One perennial rite of passage for aircraft owners is what to do about cylinders at overhaul. Whether were talking about top-end work on a mid-time engine, or one we’ll past its published TBO, which cylinders to install can be a major decision. And its not getting any easier. In fact, there’s an element of crisis in the cylinder business. Superior Air Parts was once a major supplier, but is gone from the scene. Continental and ECI have both suffered significant quality issues affecting thousands of cylinders. A recent AD impacts owners of existing Superior cylinders, rendering what was once the cream of the cylinder crop as one-run wonders. One way out of that morass, of course, is to buy a new or factory-rebuilt engine: you’ll get factory jugs. But given Continentals troubles, thats no panacea, either. For those facing top-end work or an overhaul, the choices are more complex. And theyve gotten even harder in recent years given the aforementioned ADs and bulletins. Lycoming owners have it a bit easier: There are no recent ADs against factory cylinders or those supplied by Superior. But anyone with an aftermarket cylinder or flying a Continental engine is probably feeling a little paranoid about all this. After the last three years of ADs, whats going on? Cant anyone make a cylinder anymore? What do engine rebuilders recommend? And what should an owner do when its time to replace one or all of an engines jugs?
Whats The Problem?
The recent spate of ADs against just about every cylinder except Lycoming factory jugs has its roots in the economics of manufacturing. Simply put, its rare for an aircraft piston engine cylinder to be manufactured entirely by the company marketing it. Instead, the work often is farmed out to foundries who cast the cylinder head and barrel and perhaps to another company for heat-treating and machining. Eventually, theyre assembled and packaged in a box labeled Continental, ECI or Lycoming.
Regardless of who does the casting and other work, occasionally a tool will be mis-rigged or a critical process overlooked, resulting in parts not meeting specification. State-of-the-art statistical process control and/or quality inspections are supposed to catch this.
But breakdowns in the QC process don’t affect just cylinders-ask anyone familiar with recalls and ADs on crankshafts from both Lycoming and Continental over the past decade. The bottom line? Stuff happens. And when that stuff involves the potential for cracking, barrel separation and other failure modes, the manufacturers and the FAA get involved.
Most recently, the FAA issued AD 2009-19-07, placing its stamp of approval on a Continental mandatory service bulletin first issued earlier this year. That MSB informed owners of a recall program, including reimbursement, for a bad batch of Continental cylinders prone to cracking.
Over the summer and after a lengthy comment period resulting in 36 public comments-a large number for something as mundane as a cylinder AD-the FAA finalized AD 2009-16-03 against Superior cylinders installed on Continental engines