.
by Coy Jacob
This article appears in the March, 2002 edition of Aviation Consumer, and is reprinted here by permission.

What's in a name? Or a label? When it comes to aircraft engines, a simple label -- or, more properly, a logbook notation -- can carry an impressive cache that, in reality, may not mean what you think. A case in point is the value a buyer or owner puts on a "zero-time" engine as opposed to a freshly overhauled powerplant from a field shop. Hands down, the zero-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 overhaul could have more new parts than a zero-time factory engine.

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

OEMs Only, Please

No one but the OEMs have the official, FAA-blessed right to term any engine zero time, even if the scope of work done on the engine by a field shop is exactly the same as the factory's rebuild process. Actually, even the OEM's own overhaul shops can't call their overhauled engines "zero time." Lycoming, of course, offers factory overhauls and new engines, while Continental sells new and remanufactured engines only. A terminology note here: FAA regs don't recognize the term "remanufactured" but use the term "rebuilt." In this article, we have used the terms interchangeably.

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

Even though the factory's actual remanufacturing/rebuilding process may be functionally identical to what most competent engine shops offer on new limits overhauled engines, buyers seem enamored with the idea that a zero-time engine from 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 owner puts it. One industry activist, Bill Schmidt of Cincinnati-based Signature Engines, believes that zero-timing is paramount to false advertising and has officially petitioned the FAA to change the rules. He even has his own Web site to carry the cause forward, The 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 production drawings, thus they can theoretically attest that each engine component conforms to new specs during the rebuilding process, whether it's a new part or one with 2000 hours of flight time. In other words, your "zero-time" crankshaft can legally be undersize due to wear but still treated like new because the factory allows it.

In practice, how important are these production drawings? Not very, in our estimation. Except under the most unusual of circumstances, everything any competent shop needs to know about how to overhaul the engine is contained in the OEM Service and Overhaul Manuals. Having the production drawings is a nice technicality but unconvincing as basis for building a better engine. In fact, we're told by industry insiders that the drawings are rarely used anyway, since the principal specifications are in the overhaul manuals, for all to see. Drawings are, however, critical when building new engine components from scratch.

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 the OEMs may not admit to it, it's entirely possible for a factory zero-time rebuilt engine 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 there are instances in which internal components involved in sudden stoppages or accidents have found their way into zero-time engines. (The same is true of field overhauls, by the way.)

At present, there's no legal obligation for anyone turning an engine in for a core charge to inform the factory of such abuse. The typical independent shop may actually have a better handle on the past history of the engines they offer than does the factory, which receives cores by the pallet load. Of course, the factories do inspect the parts for wear and damage before reusing them, just as overhaul 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 it is now, the engine makers only built new engines. They left overhauls to field shops. When the new engine business declined, the factories went after the overhaul business with two distinct advantages: the economy of scale conferred by volume and the cache of holding the engines' birthright. In other words, with minimal FAA oversight, the factories declared the standard and passed it down to the field shops doing overhauls.

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

Major components such as crankshafts, cases, gears and so on are typically re-used if they meet specs. However, the OEMs claim they can't keep track of every used component's total time in service, nor do they typically make any effort to do so. In fact, as exchange cores are passed through the rebuilding process, individual engine components are typically not kept together as a functioning parts group.

Volume, Numbers

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

This, too, is logical, given the sloppy state of paperwork that passes for logging these days. Our audits of engine and airframe logbooks turn up all kinds or errors, great and small. It's not uncommon to see gaps of thousands of hours in an aircraft's history.

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

Continental doesn't overhaul, per se. It sells new and remanufactured engines or, in FAA parlance, rebuilt. As we've reported, Continental bought Mattituck Aviation Corp., a respected overhaul shop, in 1999. Mattituck does sell overhauls and, in that sense, is no different than any other field shop.

What the Factories Say

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

Lycoming doesn't serialize the majority of its parts, thus there's no mechanism in place to keep track of the duty times of internal parts. This means that while the "parts bin" argument may have had some merit in influencing the FAA some years ago, the need to track duty time of reinstalled components is neither necessary nor perhaps meaningful.

