Cessna Cardinal, with almost 450
hours passed TBO and 20 years since
it was overhauled, may have reached
retirement age.
Tom, I've got bad news for you," Brian says when I answer the phone.
The phone call isn't a surprise. I've expected the call every time my airplane was in the hands of a mechanic during the last year or so, but it isn't welcome.
The Lycoming IO-360 in my 1976 Cardinal RG was overhauled in 1989. Since that time I've logged 2,440 hours on the engine. Lycoming recommends a TBO (time between overhauls) of 2,000 hours or 12 years, so the engine has performed much better than expected. The TBO is advisory, not mandatory (unless the airplane is used in revenue service under Part 135 or 121), so as long as the engine is performing as it should and the oil analyses and oil filter inspections aren't showing unusual levels of metal, there's no reason not to let the engine soldier on. The oil analyses have been very positive. In fact, the most recent one from Blackstone Labs concluded: "Nice report at 2,429 hours SMOH."
On a recent flight to rendezvous with Jon, a friend I am meeting for lunch at Schenectady (KSCH) Airport in New York, when I do the run-up before takeoff and switch to the left magneto, the engine shakes and runs very roughly. The J.P. Instruments engine analyzer indicates the No. 2 cylinder isn't happy. Back on both it runs smoothly. I lean the mixture even more aggressively and run up the power to attempt to burn off any carbon buildup on a spark plug. It takes awhile, but eventually the engine runs smoothly and the mag drops are even and well within parameters. I assume the problem is carbon buildup and leaning the mixture has fixed the problem. The short flight to Schenectady is uneventful.
Then, after lunch, when I taxi out to fly home, the mag check again raises flags. This time it's the No. 4 cylinder on the JPI that isn't happy. I tell the controller I need to taxi back to the FBO. Jon, who is getting ready to depart, hears my radio call and asks the controller if he can contact me. "Tom, you want me to wait?" he asks.
"Yeah, Jon, maybe you better. I may have to leave the airplane here and, if so, I'll need you to fly me back to Columbia County."
I taxi back to the FBO where Jon is waiting. Before I shut down the engine, I lean it and again do the mag checks. This time the check is again fine. Standing outside the airplane, Jon indicates it sounds fine. After checking it several more times, I decide it's safe to fly home. Again, the flight is uneventful.
When I get back to Columbia County, I turn the airplane over to Brian Gaylord. Before opening the airplane, he is pretty sure the problem is with the plugs. They looked marginal when the airplane was in for a recent previous problem that was solved with a prop governor overhaul/rebuild and a new tachometer. Maybe after 33 years my airplane is starting to show signs of aging.
Then comes the phone call.
Richmor Aviation at Columbia County manages and maintains an impressive fleet of business jets, but when it comes to major concerns with piston-engine airplanes, it calls in experts from its other bases. Brian enlisted the help of Joe Femia, a mechanic based at Schenectady, who, as the owner of a Piper 140, is very familiar with piston engines.
Joe tells me that as soon as he started the airplane, the engine ran roughly. That wasn't what I had experienced. With me, the airplane had started smoothly and it wasn't until I did the mag check after it had been running for at least five or 10 minutes that it ran roughly. Joe also says that, while it was running roughly, he did a mag check and the magnetos were fine. After shutting down the engine he went over the injectors and the plugs, and again everything checked out fine.
Although the engine wasn't exhibiting the typical symptoms of "morning sickness," which is caused by sticking valves, that seemed the most likely source of the problem. Brian and Sal, the chief mechanic, were convinced that, considering the age of the engine, and without knowing what was wrong, it simply wasn't safe to fly the airplane.
Not what I want to hear. After much discussion, Sal agrees to investigate further but with the understanding that even if the shop can determine what is wrong and if the problem can be corrected, he will make a logbook entry advising that the engine be overhauled. "With an engine that has high time, if something happens, we'll be exposed, so it's really for our protection," he admits. "And yours," he adds, in case you decide to sell the airplane.
