ECI Cylinder AD: The More You Look, the Worse It Is
Hereís my definition of a bad day: You overhauled your Baronís IO-520s† a couple of years ago using cylinders from ECI and now the FAA would like you to remove those jugs and replace them with something else. Round it off and call that about $25,000.
Thatís the basic gist of a proposed airworthiness directive the FAA announced two weeks ago and about which weíve been reporting regularly. The AD targets about 30,000 ECI cylinders of various vintages for two kinds of cracking: a failure in the shrink band that holds the head to the cylinder barrel via an interference fit and cracking in the dome of the head. Both flaws can result in catastrophic cylinder failure, but †not necessarily complete engine failure.
On this much, the FAA and ECI agree, but they see eye-to-eye on little else. They donít agree on the number of actual failures in the fieldóthe FAA says more than 30, ECI says it can confirm 19. Nor do they agree on the failure mechanism. In the AD documentation, the FAA says it doesnít know what the failure modes are, just the results, while ECI insists that the head/barrel separations were caused by overheating due to pilot engine mismanagement. Maddeningly, the governmentís own NPRM process precludes the FAA from supplying specific information on its methodology or the underpinnings of its conclusion to demand removal of these cylinders. The AD docket gives some information, of course, but ECI says it has a lot of questions the FAA isnít answering.†
In my view, no reasonable person could look at the available dataóa combination of Service Difficulty Report analysis, field reports and in-house manufacturing historyóand feel confident of having an accurate picture of reality. In short, the data is just too sketchy. It may be biased toward classifying failures that arenít head/barrel separations or it may very well miss many that are. I'm not sure you can tell which is which from reviewing the data.
Taking the broader view from this too vague compilation of dodgy numbers and unsupported theories, ECI concedes this: When compared to Continental Motors OEM cylinders, its incidence of head/barrel separation is much higher, although just how much higher we donít know. They donít either because they donít have accurate numbers for the Continental OEM cylinder population. ECI says it has about 25 percent of the cylinder market and during the period 2002 to 2012, ECI insists it had 19 verified head/barrel separations compared to 24 for Continental on the same 520/550 cylinders. The raw data ECI provided us showed 36 failures, but the company says many of those were unverified or improperly classified. † †
Just to grasp at some kind of solid foundation in a field of numbers that just donít add up, letís accept ECIís 19 failures. As these things go, thatís comparable to the Continental record, except for one thing: it applies to a much smaller population of cylinders, so the rate of failure is at least twice as high, but could be four or more times as high, depending on whether ECIís estimate of its cylinder market share is accurate. On a rough per engine basis, the 30,000 ECI cylinders under the gun represent 5000 engines, meaning that with 19 incidents, the per engine rate is one failure per 263 engines. For Continental engines, the rate is much lower, perhaps as much as four or more times lower.
Isnít that damning for ECI? It certainly doesnít look good. Thereís got to be some explanation for ECIís higher failure rate. And there is, but first, letís put things in perspective. Worst case, at least from the data we have and with the caveats Iíve described, the percentage of ECI cylinders with head/head barrel separations is 0.12 if you accept the FAA data and about half that if you take ECIís data. Moreover, ECI's data shows a declining incidence of head/barrel separations, with none at all during the past two years. Its statistical analysis suggests the separations are in decline in the target cylinder population.†
While itís true that these rates and percentages are worse than for Continental cylinders, we are still talking about very small risks indeed. Could it be that there have actually been many more ECI head/barrel separations than have been reported? Maybe, but if thatís so, why havenít any of the six engine shops I canvassed two weeks ago seen them? It seems reasonable that if thereís a breaking wave of heads flying off of barrels, at least some of the shops would know about them. They donít seem to. Nor have we heard from any readers with direct experience following the ECI story.
†As I†reported two weeks ago, what some of the shops have seen is what I call pedestrian crackingócracks around fuel injector bosses, spark plug holes and the like. Some shops think ECI cylinders are more susceptible to this and have stopped recommending them, but thatís an entirely different consideration that has nothing to do with head/barrel separations.
So against this backdrop of uncertain data and a small risk, the FAA proposes the potential of an $83.3 million AD to selectively remove these cylinders from service, the cost to be borne entirely by owners. Given the weakness of the data and the small numbers, this is obviously hitting a small nail with an exceedingly large hammer. Absent better data from the FAA, I just donít see how this AD is justified.
But thatís not to say nothing should be done. ECI doesnít challenge the fact that Continental OEM cylinders have a much lower rate of head/barrel separation. Their explanation for this is that their cylinders live in a different market segment thatís heavy on older or aftermarket applications in which pilots donít have sophisticated engine monitoring and are thus more likely to mismanage engines and thermally stress their cylinders, which ECI says is the failure cause, not manufacturing or quality issues. When I visited ECI in San Antonio last week, they showed me data that clearly showed how cylinder mating threads are stressed by over temping, with the load curve heading straight up above 450 degrees or so.
But Iím not quite ready to buy this argument, frankly. Plenty of Continental OEM cylinders go on older Bonanzas and Cessnas and thereís no reason to believe the pilots of those airplanes are any more or less hamfisted with the mixture knob than are ECI cylinder buyers. And ECI doesnít have the electronic data from any cylinder failure events to correlate the theory in the real world.
Bottom line, ECI cylinders fail at a higher rate, but not so high as to represent meaningful additional risk worthy of the FAAís massive AD. †The risk here is too small for the FAA to wade in and dent owners with this kind of overbroad, expensive AD. While the FAA has a duty to protect the public safety, it should do so reasonably and with cost in mind. Small or marginal risksóand this appears to be in that categoryóshould be left up to aircraft owners to judge and mitigate. In my view, a non-mandatory service bulletin that summarizes the data and advises †owners of the failure pattern and rate and how to inspect cylinders for potential cracks seems the fair way to approach this. Owners can then make their own risk/cost assessments, which is what owning an airplane is all about anyway. Then watch the situation for a couple of years and revisit as necessary. Otherwise, the AD ought to be dropped for now.