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

Teledyne Continental's chief engineer John Barton and Jay Wickham, who oversees the Mattituck operation, support the view that having production drawings gives the factories a meaningful advantage. And while it's true that the drawing themselves aren't always on the factory floor, TCM says the drawing requirements are increasingly controlled by a computer system called CAPPS for computer aided process planning system.

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

Indeed, say Wickham and Barton, it's not unusual to find factory overhaul manuals not in evidence at an overhaul shop, a way of work that may be effective for 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 are subjected to the rigorous requirements of factory new components. For example, reworked crankshafts are examined and undergo the same 40-hour nitriding process that all factory new crankshafts get. If field overhaul shops provide this service, says TCM, it's not likely to be the same process the factory uses.

TCM says that during its rebuilding process, it routinely destroys all cylinders and many other components that might otherwise find their way into overhauled engines, legally or not. Many rejected parts may in fact meet service limits overhaul requirements but not new requirements. Continental says one of its 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 by all parties -- over the "zero-time" issue. TCM's Wickham notes that many facilities that compete with Continental use intentional "factory disparagement" to create favorable buyer impression of their products. Since the factory doesn't sell direct, it relies on distributors and shops with potentially conflicting sales interests to sell its products, thus a detailed understanding of what goes into a zero-time engine is not necessarily conveyed to the potential buyer.

The PMA Market

Gary Garvins, CEO of Engine Components, Inc., a major PMA house, sees both sides of the argument. He agrees with the Lycoming line of reasoning but he also agrees 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 the factories was set in stone four decades ago and it would take an act of Congress to change it. (One engine shop owner told us, "if the FAA could drop the zero-time issue without un uproar, it would.") What Garvins and engine shops object to is that OEMs are essentially allowed to "throw away the logbooks" on used but serviceable components and then to use the zero-time claim in advertising, which gives them a distinct advantage in the minds of buyers.

Tim Archer, who is senior vice president for Superior Air Parts, another big PMA 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 the argument from both sides of the fence. He says the real issue shouldn't be the logbook verbiage but what it implies. In other words, do you want to know the history of all the parts used in building up your rebuilt/overhauled engine or not?

The OEM's would have us believe that they're the only ones who can accurately determine if the used parts should be reused and that they have unique inspection ability. But is that true in the real world? Archer says no. He says there are many quality engine shops fully capable of assembling engines equal to or 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 the advantage of allowing closer inspection and checking of each phase of the overhaul.

Zephyr's Mellot argues simply for more truth in advertising: "My suggestion would be to allow the factory to use the term 'zero-time since remanufacture' due to the fact that they're the only ones with the proprietary manufacturing drawings. After all, these are their drawings and I can't blame them for not wanting to release them."

This would alert the buyer to the fact that the engine is not zero time since new but contains used parts. To some buyers, it's important to know this. Our view 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 Bill Schmidt is trying to get his Zero-Time Coalition off the ground, don't look for anything to change soon. In researching this article, we sensed that this issue is a hot potato that the OEMs and the FAA would very much like to ignore.

The engine factories, like the airframers, are struggling to retain profitability and we doubt the FAA is going to propose rulemaking to make the job any harder. To be fair, the engine factories do retain the mother lode of detailed information on the engines they build and are often the only source of information critical to overhauling an engine correctly. Both Lycoming and Continental rightly point out that their factory drawings contain information not found in overhaul manuals. On the other hand, the best field shops have been doing nothing but overhauls for decades and we know from experience that they know tricks the factories don't, because building an engine is not the same as overhauling 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 TCM says, additional inspection processes. Both engines will have used or reconditioned parts. The cold reality is that, in terms of durability, safety and value, there's little difference between a zero-time overhaul from the factory and an overhaul from a reputable field shop. To us, the more critical factor is how the builder supports its work with warranty performance.

Given the product recalls from the factories -- mostly recently on Lycoming crankshafts -- we don't think either OEM is in a position to claim the high ground 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. Perhaps many used parts of unknown service history.

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


About the author...

Coy Jacob is a contributing editor to Aviation Consumer. He operates the Mod Squad, formerly the Mooney Mart, in Venice, Florida.



Published: 03/14/02